rodar y rodar

I haven`t seen anybody else do it this way (maybe there`s a reason for that ), so thought I`d share this with you in case somebody else can make use of idea. This is I think the third stem clamp I`ve made this way, and I`ve done a number of other misc clamps by the same general method. The positives for it are that it gets the bolts in very close to the tube being clamped and that it`s almost impossible to have anything crooked. Ends up looking pretty cool too, IMO. On the negative side, it`s time consuming and it pretty much requires a lathe and mill. Pardon the crappy pics- I tried.

1. Turn and bore the shell at the end of a piece of stock with enough left over to chuck or clamp. Cut the final OD, but leave the ID a little under. In this case, it was for a 26mm stem and I wanted .050 wall, so I cut the outside to 1.125 and the temporary ID at about 1.010

2. Work out where the center of the binders need to go and vise or clamp to a milling table, locate center. I leave .010 to .015 meat between the major dia of the binder screw threads and whatever it`s clamping around, but in theory it could be as little as zero if you`re brave.

3. Mill pockets for all the binders with an endmill the same size as the stock the binders will be made from- for me, that`s usually either 5/16 for 4mm screws or 3/8 for 5mm screws. If I`m using 3/8 for the binders, I`ll cut the pockets with a 10mm endmill to give a little extra flow room for brazing- 5/16 and m8 are so close together that it doesn`t help much, so I just use whichever. If you stop cutting down before the bottom of the pocket exits the shell, it leaves a little lip that works just dandy to ensure that all the binders are at equal heights when you go to braze them on. I hope that makes sense- my pictures don`t show it very well either. Make a purdy hole in the center of the cap if you`re so inclined- it looks extra cool if countersunk.

4. Measure the height of the pockets, cut and face rods for binders, drill through to tap drill size for the screws you want to use. Sometimes I leave the tops of the binders sticking up a little bit, sometimes just go to the top of the pocket.

5. Dry clamp and check, final clean up, flux, clamp for real, braze. For a single bolt (like a seat post clamp), it`s easiest to just set the binder in the pocket and put a weight on top for tacking. For pairs of binders opposite each other, I made clamps to hold them in place.

6. Soak and clean, go back to the lathe and bore the final ID. Part off.

If there`s no more brazing or welding to do, I`ll slit the shell at that point, then tap the threads and drill out the through holes in the cap to accomodate the screws. Since I still have to braze this one to the rest of my stem, I`ll take an adjustable reamer to it after brazing, and then slit and finish the holes. Yeah, a lot of steps, but for the small number of clamps I have to make I can live with that. What do you guys think?

EDIT: a few tips-
To figure side to side locations for the pockets (center of shell to center of pocket), you can use (D+d)/2 + m where D + tube (bar) dia, d = screw dia, and m = "meat" between the two.

For end to end distance, it helps to leave a little extra space between the binder and the end of the shell (1/32 is nice).

The thicker your shell wall, the deeper you can make the pockets and still have a lip to push the rods up against.

I just use solid roundstock (cold roll, usually) for these because it`s available and easy enough to drill and turn to any size under the sun. Mine are all thick walled, so I think pretty much any steel is strong enough.

Don`t try to make biners from drillrod! After you braze it, you`ll never get even the first hole tapped without breaking off the tap! (trust me on that)

If you sart with stock that`s way bigger than the shell you`re making, be sure to cut the OD long enough that the shoulder doesn`t get in your way when you braze. Also nice to cut the ID a little longer so that you aren`t brazing right next to a heat sink. BUT if you have a lot of thin walled shell sticking out, the vibration makes it tough to machine smoothly.

For the binders, you can use rod smaller than the head of your screws, but the rod sections need to stick up higher then (so the screw heads clear the shell), and that ends up looking kind of unballanced.

I tried a few of these with aluminum and they tore apart- problem is that welds don`t sweat in to cover all the inside surface like braze filler does.

unterhausen

Thanks for the detailed post. I like your fixture. Not sure what to say about the method itself. I think you might be happier long-term with 4140 rod, but I'm not sure it will make any difference.

I would really like to see an explanation and process pics from building the rest of the stem.

DEW21

Custom made part porn, gotta love it! Nice work!

ksisler

Rodar; Your jigging, machinery and machine work is awesome... The basic quality build attribute from your method is that it moves the binder bolt in a close as possible to the center-line of the clamp and thus significantly reduces angular stresses and any distortion to the clamp. At least in theory the resultant clamp bolts should require a good bit less torque to achieve the same degree of clamping capacity...which is very good idea.

Should note that I have seen the result/effect before (but certainly not the quality you have brought to it which is mind boggling!)
-- In the 1970's there were occasional failures with tandem ECC's bottom bracket shells which used two binder bolts to span the cut in the shell and clamp the eccentric in place after adjustment of the timing chain. Never saw a failure on a Taylor or Motobecane, but repaired several lesser brands. Most seemed to have failed due to gross overtightening but found a few poor welds also. The repair was to torch off the binder tubes and use a round file (3/8" or so) to deeply groove the shell before setting a new pair of binder tubes in place and fillet brazing it up. When I did these repairs, I would really groove them in deeply and after brazing I would have to have a go at the inside of the shell with a larger file to remove the part of the binder tubes which hung down into the inside of the shell. My rationale was that it moved the clamping bolt more in-line with the shell housing. Now days I would considered TIG'ing up the gap in the shell, machine it to clean up everything and then install a Bushnell ECC.
-- In the mid 70's myself and a few other multi-seat builders I knew embedded a chromo tube into the frame right behind the Captain's seat tube (at an up angle) to form the base of a stokers stem. All of the ones I did or saw seemed to have the binders embedded pretty deep into the tube (which was usually a trimmed-off nubb'in of HD Reynolds 531 top tube). And it just looked better embedded than just having the binders stuck on the top. As you noted, alighment for brazing is a lot easier with your method (wish I have access to your machinery... am still just licking it with a file). Then we would make the other half of the stem to fit the stoker's length and/or angle needs. Sometime we included two or more at different lengths if several stokers were expected. For me the brazed in stem was just a special touch, was much easier and was cheaper than buying a steel or alloy stoker stem (and still so if you have looked at the prices for them recently).

Live Wire 

The binders look great! You lose strength not having the full braze contact between the shell and binder, but as long as you have you have that beefy fillet on the outside it should be fine.
Personally, I prefer the bigger fillets, and the closer bolts will really make for a slick integrated look when its painted.

MassiveD

Actually the reverse is true. It will take more clamping force, but I like it. The further the boat is from the certer line the longer the lever arm. However, often on cheap bikes you get flex, or even fatigue failures on that kind of structure. With properly machines screw fits, the power required is going to be minimal anyway, to make that thing stick.

On U's point, I never really know what parts have 4130 or not. Obvious from the better suppliers, or if marked, but a lot of parts aren't marked. Regular mild steel is sure strong compared to aluminum. Bar is better than cast.

rodar y rodar

Thanks, guys.

Unterhausen: If I can get the camera away from my wife again, I`ll post the rest of it. Nothing too exciting, though- more a combination of Flitstones and standard machine shop practices than anything you`d see from a bike torch pro.

Ksisler: um... I really appreciate the praise, but it`s entirely unwarranted. I enjoy making things in general, and have a decent grip on a lot of aspects of metal working, but a far cry from a master at any of them. Thanks for those examples of similar applications. Though I was sure it had been done before, I hadn`t seen any, will continue to keep my eyes open for more examples.

I just got a new work order last night that will keep me busy making a big batch of spare parts for stock, so won`t be able to play Bikeman for a few days. Hopefully will get back to it mon or Tues, depending on how many repair calls interrupt the fab work. Sure hope there aren`t many because the adjustable stem I have on my "new" bike now is over 700g and I really want it gone!

rodar y rodar

For the upright quill, I used 7/8 x .050 CroMo. I have a long aluminum V-block with clamp holes on the top side and a 30* slanted bottom that I just slap into a vise for cutting the angles on both post and wedge.

Since I`ve always used super thick tubing before, I had to add an extra step this time. I figure the .050 by itself would eat into the aluminum wedge, so I brazed a piece of 1/8 plate to the cut portion on the bottom of the quill post then put it back into the angle jig and milled it flat. Then to the lathe to make it round again and cut a bolt hole with a broken off 3/8 end mill. The tubing warped a little bit, so I had to file a little bit after turning in order to get all the excess plate out of the way without gouging into the tube.

For the wedge, I turned the OD, drilled out a hollow in the middle (1/8 wall), and tapped on a lathe. Brought it to the mill to flute a little bit (not sure if that`s necessary, but all the commercial wedges I`ve seen have been fluted) and chopped the angle. Then back to the lathe again to part off.

unterhausen

thanks, that was a very informative post. I'm jealous of your collet chuck. I keep thinking about haunting ebay until I find one that fits my lathe, but have never done it.

rodar y rodar

Actually, I had to remake the shell before I could put it all together. I noticed that one of my binders wasn`t brazed completely- it even shows up in the pictures posted above

I don`t have end mills or hole saws suitable for mitering these sizes, so I just filed them. Used the Tim Paterek`s ST to BB jigging method to tack the shell to the extension- set shell in the miter and weight with a little piece of scrap rod.

For the lower joint, I clamped the shell to a flat piece of plate with a washer, worked out shims to keep the quill post on center and clamped that all up. With the joint off the edge of the steel plate, it leaves plenty of torch room for tacking both sides. The extension is 1 X .035, and I didn`t like how it fit up against the 7/8 part. in the future, I`ll go back to using the same diameter for both parts.

Since the longest stem bolt I could find was still way too short, I made a little inverted cup and brazed it in place through a couple of small holes drilled through the post wall. The bolt head ends up a couple inches below the top, but I can still reach it easilly with the long end of a stubby L-shaped allen wrench. I don`t have pics of the final work before painting, but I went back and filled some dimples and hollows with silver before sanding smooth. It does look better now.

rodar y rodar

The collets are really nice- we also have square and a hexagonal blocks for the same (5C) collets that work well for holding small parts in the mill, even useful for indexing bolt faces and such. But don`t be too envious, U! Remember that I`m doing all this stuff in my employer`s shop. My "home" shop is just a vise bolted to a hunk of I-beam under the carport or in the kitchen!

Almost done. The stem matched up nicely with the full sized drawing that I was working from, but before going any further, I threw it on the bike to compare position side by side with the adjustable stem I wanted to mimick, then mounted it and took it for a ride to be sure. The last step before sanding and painting was a decorative top cap. I brazed an internally threaded bushing into the top of the quill post to hole the cap in. Single pointed 3/4 UNF threads on the inside of the cap and screwed it into a srap piece to turn the top side. I`ve made these before with 303 and drilled a small ring of holes around the face to install and remove with a spanner wrench, (it looks supercool), but I keep losing the spanners, so this time I decided to just make it for an allen wrench. I also switched to aluminum because I don`t have any more stainless on hand. I have no idea how to broach a blind hole, so I just pressed the head of an allen bolt into a pocket on top of the cap, glued in with non-removeable Loctite. Should be plenty strong for the purpose. I hope.

Now that it`s all purdied up and mounted, I think I want to take a torch to it again. I changed my mind about mounting a small platform to teh canti bosses, now think I`ll install a few "water bottle" bosses in the stem and mount from those. Still need to ponder that possibility for a bit.

unterhausen

came out great, like the cap

calstar 

Thanks for showing the process, a lot of fun to follow it and the input generated by others was great as well. What do you think your total time was on the project? If/when you start another project please post it too.

Brian

rodar y rodar

Glad you liked it, Calstar. Time? Hmmm... to take a WAG, I`d have to say around 30 hours.