crank help?

[ReklinedRider]

Maybe (very likely!) I'm confused.....instead of cutting the boom couldn't you drill out the water bottle mount thingys on the slider and have more room to insert the boom into the slider?

I'm calling the 'boom' the smaller diameter tubing with the curved end that has the bottom bracket shell, and I'm calling the 'slider' the larger diameter piece that the handlebar mounts to. Or is that backwards? Maybe the terminology confusion is due to what i call the boom having the larger diameter on the Old Yeller versions, while on Big Red and V20 the boom has the smaller diameter? What is the correct terminology, so we're all on the same page?

It seems like the slider on the Yellers got stuck down inside the boom on one bike when it got jammed into the boom and impinged on the curve at the BB end.....hermetically sealed as Larry said. On the V20 that can't happen. I hope.

If I went to cranks even 2cm longer, I'd have to either cut the boom or drill those slider(?) cage mounts out. Sticking with 145mm for now!

 

[RAR]

Those cage mounts are just "Rivnuts". An aluminum rivet that has threads inside...easy to drill out easy to replace if you know of someone who has a Rivnut kit. If you use the mount for a water bottle then you need to cut the boom...or you could put a slot in it to clear the Rivnuts but that is a bit more difficult.
You could also drill out the Rivnuts and use this. http://www.twofish.biz/bike.html

 

[ReklinedRider]

Hmm Hardy just curious, what is your boom/slider combined length ('A' in the above diagram posted by Ratz)? I doubt i'm any taller than you, 5'6" w 41.5" ex-seam.

I just went out and measured my 'A' length and it's 33in or 83.82cm. The reason for that length is that's as short as I could make it without either cutting the boom or drilling out the cage mounts. By the book, my 'A' length should be 75cm. But with it at ~84cm, i'm happy w the BB height and arm position.

Measuring knee clearance now, if i somehow made the A length 9cm shorter i would have no knee clearance at all--and my notch would be set at 4.5! I do recall now that when i used that formula to assemble the Sivio 1.5 i had no knee clearance, and had to just set my arms where i liked, then let the boom out to accommodate leg length. That's why i ignored that formula this time round and just got lucky on fit......I think!

It seems also (but i sure could be wrong) that making A that short would mean having to push the boom assembly and handlebars further out to accommodate leg length, but the end result would still be approx the same BB height. The bars would just be further out and higher up, and then i couldn't see anything of the road ahead! Maybe I should drill the cage mounts out and start over. Hey Larry i may need that recurved slider back (just kidding keep it as long as you like)

 

[ReklinedRider]

Those cage mounts are just "Rivnuts". An aluminum rivet that has threads inside...easy to drill out easy to replace if you know of someone who has a Rivnut kit. If you use the mount for a water bottle then you need to cut the boom...or you could put a slot in it to clear the Rivnuts but that is a bit more difficult.
You could also drill out the Rivnuts and use this. http://www.twofish.biz/bike.html

RAR, What size bit to drill them out?

 

[RAR]

Reklinedrider, I'm not knowing the exact size, use a bit that is a size or two bigger than the bolt. I would start small and go up one size at a time until it comes out or loose, then pull it out with pliers. That way the hole is not bigger and you can put a new Rivnut back in if necessary.

 

[ratz]

What is the correct terminology, so we're all on the same page?

Boom has the BB
Slider has the handlebar

I just went out and measured my 'A' length and it's 33in or 83.82cm. The reason for that length is that's as short as I could make it without either cutting the boom or drilling out the cage mounts. By the book, my 'A' length should be 75cm. But with it at ~84cm, i'm happy w the BB height and arm position.

Kline that's what I would expect from your photos. I'm 5'9" but my x-seam is only 42". That ratio of Xseam to height will control how far back your entire boom is. There's no way I can fit on the bike without a cut down my arms would be too far back for comfort. I'm guessing your handlebars are roughly 4cm further back than mine (½ the different in our heights) which pulls your BB closer and higher. If I had that 4cm I would JUST fit; I choose to cut off the extra because it gives me adjustments in both directions.

Also Shoe and cleat selection will also affect this. A Look cleat has a lot more reach than an SPD, Frog, or Zero. Each is unique

Without cutting the boom the furthest I could push it in was to about mark 17. Right now they are loosely set at 12.5.

It's always interest the Boom Length for Mrs Ratz is within 1cm of mine. I can't ride her bike and she can't ride mine. Even though I'm only 2.5 inches taller than her (if she's kind and doesn't wear heels). She's all leg but can't reach my pedals, and my sternum is in her handle bars and knees feels way to far back on her bike.

Little measure big differences. That's why if you start moving the boom out or tweaking always do it 1cm at a time at most.

Those cage mounts are just "Rivnuts". An aluminum rivet that has threads inside...easy to drill out easy to replace if you know of someone who has a Rivnut kit. If you use the mount for a water bottle then you need to cut the boom...or you could put a slot in it to clear the Rivnuts but that is a bit more difficult.
You could also drill out the Rivnuts and use this. http://www.twofish.biz/bike.html

Another trick is drill them out; get you boom perfect; then dill into the old hole and through the inner boom. The install the Rivnuts and the boom is now locked into the perfect length.

 

[ReklinedRider]

Boom has the BB
Slider has the handlebar

Makes sense to me.

I'm 5'9" but my x-seam is only 42". That ratio of Xseam to height will control how far back your entire boom is.

Also, means w a short torso like mine, the neck rest is guaranteed to be a challenge. Have some ideas; waiting on materials.

Little measure big differences. That's why if you start moving the boom out or tweaking always do it 1cm at a time at most.

Another trick is drill them out; get you boom perfect; then dill into the old hole and through the inner boom. The install the Rivnuts and the boom is now locked into the perfect length.

No tweaking for awhile yet! Let alone locking anything in.

 

[Robert O]

Makes sense to me.



Also, means w a short torso like mine, the neck rest is guaranteed to be a challenge. Have some ideas; waiting on materials.



No tweaking for awhile yet! Let alone locking anything in.

"Have some ideas; waiting on materials". Darn it, don't you know I'll be laying awake nights waiting for this reveal! ;-)

 

[ReklinedRider]

No use losing sleep over something that or may not work! Anything I come up with will be strictly 'Amateur Hour'

 

[Robert O]

No use losing sleep over something that or may not work! Anything I come up with will be strictly 'Amateur Hour'

I've got faith!

 

[ReklinedRider]

I hope you have patience as well!

 

[justbob20]

Update; drilled rivnuts out, thought it would be better to turn bike over for this and yes remnants fell into boom/slider, so handlebars removed, bike tilted and viola. Initially in an effort to ? improve drag, I had hoods to far forward causing leg clearance issues. So back into the garage for adjustments pulling hoods into upright position. I feel more power in the forward stroke, but still may be overflexed with knee angle. I was able to increase max speed on a flat stretch that I do routinely from 33.4 to 34.7 with moderate head wind. I still feel that shorter cranks may be in order to fine tune lengths, but for now Im going to let it ride. Hope to post some pics soon for guru scrutiny. I love this forum! I can always count on good input to help a newbie out, thanks guys !

 

[justbob20]

Here I sit... 165 arms

 

[ratz]

Immediate reaction that a pretty good fit with 165mm cranks.

Adjustments you could play with.

1. Move the head rest out a bit;
2. Slide butt forward on the seat that will tip your head forward a bit and get you looking down the road
3. leave handle bars at that placement so you pick up a little more relaxed arm position.
4. Lengthen the boom a bit to compensate for sliding forward.

Here's old'e yellow with 165mm cranks under power; nature ankling (heel coming further back that you can get stationary) is going to keep the knee slightly less bent.

 

[justbob20]

Ratz, I see what you mean and will try your suggestions, the pic shows what you are trying to depict. Time to adjust, ride and see, thanks again for your time and consideration

 

[justbob20]

almost there me thinks. As Ratz reported knee flexion angle less acute when riding verses stationary, also harder to show true riding position in stationary photo. Lastl, I noticed tighter turning radius with butt more forward. Next adjustment will be head rest padding. Thoughts?