Custom Stem
 

I need a custom handlebar stem for our tandem.

Does anyone know of a good builder with a reasonable lead time?

What needs to be custom about it?

Length and angle.

People don't like making stems for some reason. Although Paul Brodie's video where he measures one he made may hold some clues. Never sell anything to a metrologist.

I have made exactly two tandem stems. The first one was made using a cut up frame for the part that attaches to the captain's seat post. I don't recall what I used to clamp the handlebar.

How much length and what angle of rise? Standard 28.6 steerer and 31.8 bar?

No, it's for a Santanna, so the steerer meeds to be 1.25" (31.8), about 130mm long with a 18º angle (roughly). Standard bar clamp. I can provide exact measurements.

You need a wedge style stem? You may end up having to go back to Santana.

It is threadless. I’ve exhausted all of Santana’s options.

A quick search around the web yields some 1-1/4 x 120-130mm stems, but 6 deg not 18. Can you use something like this and get your desired hand location using a riser bar of some sort?

I've never found such stems and I've looked extensively. Do you have a link?

A 130mm might work.

I'm not aware of a riser stem for a 1-1/4 steerer tube, and given the 400#(+) weight of the bike, I'm pretty sure I wouldn't want to use one.

The Zipp Service Course SL stem shows as available with a 1.25" steerer in various lengths including 130mm on the SRAM/Zipp web site. So far I've only found up 120mm for sale at typical online bike stores but I've only looked briefly.

Thanks!

I'm surprised I didn't find those, as I've done quite a bit of searching (the SRAM website has come up in other searches). What search query did you use?

Nothing fancy. I just Googled 1-1/4" stem 130mm and saw some mentions of the Zipp Service Course stem. Then I Googled Zipp Service Course to get to the product page I linked to.

I'm sure Dave Levy, TiCycles, could do it. Don't know lead times or cost. Probably not cheap but he could certainly build you exactly what you want.

He's building me a fork for the tandem and the due date is December/January. I'd love to have him do it, but I need it sooner.

Does anyone have any experience with Duane Draper @ Draper Cycles in Seattle?

Duane is a long time contributor here on BF. I can't remember any posts from him that made me shake my head:) I think he'll do you well. Andy

Great - thank you!

I follow Duane on Flickr, where I've seen in-process shots that show him to be careful and skilled. I've also been to his house and seen his work IRL. I would trust him to make a stem without any scary shortcuts taken.

He's not a full-time pro, he's got a day job, but sometimes a talented hobbyist can beat a full-time pro, by virtue of not needing to make everything profitable.

Thanks! So far, working with him has been great!

Hi all, I feel like I owe the group an update. First off, thanks Mike PromptCritical for your patience and thanks for the support from the group here.

Tonight I finished up the stem for Mike. It turned into a bit more of a project than expected but I'm really happy with where we ended up (aside from the 'reasonable timeline'!). I really enjoy taking on challenging projects like this.

After talking with Mike about his needs, we determined that the best way to approach this was an adjustable stem that I could send to him. He could ride around on it and find the right fit, lock it down and send it back to me. Then I can take measurements and make a real stem. I get the bonus of ending up with an adjustable stem for the future. I figured I'd do a quick drawing. This was an earlier version but you get the idea.


Since we wanted it to be adjustable, I didn't want to paint it. I wanted it to index so that when tightened the bars would be flat so I went with a square tube extension. I wanted it to slide nicely so I created brass shims to grip the extension inside a larger square tube clamp. I used stainless for all of the parts.


Getting the clamp square and brazed together so the binders were square and symmetrical, milling the brass shim and all the other steps to get the clamp completed went pretty well other than being time consuming. I used 50n silver fillet for this part.


I expected the extension part to be easy since it was really just a simplified standard stem. Some will be wondering about the propensity for stainless to stress crack when brazed. Yeah. I can confirm it does. I wanted the joint of steerer clamp and extension to be strong as the extension is quite long. At full extension it will exert some force on the clamp and joint. I used Nickel Silver and didn't consider the stress cracking until it was too late. I was using pretty thick-walled 0.125" square tubing and .065 stainless tubing for the clamp and the combination of heat required to heat the thick-walled extension and the copper-zinc filler just didn't work.

I had to call Mike and tell him that his 'reasonable timeline' was being extended. I offered him an option to cancel the project. He decided to proceed so I ordered 4130 square tubing and we agreed that I would gun blue the extension to protect the finish from rusting. Apparently due to weather that was delayed another few days.

The 4130 arrived Monday and I was able to get all of the fab work done Monday night and then some quick finish work and applying the bluing finish tonight.


I didn't spend as much time getting the fillets as smooth as I normally would since this will live a working life as a tool once Mike has returned it.


This is the start of the real stem made from the measurement of the adjustable stem.

Thanks Mike for your patience.
Duane

Beautiful work! Can't hardly wait to see it!

Nice work.
I wasn't previously aware of an issue with copper/nickel/zinc fillers and stainless. How did you notice it?

Thanks.

The clamp cracked almost immediately upon cooling. I had heard of someone having a hard time with KVA or 953 or some other stainless tubing and had the same problem - cracked when it cooled.

I had a few things working against me:

• I used pretty thick material for the extension since stainless is a bit weaker than 4130
  • It took more heat than stainless likes apparently to get filler to really soak into the joint
  • the flux didn't burn and it flowed fine and I got a nice inner fillet
  • there is a suggestion that even heating of the whole part might have prevented it.
• nickel silver melts a bit higher temp even than brass
  • After it happened, I read up a little and it mentions copper/zinc fillers don't get along with stainless. I assumed it was something about the filler getting into the grain structure of the stainless or something.
  • The more I read, I think they just take higher temps to melt and stainless doesn't like that; there are suggestions to anneal the tube before brazing but then strength goes way down so, I'm not sure if that's the solution.
• thermal expansion/contraction rates are different for the filler and stainless steel which adds stress
• The clamp had already been through one heat cycle to attach the bosses with 56%.

I think the combination caused the clamp part to crack. The clamp had already been through one heat cycle to attach the bosses with 56%. I think if I had just used Fillet Pro, It would have been fine.

I may see if I can make it work now that there isn't a time crunch. Having 2 extensions would be handy.

This is good intel. We don't know all the answers yet but these are clues. Thanks for sharing.

What flux did you use? So far I have only used it on lawn sculptures made from silverware, but the Cycle Design nickel silver flux made things so much easier. I will never use Type B on nickel silver again, unless it's after the zombie apocalypse and I need to make something to survive.