A Tandem for 2011

Posted on December 25th, 2010 by Dave under Bikes, For Sale, Tandem bicycles.
Tags: , , ,

It’s been a year since the last tandem was finished. It was a success that, fortunately, matched my expectations, but being a track tandem it was a financial nightmare. Link to that build here. Like unicycles, the market is really small and the fixie group hasn’t decided they all need a tandem to round out their collections. So, I just spent another $800 bucks for this pile of very new steel (well, Niobium) tubes from Columbus. There are a couple odd balls, like the round Cromoly boom tube a 9/6/9 (that’s frame builder speak for the wall thickness of a butted tube, er, the ends and the middle).

There are 5 Columbus down tubes used for  the down tube, top tubes and the laterals. Normally they are 0.5/0.38/0.5mm for the Spirit road set.  These are .6/.38/.6  So just a smell more beef at the ends and this should be the cat’s meow for a tandem application.  Bear in mind that this is going to be a

Raw ingredients-stir and bake at 1200 degrees

geared road version with no intention of loaded touring.

Honestly, I’m swamped with automotive work and hopefully now that I’ve put this up for the world to see, it will push me to get started on the work I love the most and take a break from the work that pays the bills every month.   ;~)

Before I forget, again, here’s a picture, nearly an optical illusion, of one of the Columbus Spirit (shaped- not that round Over/Size “for lugs”  stuff the other guys are using)

As you can see it is oval-ized at the ends but the oval rotates from vertical at one end to horizontal at the other. One can also see the 8 sides. It is a marvel of tubing design, should such a marvel interest one…

At the heart of the matter

By the way,  a comparable Carbon Fiber down tube of equal length weighs about 50 grams, these weigh 60 grams..

With all the talk on the various frame-builder forums and chat lists about how to lay down the perfect fillet, try one or two of these on for size. It ain’t in Kansas anymore..

For anyone wondering, I’ll be using Fillet Pro silver based filler for 98% of the joining.  Great product, available here  http://www.CycleDesignUSA.com hope that link works..

OK let’s get this show on the road…

I spent an entire day trying to decide what to do with some of the design elements to come. Chauncey came by and then re rehashed the whole project over again and I finally drilled and tapped a couple new holes in the jig to lengthen the boom tube another one inch. It’s up to 650mm c/c now..

preparing jig for tandem build

Remember, click on photo to enlarge and use return arrow to return to text..

So here are the front eccentric and the rear (stokers) BB shells loaded in the jig and drilled for brazing vent holes.

Choosing the boom tube

Well, I had wanted a full length oval boom, but was unable to get one in a timely fashion so I bought a round 9/6/9 mountain bike down tube at 750mm but, it was too heavy and I couldn’t make myself like it enough to use it, so during the process of wasting the afternoon I found this slightly surface rusted Columbus MAX OR down tube, also 750mm long and I was just informed by a reader that the OR down tube is also 9/6/9.  It is perhaps  half the weight and oval-ized at both ends. Bonus!

front BB and boom tube

So I blasted it, mitered it and then did the other end..

rear BB shell and boom tube

here’s the cold fit look.

cold fitting-pre brazing

It’s time to give a plug to my collaborator from the last tandem.. Thank you Mr. Martin Manning!  Part of the reason I wasted so much time was deciding on some of the attributes I’m hoping for from this more versatile bike. So Martin and …well, it was mostly all Martin,. He made some insertions and changes to the track tandem drawing with his Bike Geometry program. (What a cool tool and its free!) I know there are some other programs out there to design with, but this one is very, very bicycle specific and Martin is so into bike design.

So, this is out of sequence, but here’s the 1 1/8th” head tube at it’s 74.5 degree angle. What? Yes, it’s going to have a 1″ steel, but thread-less steerer.  I like steel and I like to decorate it with silver. Get over it..               Builders note: Turns out that the thread less plan didn’t pan out as expected. It’s a threaded one inch steerer with a Cane Creek mod 100 doing the work load and a Nitto adapter for the stem adapter.. end note.

74.5 degrees

OK, time to get some more heat (and fumes) in the shop. It hasn’t been above freezing here for the last 2 days.. So, here is what I did for the second time. I’ve loaded the ID of the boom tube with 38 percent silver paste. This after coating with flux. The paste has its own but I found that more is better to get the 38% to move a little better. The point here is to create an internal filet at the same time I’m building the external filet..

silver paste "Butter"

Moving right along now..

eccentric post filet

so, here’s the “keel” backbone,

partial "keel"

next the chain stays. And lastly today, while Chauncey was here, he did some practice welds with the TIG on some stainless, like these, except these are mine… not very clear and probably just as well and anyway I don’t think I’ll ever TIG weld a bike frame

TIG'd stainless w/o filler practice welds

So today’s project was to get some work done on the chain stays, specifically the dropouts attached, but no, I out smarted myself. I bought another set of the cast adjustables like I last used on the Mini-MAX frame a few months back.  Well, it was a nice idea, but there is no way, short of S-bends in the stays to get the 140mm spacing needed for this tandem. Oh! How about Keith’s new Tito drops… well, they will bend, but they are a little too short for that and then to still have the finished look I would have wanted. Darn. So, without too many tears I went to the trusty file cabinet and found a suitable set of forged Columbus horizontals… here’s the choices..  (several days later: This just in from one of my growing list of guardian angels, Wayne on the Hobbs Tandem list tells me that the new “conventional” rear axle spacing is 145mm and wider still for Santana tandems- so much for convention ;~)  )


And here is the brazed up stays and drops. I’ll file these next so I don’t have to do cleanup work after the seat stays are in the way to impede access to all surfaces. After they cool, I keep an old coffee maker next to the bench and soak the flux off with hot water, then give them a run through the wire brush whirligig. It would be nice to just leave them in this semi-organic state, but the forgings are so rough I have to file them smooth  for painting. Some may wonder what the big deal is here, well my “signature” seat stay attachment can make the connection at the drop look awkward due to the more acute angle.

Ready for detailing.

It’s late, but I’ll get these up now and explain later……(yawn) morning all. OK- I managed to cut the chain stays to length (430mm) and form the miters at the BB connection (70mm drop). These are triangular shaped stays from the old Columbus EGO sets. These, sadly, were the last two in stock at Nova Cycles warehouse stash. The next sets are going to be difficult to find. I have to drill vent holes in the BB shell and I think I’ll put a couple in the distal ends too. It’s pretty dry here in NM, but generally warm enough to ride throughout the winter months and that means that condensation can be a problem when returning to a warm storage spot or the frame could end up in wetter climes. These stays are closer to Nivachrome or Chromoly so they don’t have the rust resistance that the new Niobium has.

Chain-stays mitered to BB

Dropouts in road drop fixture @ 140mm

Just a shot of the drops loaded into the road drop fixture. It has shims to achieve the desired axle spacing and removable set screws to set the side to side indexing so the drops are at the same angle. There are also some pre-set holes to add rack bosses in the usual spots.


I like this picture. Simple beauty. Enlarge. (click on pix)

Moving along again after a couple  “just touch” with a file as my late friend Pino would have said. The rear axle spacing is up to 145mm and the chain stays are brazed and semi finished. No point in doing too much finish work until the seat tube, guides and whatever are attached as well.  Here’s the picture..

left side

It’s back in the jig again. Normally I’d do the front down tube next, but I’ve decided to add the set or sets of seat stays next. This means the stokers seat tube must be positioned, so I’ll get after that..

I got the stokers seat tube attached and the primary set of  seat stays ready to attach at which time my feet, which I’d already been on for 12 hours in the “other side” of the shop were telling me to call it a day. I just want to point out in the following picture the unusual shape of the Spirit seat stays. They start as the usual round taper at the dropout and then have teardrop/wing sort of 6 1/2″ long section and reverts to round again. The OD is nearly 11/16ths, which is down right big as compared to other manufacturer’s stays. It adds a goodly (technical term) amount of strength.

Shaped seat stay

Building old fashioned steel frames is a pile of work and at some points in the process there are aspects that appear to the uninformed observer as ugly..  some of this next group of pictures is were the process is between the raw weld and semi-finished. To get to the full paint ready condition takes the majority of time. Gross pipe fitting is gratifying to the builder because he/she knows that the weld is correct and that the location of the part is where it should be-sometimes not an easy task. This is more so when lug less frames have no spigots to make the job easier.

Stoker BB

Here the stokers BB is on the 4th weld, the seat post. It still has one more when the rear lateral is added. At each stage I do some shaping of the fillet and removal of the used flux and oxides of combustion that stain the surface.

Niobium and silver

Here’s a real close look.

This next shot is the “signature” seat stay connection before any shaping. This joint was done with 56% silver filler. I need the filler to easily flow into the joints with out overheating the tubes. A balancing act with the torch..

Seat tube and seat stays

The non drive side rear drop is interesting as one can see a tiny piece of scrap that I’d inserted in the weld gap to hold the drop at the precise angle. Some folks use pins or nails or other means. This is easy and effective for me..

Rear drop out

..and here’s the other side..

Columbus horizontal dropout

Now that the rear triangle is attached, I’ve attached the brake bridge. It’s not the one I wanted to use, but after searching the shop for the tried and true Cinelli 506’s for an hour I said what the hell, so I turned this one upside down (I guess- no brake bridge police that I’m aware of) and I’ll doll it up with something when I get to that point. This is also 56% filler.

Brake Bridge

A bit fuzzy

Here’s the mid-seat connection after a little work with a round Riffler file. Looks better already. Darn digital camera gets fussy about focus with out doing the Macro setting which is too close for getting the whole object and the regular  way gets too busy with background stuff..then there’s the flash prompt..geeze.

keeping things moving, I’ve attached or more aptly pre-placed the captain’s seat tube. Here I loaded the ID with silver paste and heated until it bonded with the eccentric shell. This will keep overlap welds to a minimum while the main downtube is being fitted.

Captain's seat tube

I had the chance to buy a full size alignment table from a local builder and the price was good. I don’t really think I’ve had much use for one in the past as my Morroni jig doubles as an alignment fixture, but it can’t hurt to have another nice usable tool. I added casters to it so I don’t have to dedicate too much precious space.

Bringheli Alignment Table

Here’s a new trick. These tubes are really hard to scribe a center line on since the diameter changes constantly from end to end relative to the center line. So what I do is use a carpenter’s chalk line and snap the line. It’s by eye, but that ‘s pretty good. See the blue?

Thin Blue Line

Tonight I cut the main down tube to length and mitered the ends. Spent most of the evening trying to decide the seat tube lengths and placement of the internal laterals. I don’t have a drawing so I’m using my experience and how I think it will look the best.. it’s a personal thing, functionally it’s moot.

Now here’s a couple cuts that you won’t see too often.  I do this pretty much by eye. I’ll hold the top tube more or less in place and using a Sharpie draw the perpendicular outlines of the seat tube. Then with a hole saw followed with the trusty Dynafile cut the top and bottom of the top tube where the seat tube will (hopefully) intersect. The rusty old seat tube is just a way to gauge my progress in the vice until, as below..Top tube/Seat tube intersection-captain's and from the side

gross fitting stage

and lastly tonight, here’s the front half with the main down tube brazed in place. At this point the remaining top and lateral tubes won’t be brazed in place until they all fit and look pleasing to the eye.

New and old

I didn’t get a whole lot done on the frame tonight. I managed to get the rear lateral within an inch of where I want it. The captain’s top tube is also close, but the stoker’s top tube is just sitting on top of jig held on with a toe strap!

I received an old Raleigh in the parcel delivery today. It was bent sideways at the seat stays and I wanted to get the repair done and off my plate, so that ate up some time and I dismantled some of the new alignment table. I was very unhappy with the BB post’s method of setting the shell and the cylindrical jack was several thousandths out of perpendicularity (there’s a mouthful, eh?). Drew G. at the other end of the country recommended buying brass tipped set screws for the head tube “precision bar” so it wouldn’t be scarred with every tightening. I opted for flowing a drop of silver on them, same but different. Good idea Drew. Thanks!  Nevertheless, I’ll add one more picture..

Starting to look like a bike

I forewent a bike ride on a darn nice winter day today because this frame was calling to me. Right now I’m in the stage that is tedious and slow, thus requiring  a weekend afternoon without distractions. Well, all the main tubes are cut and mitered and ready to prep and braze, except for the internal lateral joint on the captain’s seat tube. The Spirit is very thin walled and I will cut some half tube shims to beef up the joint. They are “buried” in the fillet and unseen. So more hand mitering to open the circumference there. (I don’t feel there is any need to repeat that with the seat and top tube since it is effectively reinforced with the seat post.) You can see in the next picture that they sag a little there because its not a close miter and they are sitting on a c-clamp.

Main tubes all in place

This shouldn’t cause anguish, but I didn’t like some of the decisions I’d made along the way. I really need to get this sold, I don’t need another tandem, though one fellow on the Classic Rendezvous list admitted to having eight. It is now a 58.5cm captain seat tube and a 56cm stoker. I wanted a little smaller in the rear, but I reasoned that since the stoker doesn’t have to put their foot down at every stop it would still be an acceptable compromise.

So after cleaning the tubes and lathering with flux I brazed them into place. It’s a done deal now, eh? It’s a Federal holiday today, so I have a legitimate excuse to work on the frame and not on the cars backed up in the driveway, plus it could reach 60F today and it’s time to get back into a 5 day a week riding schedule.

I’ll do some filing on the new welds and try to decide how to address the open ends of the two top tubes at the captains seat, With the MAX I used to continue the tube to the other side then add a flat cover panel. But, here I have 4 flat surfaces just begging for some shiny silver decoration.

Now I remember why its been a year since the last one. They are a boat load of work. I put 10 hours of filing and shaping the fillets in today. My right hand (dominant) was the worst burned in the fire of ’07. The web area required grafting and has always given me some grief, but I must say that spending multiple hours with a Riffler file exercising the thumb and fore finger is excellent therapy. Good thing, as there are  still several days of similar finish work still to come.

I’m very happy with my welds, only two small spots that were not fully to the height of the rest and required going back to fill.. The most difficult was the rear seat/BB/Lateral joint. If you can imagine the thick wall BB and the near paper thin Spirit tubes and then try to flow the silver on the underside of the lateral as it miters into the BB and boom tube. A typical temperature flame will rapidly overheat the lateral and burn it and too cold it will never flow out on the BB or boom. Solution was to flow the under side of the boom first then adjust the flame to a super oxygen hot with a very short flame, which won’t wash over a large surface area, but rapidly heats the thick wall tubes and flowed the silver down very nicely.

All main tubes brazed and shaped

I took a bunch of photos of the individual joints but the flash and reflections made them unusable. Maybe tomorrow with some day light I’ll try again.

The next step is to fill the gaping holes on the top tubes, which I mentioned yesterday. Unfortunately tomorrow is a work day, so maybe tomorrow evening.

Finally had a chance to work on the frame a little tonight. I need to go back and do more shaping on a few of the fillets. Tonight I decided to get after the internal laterals where they butt to the captain’s seat tube. The front lateral is shorter than the rear, consequently the diameters and shape is a little different where they butt. So, the major shape was obtained using silver, but tonight I filled some of the low and mismatched spots with lead filler. I like the lead because it goes down at about 300 degrees F.  It’s very soft and easy to shape with a file. I also don’t need to worry that flexing of the frame will crack it off, like Bondo or glaze might. Here are a couple ultra close ups. So close the file marks from the jewelers files look like canyons. The  lead is slightly darker than the steel. The yellow is the silver. These still need some emery and then primer and blocking will take care of the rest..

Right side

Left side

I felt like I left this subject hanging last night, so I took a few moments this morning to finish/sand the joint with 320 grit cloth and hit it with some flat black rattle can to see where I am in getting it looking like I want.

These tubes do more shape shifting  and have more metal contours than I usually deal with. Anyway, this is getting close and I’ll just switch to a glaze to eliminate any visible feathering.. The lead is really superior to plastic fillers but, it requires another level of supplies and expertise.

Left side-pre blocking

Right side pre blocking

I decided that the ends of the top tubes were not going to fix themselves so I cleared the bench of the heavy tools and pulled out the jeweler’s stuff. I’m running low on some of the silver sheet and I’m running low on ideas.

I decided that a nice silver Oso (bear) fetish would look OK on the cover, then I decided to do an overlay, then I changed my mind and decided to put a stone bear over the silver overlay and antique-ish the edges. Well, after nearly a half day of messing around I have this..

Captain's seat back

For the head badge I decided to keep it pretty simple. All silver.

Head tube badge

I see its been six days since I added any content to this posting, But I have been hard at work on this tandem all those days, well nights at least. I have worn my fingers thin sanding and re-sanding and then re-sanding a couple more times. I haven’t bothered with glazing putty for ages and for good reason. It will make you crazy trying to fill every file mark or imperfection. That’s why they’re “hand made” for Pete’s sake. Anyway, its as smooth as I’m going to do. The braze-on’s are on and most of the silver work is on. I didn’t post pictures of this as its pretty rote stuff. I’ll finish the last silver bit tomorrow and then get after the fork. I can see the light at the end of the tunnel. Yah!

Here’s some pictures without any explanations..

Lesft side with blocking showing

End caps and silver bridge work

Front to rear perspective


Bottle bosses

Last turquoise piece for the stoker

It’s been below 10 degrees F for the last two days, very unusual for Albuquerque and way too cold to work on cars, soooo I went to work on getting the fork done.  here’s the steerer and crown while still warm..

Crown and steerer joint

As I mentioned earlier in this article, I am collaborating with Martin (Bicycle geometry 101) Manning. He has  suggested a rake which results in 45mm of trail. I must say that I’m a little concerned. I’ve never built a fork with so much rake/offset as this one has. I was always happy with the handling when the trail was between 2 and 2  1/2 inches . This is about 1 7/8 inches of trail. Martin’s theory is that this will impart more low speed stability. One has essentially twice the force on the lever arm created by the trail, which makes tandems hard to handle at start-up and when climbing a steep hill.  Those situations are hard enough due to the rider coordination required.  They go fast, too, so the high-speed stuff can’t be ignored.  He believes the better compromise is to accept a little less stability at high speed in favor of the low speed operation.
Here’s the blades loaded in the jig with 47 mm of offset..

fork jig

And lastly today, here is the finished fork in the frame…

Frame and Fork

OK, time to think seriously about paint colors..

Well, after about two seconds of consideration and the fact that I have a full can of the green I painted my own bike with, here it is,  awaiting components.  Signal green Imron frame and fork…

front triangle and fork

back to front view

seat stays with turquoise

The whole enchilada

That about wraps this up. I’ll get it assembled as soon as I get all the “stuff” and then post a few pictures and an evaluation of its performance.

This project took over a month to complete and that was working on it very nearly every day. I haven’t decided on pricing yet, but no doubt it will be less than the effort expended.

Stay tuned in…

Comments (2)

Mini MAX a pictorial review

Posted on August 6th, 2010 by Dave under Bikes, For Sale.
Tags: ,

Vortex generators?

Vortex generators?


Columbus Mini MAX  63cm with turquoise and silver detail. Silver fillet brazed.


Seat stay connection detail.


Bird on a wire…

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Silver Paste part II

Posted on January 20th, 2010 by Dave under Bikes.
Tags: , ,

Here’s another application for the paste silver.

This is a new frame using the spigot style drop outs from Nova Cycle Supply (www.novacycles.com).  I  dabbed  about a 3/4″ line of material inside the dropout then spread it  around evenly, stuck the chain stay in, added some extra flux on the outside in case I didn’t start with enough paste and had to add regular rod style filler.

Click & double click photos for close up…

Paste flux and filler post heating

Paste flux and filler post heating

One can see that a small amount of the paste has migrated to the outer surface of the drop. There were only 2 spots a couple square millimeters that had to be filed. All subsequent clean up was done with polishing compound.

polished drops

polished drops

Worth noting here. As you can see, plain steel (not SS) can look as good as SS for less money and will retain it’s luster for a surprisingly long time between buffing up (like a year in the SW climate).

The next two photos are the chain stays to BB welds. This time I put paste inside the tubes (stays and seat) to form a small internal fillet and used rod on the external fillets. I’ll put up a picture of the entire finished joint after the down tube is mated.

Welds #1, 4 and 5

Welds #1, 4 and 5

I  mitered the down tube and brazed it in today. Again I lined the inside of the tube with paste and used rod filler for the external fillet.

Mitered down tube

Mitered down tube

Post brazing

Post brazing

Post shaping clean up

Post shaping clean up

Now, the neat thing about the butter is that I can even further reduce the size the external fillet because there is now an internal fillet to support the joint.  Here is a shot of the head tube joints. The fillet radius is tiny now. If these were regular round tubes it would show better than with the Spirit 8 sided tubes, but you get the idea.

Internal and external silver fillets

Internal and external silver fillets

Remember to double click to get super close up. Use return arrow to return to text.

…and we’ll jump way ahead and here’s the frame in it’s ready to be built up state.

Click & double click photos for close up…

Zia frame

Zia frame

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New tandem project

Posted on April 17th, 2009 by Dave under Bikes, For Sale, Tandem bicycles.
Tags: , , , , ,

Nearly 20 years ago I built this tandem as an experiment. It was made from Columbus MAX road bike sets and a generic oval boom tube. Here’s a picture of it’s current dirty-dusty state, in the equally dirty-dusty crowded frame building corner of the shop.   (Click/double click on photos to enlarge)

As you can see, it has old components, Mavic drive train, down tube shifters (7spd freewheel), Campy brakes, no name levers, in other words it’s just equipped for general around town riding. It does have track dropouts with a derailleur hanger.  But, it’s main intended purpose was for track use. Perhaps, you’ve heard my story about Track Nationals, the USCF, and this frame set. I’ll add a condensed version of the story later.

(The story)

When Columbus MAX was first introduced I just fell in love with it. Light and strong and steel.
So, I decided to build a tandem with it, even though it was not recommended. Well, it was amazing. A little over 30lbs and wicked acceleration with a couple strong riders.
So, I thought I’d ask the USCF Nat. coach if he had any interest in using the tandem at Nats which were being held at Trexlertown that year. He said “yeah Dave get it to so and so in San Diego”, as they were the two hot tandem riders. I duly delivered the bare frame to these guys and drove back to NM.
In those days the only source of racing news was Velonews. When I read that the tandem these guys were riding at Nationals had broken and they had to borrow one it was a huge slap to my reputation/ego. Or so I thought. Well,…as it turned out, these guys had never even assembled or ridden my tandem…. Slap number two.
I tried for over a year to get the frame back. I finally sent the USCF an invoice for $6000.00 and it miraculously appeared back at the shop.
Needless to say I was miffed that after all my expense and effort it remained untested. So, at the next Nat. road TT in Moriarity, NM, I added a derailleur hanger, shifter bosses and brakes and gave it to a couple of the shop team riders for the event.
Result..gold medal. Every event its entered since then it has won gold, except the last when the age graded riders missed the gold by 9 seconds. (90+) It still holds the National record for Cat I men. 44 minutes some seconds set in 1992 I think..

National Tandem TT champs

National Tandem TT champs

Very cool I think and great redemption too. It’s been used by juniors, seniors and mixed gender too.
Well, that’s the story.

I was just rooting through my desk drawers and found this letter. Funny, I don’t remember the check, only the frame coming back. I don’t remember, it gets worse with age..

Click here tandem-fiasco

click back button to return to blog..

It’s a very compact design, due to the fact that the MAX tubes were made in only road bike lengths. It’s a 75 degree HT, 74 degree Captain’s ST and 72 degree Stoker ST. Wheelbase is 1645mm and the boom is 615mm. BB height is  10 1/2″ rear, 11 1/2″ front BB.  Captain’s seat tube is 56cm, Stoker is 57cm  and top tubes are 58cm and 61cm respectively.

The stem is a custom adjustable length and employs a “stayer” brace of Titanium. The fork is one of my signature “aero” designs and has special skirts at the drop outs for wind drag issue.

Since building this one, there have been more huge leaps in the steel technology available for bicycles. So, since the economy is slow, meaning my automotive restoration business, I decided it was time to test some new materials and to try out the new tandem jig, which in a previous blog story I explained building a single frame on.

I’ll do the same for this new tandem in the following entries. “Squirt II”  (authors note: It seems to make the project more tangible when it has a name)

Yikes! Here’s over $800 bucks of raw materials..

and here is the jig configured for a tandem build.

Ready for the first two welds.

The “keel” is laid. This stage forms the backbone of the tandem frame. This stage was done using brass. This was done so that when the seat tubes and down tube is added I can use silver and not disturb the older welds. All of these five pieces shown are the thickest wall and not much bothered by the additional heat.

Oh My God! There I go again. Cutting big holes in a perfectly good boom tube. What was I thinking??

Here’s what I was thinking. I made two slightly off set (front to rear) holes through the boom tube and inserted two wing shaped inserts. The general idea is to help resist twisting of the boom. I probably should just finish them flush with the boom, but I think I’ll let them protrude like this just to add some interest. Not much to look at on a track tandem..

In this next picture I am what one would call “committed to the steering geometry”. I will interject at this point that I am having one of the guys from the bike builders e-mail list collaborate with some of the design work. He is an engineer, I’m a self taught guy with a lot of years experience. I thought it would be interesting, at least for me, to compare notes in a manner of speaking. I’ll leave him nameless for now, to protect the innocent.

The down tube and head tube are now joined thus completing the “keel”. Everything goes up from here. These are the first two silver fillets. The next picture is for Mr. Garro. I’ve washed the flux off and just rubbed it a bit with steel wool. The head tube won’t get much, if any clean up, until the internal lateral and captain’s top tube are fitted. Those fillets will be blended together to minimize the head tube height as the tubes have a vertical dimension of 43.5mm each and I’m trying to keep the head tube at a minimum.

Between multiple distractions today I was able to get both seat posts welded down as well as the stokers top tube.

The tricky part is the top tubes. This old jig was designed for 1″ round top tubes. This Columbus tubing is 43.5 x 29mm and is 8 sided, plus the oval rotates 90 degrees from end to end. Needless to say, it would take a handful of various sized blocks to hold the tube, so I just turn the entire top tube holder assembly upside down and set the tube on it’s machined surface. A couple measurements and some old toe straps and it’s good to go.

Oh, oh! The stoker’s  top tube is too short!

Yeah, well it was part of the plan. Really.

Like the MAX these tubes weren’t designed for tandem use.  I wanted to increase the stoker cockpit over the old tandem.  The captain’s top tube will appear to be pierced by the seat tube and the two top tubes will be butt welded. That will take some time and will be repeated on the internal laterals. Both the riders will have an additional 3cm of leg room, this is good.

Here’s how it works. Here is the cold fit stage.

I thought I’d try these new fangled track drop outs.  Already I’m thinking it was a bad decision as I want to attach 2 pairs of seat stays and there is limited room to do so. I’ll ponder it a while. There may be a clever solution, may be not.

The first set of seat stays and the bridge are on and now I’m not sure that I want to add a second set as planned. The triangular chain stays are naturally rigid and the three point attachment on the seat tube is a bit stronger (?) than normal and the lower attachment on the seat tube makes a smaller triangle too. I’ll have to think about it some more. I don’t know about the rest of you but sometimes I’ll just sit there and stare at the project at hand until an idea strikes. This may be one of those instances.

It’s one of those days that looks like it will snow any minute, but still a couple of degrees too warm. So, I’ve decided to use my Sunday working on fitting the internal laterals. I have it fit up pretty close here, but it needs just a couple touch’s more to get alignment and gaps the way I need them. Since the seat tube is only 0.38mm wall thickness where they intersect, I brazed a couple of split scrap pieces on the seat tube, which I’ll bury under the fillet. I also left a larger than normal perimeter gap that I’ll fill with silver. These tubes are pretty brittle and I think if they don’t actually butt up that movement in the filler is superior to contact of the tube ends. I’m hoping that it will keep the paint from cracking too.

That little coil of silver hanging from the jig is all I have left. It looks like I might not be able to finish the brazing until I get restocked next month. Maybe Santa will be good to me this year.

It’s Christmas day.  Presents are opened and the belly is full. Life is good.

So, yesterday I finished brazing the remaining main tubes in. I had to mix some  Brazage Pro and All-State 45%, which I was told was OK to do. (we’ll see) I’m confident that the joints are structurally fine, but I was being so miserly with the silver that there are a couple “rough” spots in the fillets.  I’m torn between leaving well enough alone and going back over the spots to fill with additional material. To get it hot enough to accomplish this is probably not worth the risk of heat damage to the overall structure. Some “filler” primer will make it look fine. Above is the rear BB and chain stays. That’s a 22mm tire shown, we’ll use a 19mm Continental Olympic when it debuts on the track. (220psi for a mere $300 a piece).

Here’s the front BB and eccentric. The only thing left is to install seat tube binders (2 on each tube) and to split the eccentric shell and add binders to it. Oh, the head tube needs to be trimmed to length and reamed.

The frame is weighing in at an amazing nine pounds, so I guess I’ll splurge and add a tiny bit of silver smith decoration on the connecting tube between the seat stays. Perhaps a couple nice bits of New Mexico turquoise as I’ve done before. It’s only a few grams, and it makes it oh so regional.

I only have the fork to finish now. I’m definitely out of silver filler, so now I’ll get on the phone and start shopping for some components in the mean time.

The specs so far are: Wheelbase 171 cm; captains seat 57 cm @ 74 degrees and a 63cm top tube; the stokers is a 57.5 seat @ 73 degrees and a 64cm top tube. BB drop is 5.2cm The head tube is 76 degrees with a 40mm fork rake planned.

This is the finished but unpainted frame. Tomorrow I’ll make the silver adornments to doll it up a little. Hope to have the supplies to make the fork soon. I put wheels on it today and stood on the boom tube and it seems to be plenty strong despite the light weight. I would not recommend trying to stand on one of the top tubes though. They are deformable with the thumb and fore finger. Maybe some ” No Step” decals like an airplane are in order.

Squirt II

Squirt II

I’m thinking about painting the frame all in a bright silver metallic. But, I’m always open to suggestions…

Here are the two silver cups to hold the turquoise stones which will be brazed on as stay caps. Very New Mexico.

Stay caps

Stay caps

Yesterday, I followed through with the silver decorations.  I went a little over board with the head tube badge.  It’s my standard “P” with a nice piece of Arizona turquoise in the “hole” of the P and at the base I made little doodads to represent Chamisa plants with some stylized fronds. It’s on there now so love it or hate it.

head tube badge

head tube badge

and here are the turquoise caps on the seat stay connector tube ends.

Santa Fe style

Santa Fe style

left overs

left overs

Oh, oh. I’ve got left overs. To tell the truth, this one was so much fun maybe I’ll do a road version next and save this set of seat stays for it.

Discarded tips

Discarded tips

The forks were a bit of a challenge. The blades are aero shaped and to get the desired length I would have to have cut virtually all the wing shaped ends off. And that shape was the whole point. So to get 40mm of rake I started curving at the distal ends and slowly and carefully moved up the blade. A bit tricky with a non round shape. Anyway, here’s the cut off ends. Needless to say the dropouts fit entirely into the ID of the remaining blades and requires a lot of brass to fill. But, they are nice and beefy there and should handle the tandem weight demands without problem.

Aero fork

Aero fork

The finished forks.

On the ground

On the ground

A few details left, a little more clean up, headset machining and paint. It’s too long for my new paint booth so I’ll take it to a friends car booth after the New Year holiday. Anyone happen to know if the UCI has a minimum tandem weight? I’m really excited to try this out. Unfortunately I’ll have to wait until the Spring to go up to Colorado Springs.

To be honest, the more I stare at the frame and every  time I pick  it up I get the feeling in the pit of my stomach that it simply is too light. Now I know that Calfee has a bamboo tandem and there are some damn light Carbon Fiber tandems out there but I still don’t have a warm fuzzy feeling that this will withstand the rigors of the velodrome with two world class athletes aboard.  I’m thinking about adding an additional internal lateral to the stoker’s main trapezoid, which will also give an ideal location for an additional set of seat stays. Perhaps I’m jumping the gun as it hasn’t even been ridden around the block yet.  Any suggestions??

Well, I chickened out and added another lateral to the frame yesterday. Also added some little 3/16″ SS tubes to the rear triangle. I saw them on one of Pino’s bikes click here:  and not knowing of this technique previously I thought I’d give it a try since I was on the fence about this too.

4 more tubes

4 more tubes

Additional stays are hardly noticable

Additional stays are hardly noticeable

paint and parts next

paint and parts next

I was still feeling nervous, so decided to try something new, I think, and radical, I think. So, what do you think?

All trussed up and no where to go...yet

All trussed up and no where to go...yet

I was told that the stokers BB gets four times the stresses of a single frame’s BB. So since this is already bolstered on the top, I thought I’d beef up the under side with this truss like contraption.

I’ve received a fair number of comments on the “mid-stay” tubes  usefulness. The jury is still out on that one. Another builder on the “frame-builders” list also pointed out that the curved truss under the BB is a poor design. I knew that, but did not want to spend an inordinate amount of time making miniature lugged spigots to use straight chords. It is a bicycle, after all, not a 7000 HP dragster.

More to come in the coming weeks. The riders need to do some shake down and training rides now that the weather is starting to cooperate.

I haven’t been able to find any real sponsorship from any of my old sources. Used to be they were happy to provide parts in exchange for advertising. Only Shimano was willing, but unfortunately they don’t have the necessary tandem parts.  This may have to come all from my own threadbare pockets. Oh well, been there before.

As of right now, we are looking at a date to coincide with the NM Track Championships, June, I think.

As soon as the riders are happy with it I’ll get some paint on it and post those pictures. Should be a handsome tandem, IMO of course.

March 20th, the two prospective riders and I all had our schedules in perfect alignment today and we got to give Squirt II and 20 mile test run.

Well, the bad news is that I can’t go that fast anymore! They could drop me like a rock. The good news is that even with skinny width road bars the captain was very happy with the handling. The Stoker was equally happy that his position was identical to his road bike, except for the bend of his bars.  The frame was absolutely rigid and dead quiet. Very cool. Next week we’ll change it to a 49 x 17 gear for better flexibility around town and then work on some position nuances for the guys.


Here’s how it looks for the 1st official test ride.


I was hoping the “truss” was visible on this side but, not really. At any rate, while on the wheel going down the street I asked the guys to stand and sprint for a few revolutions to see if there was any discernible deflection of the rear triangle. I couldn’t accelerate with them for very far and I saw no movement at all. We did the same thing at low speed on steep grades. No flex! I was a happy camper.

Finally decided on a color scheme.  Here’s some pictures post paint and decals.

Click on pictures to enlarge.

Squirt 2 in paint

Squirt 2 in paint







The brake is for around town test rides. The Campy headset and TA cranks make it On Topic for the CR folks, yes?

It’s a Lt. Violet metallic with Silver met. over spray and clear coat. Imron by DuPont.

More to come, check back from time to time and thanks to all the well wishers who have contacted me.

Jump ahead about a year… Frey has contacted me and wants to know if Squirt II is available for the annual Paula Higgins Memorial Record Challenge out in Moriarity New Mexico. I explain that it is currently on consignment sale at the Bike Coop and has been stripped of most of its parts, but sure why not. I need to get it out there in the public eye and also to see how it runs in a competitive setting.

Photo: John Price

Well, the results were pretty good, all things considered.

John picked the bike up on Thursday. Added wheels, seats and what not. Selected a training gear and did a Friday ride with his stoker, who had never ridden a fixed gear before.

Sat. he did another shake down ride with a different stoker and Sun. evening before the event John and Randy did a ride on the actual course.

John did not have the best gear choices, so he went with a 60 x 13 that he used 18 years ago to set the tandem record.

It was unfortunately a crossing headwind out and the same coming back. Their competition were a long standing team of National champs ( I’ll probably brutalize the spelling here, Nico Toutenhoofd and Jim Dickerson.) Who also had a very custom tandem (Dave Tiemeyer) with triple crank set and better suited for a wind hindered ride.

The winners managed a 48 something and my guys were in with a 49 something. John thought that with a bit more training, a better gear, and faster start and turnaround (fixed gear) that they would have beat them… well, perhaps next year eh?      http://www.youtube.com/watch?v=th9Xepc72A8


here’s one more picture..

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Customers bikes

Posted on March 17th, 2009 by Dave under Bikes.
Tags: ,

The stimulus money still has not arrived in my corner of the world and thought I’d scan some photos into the computer just for grins.

For a long time I carefully documented each frame-bike and the customer’s info, then for a long time I quit documenting as the retail end of the business consumed huge amounts of time, which relegated some tasks to the circular file. Here’s a sampling of some of my early work.

Click to enlarge photos. Click again for super size and fries..


These first three are: A Columubus SLX with full Campy group and arguably one of the first paint over weird design stuff paint jobs. Next is a 3 color fade MAX frame with internal routing of brake cable. And last in this group is a Columbus SL with brass details.


In this group are: a two tone track frame of Columbus PL ( an early Fixie, as it has H2O bosses for around town use),  a Columbus Air set with chromed fork and black anodized Campy group, then a 26″ wheeled tri-bike of clear coated MAX and lastly a MAX OR mountain bike (mine) which I still have and still don’t ride much.


The red TT bike is a bunch of assorted tubes I wanted to use up. Close inspection of the fork will reveal my earliest prototype of wind control of spinning wheels. It was/is essentially the same concept that Lance Armstrong’s aerodynamist  John Cobb subsequently did.  I recall sending a letter to Cobb offering some help on this and they responded with ugly letters from some Swiss law firm. Needless to say, I withdrew my offer.

The gray Pursuit frame has 45 assorted holes, actually perpendicular tubes, through it. Not something to ride on cobbles. It’s soooo stiff.

The last two are a tiny 48cm MAX with no toe clip clearance and another early frame with Letraset  decals and more early on brass inlay (fork crown).


Here’s a Black and White of the 1st hand made mountain bike in New Mexico. It was called the X1 …


Here’s a shot of a gaggle of Porter’s on the back porch of the 1st bike store..


This was my bike, for a while. It has the campy 50th Anniversary group.


This one is a hoot. That’s me on the door stoop of the 1st location of the Harvard (street) Bike House. The building (house) was shared with a used book store. About a block away from the University of NM. Across the street from the Purple Hippo, where Susan from the Seinfeld show used to work.


I’ll add more as time and desire permits. Enjoy.

Here’s a 80’s TT frame (Columbus AIR) that showed up on my doorstep today for a repair on the seat clamp. A common problem on the aero seatposts which had poor clamping.

I’d forgotten about this whimsical paint scheme.

Aero TT frame

Aero TT frame

from the back..

from the back..


Comments (2)

Aero frame & fork

Posted on November 23rd, 2008 by admin under Bikes.
Tags: ,

As promised, I’ve reunited frame and fork of a frame set that I always liked. It, unfortunately, never reached it’s possible potential. The rider, while on a Sunday training ride (his road bike) with the T-town guys, either crashed on his own or was helped ( I like to always add some speculation). So, his Olympic Pursuit trial the following day  was done in a good deal of pain. The bright spot, I guess, is that he managed a 6th in the Points race later in the week, which is all the more tribute to the rider and what is clearly not the best choice of bike for that event. It went to State track finals last year (2010), but was viewed in a poor light by the commissar’s. I was told that it “spanked” a lot of newer and lighter equipment. That is pretty reliable hearsay.

Here’s the general idea. It is Columbus EGO tubing. Mostly wing shaped. The chain stays, as I recall, were available in a couple of different shapes. I choose to use the triangular and have the fattest  side up, so it would help with the chokes, (actually these are venturis-note the cable guide air intakes on stays and the “calibrated” air jets in the choke tubes. Got to love those fat seat stays, even when they’re upside down.

It has a 101cm wheelbase, 77 degree seat, 74 degree head tube, 1.5″ rake (for stable steering on the measurement line) and a 10″ BB height.

These stays are wonderful for track use. They are so stiff, I was able to get the wheel very close to enhance the chokes effectiveness but, not worry that frame flex would cause tire rub. Luckily, that’s not much of an issue on a relatively smooth track. The tire shown is not original. We used Falcon ACCEL stretched Kevlar wheels with Continental Olympic tires.

Everything was done to keep the frontal presentation to the wind to a minimum. The top tube was kept as flat (parallel to ground) to decrease frontal area as the overall seat length would permit under a powerful rider. This is a constant in my racing designs, where the stays and top top rarely meet at the same point on the seat tube.

Here’s one of the old 60mm hubs. A Suntour Superbe. Double discs were used for the actual event.

Here’s the skinny frontal area. This has always troubled me some. Is it better to widen the spacing and just let the air pass through or close it down and use mechanical means to control drag?

This is the “business end” shot of the multi-choke concept. By the way, inserting tubes through tubes like this makes for a really stiff fork and decreases splaying in hard turns, Be careful if you try this, though. It can pull the insertion welds apart if you don’t use the right stuff, and I’m not giving any of those secrets away to my competitors. This one is illegal nowadays, so copy away if you want.

One can see the “calibrated” holes inside the chokes and the air inlets behind the BB shell. Well, they were, looks like some rust has changed the shape a bit.. It was painted black to help hide some of the trickery. Too bad because black looks heavy. A nice light blue metallic always helps the rider psychologically.

Well that’s about it. Have at it guys. Show me your better mouse trap. Incidentally, the frame was nicknamed “Squirt”  in reference to, well, one more squirt, if you get the drift…

One more caveat, This sort of bike is not for the casual customer. To make the details function, the bike must be ridden at over 28MPH.  Turbulent air starts at about 60MPH. So, that means at least 30MPH to get turbulence at the top of the spinning wheel.  I can just manage 26-27MPH for a couple of miles with someone chasing me. Not my cup of tea anymore. I should clarify a bit here, air can be turbulent at lower speeds, but it can remain laminar or in contact with the frame up to 60-ish MPH. All you theorists will argue that point , but my source was one of the smartest Indy car designers ever. I trusted him then and now, so get over it.. ;~)

Hope you enjoyed the pictures and oh, I’m working towards another unique frame set for a rather obscure record attempt. Know any really strong riders? See “new tandem project” herein..

Dave 11/23/08

Here’s another in the same vein. It has 45 holes through various and sundry locations. This was one of the, “well let’s just let the air pass though” versions. There’s another around here somewhere that had an eccentric BB so we could change the relative seat angle. I think that Kent Bostick’s wife set a Kilo record with it but the guys never liked it too much.. I’ll dig it out anon.

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