MuchAlohaNui
Senior Retro Guru
Maybe @RockiMtn can confirm (if he wants of course). He's got an old Rocky Mountain Ti.
Preview! Preorders!! Redesign Rocky Mountain tilted seat clamp.
- Thread starter Fatboy1974
- Start date
NigelFinnighan
Rocky Mountain Fan
both my aluminum frames are 31.8 od seat tube. Vertex and Thin Air. I can't help with a Ti-bolt.
Shenlong
Dirt Disciple
Seat clamps with built-in threads are a flawed design. They all suffer from the bolt bending under torque a.k.a. Banana Bolt Syndrome. Not good.
Single-pivoting barrel nut seatclamps like the Salsa Lip-Lock are kinder on your frame's seat tube slit and also better for dropper posts than the above. However...
The absolute best seat clamp design on the market right now is the Pembree DBN. Dual-pivoting barrel nuts completely outclass even the single-pivoting barrel nut types like the Salsa.
https://pembree.com/dbn-seat-post-clamp/
Single-pivoting barrel nut seatclamps like the Salsa Lip-Lock are kinder on your frame's seat tube slit and also better for dropper posts than the above. However...
The absolute best seat clamp design on the market right now is the Pembree DBN. Dual-pivoting barrel nuts completely outclass even the single-pivoting barrel nut types like the Salsa.
https://pembree.com/dbn-seat-post-clamp/
Attachments
I agree. Barrel nuts help a lot distributing tensions. But again we're in front of a design we want to keep original because of its retrobike value.
I did around 13 years ago, a very light seat clamp with similar design. It was ridiculously light.
In this tilted retrodesign, I let some margin to bolt head housing and 7mm hole, to allow the bolt M6 some movement when it's starting to be misalingned. But you are right, right way would be with barrel nuts.
This is what I'm going to produce. Very close to original with some improvement ( 3 mm widder in height to better brace the ST).
M6x20 Ti bolt. Please, If anybody has some doubt or find some mistake. will be appreciatted.
I still do a small step that can be easily removed. It doesnt ad complexity at CNC because it's flat, not tilted machining, and you have a reference when installing.
Edited: I deleted the files. I need to protect a little my Intelectual property.
30.0 mm ID unit and 31.8 mm ID unit.
M6x20 Ti bolt. Please, If anybody has some doubt or find some mistake. will be appreciatted.
I still do a small step that can be easily removed. It doesnt ad complexity at CNC because it's flat, not tilted machining, and you have a reference when installing.
Edited: I deleted the files. I need to protect a little my Intelectual property.
30.0 mm ID unit and 31.8 mm ID unit.
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MuchAlohaNui
Senior Retro Guru
Stupid somewhat rhetorical, long-winded question: With any clamp, do you want the primary clamping force along the center line if the circumference of the clamp body, tangential and equal at all points along the inner surface? Seems to get past this the clamp would need more material overall with a higher torque rating.
Using the center axis of the tightening bolt (as the bolt is the means of providing the primary force), this then reduces the mechanical ability of the clamp to properly and uniformly pinch the seat tube to the seat post. Like you have a mechanism that utilizes static friction but due to the shape of the clamp and how much clamp is below the clamping bolt, a loss in static friction is realized because the bolt wants to sort of pull the material of the clamp upwards.
I am open to corrections of my limited physics background.
Interesting project.
Using the center axis of the tightening bolt (as the bolt is the means of providing the primary force), this then reduces the mechanical ability of the clamp to properly and uniformly pinch the seat tube to the seat post. Like you have a mechanism that utilizes static friction but due to the shape of the clamp and how much clamp is below the clamping bolt, a loss in static friction is realized because the bolt wants to sort of pull the material of the clamp upwards.
I am open to corrections of my limited physics background.
Interesting project.
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In my opinion, here pressure can not be equal in all surface because of tilted design. If it was equal, it would appear a force (torque) trying to rotate the clamp in XY plane, so I assume that most of pressure appears at both sides of the clamp, and pressure on front and rear is compensated with friction of both sides of the clamp with Seat tube to compensate the torque generated for not selfcompensated front/rear pressure.
In an ideal world, seat clamp should work like a "belt", but belt needs traction forces. Because it is tilted, then we need to create a compensation torque. The wider the cilindric area, the less pressure needed in front/rear.
But system can work.
Some Rocky mountain guru can give me light about colors needed in RM series 1993 to 1995 tilted clamps?
Gold
Black
Silver
Red
Others?
Gold
Black
Silver
Red
Others?
Ok. Clear for me. I'm ord3ring tomorrow the following:
20 units 30 ID:
20 units 31.8 ID:
Preorders:
@aparittion_cycles: 2 units gold 30mm
@IHseeker : 3 gold and 3 black 31,8mm
@jonnymcenroe 1gold 30 mm
At the end I'm ordering with Ti bolt ( I meant the hardware, not the Ti Bolt frame ;-) )
Prices I expect lower than 25€+shipping each, If no custom charges.
20 units 30 ID:
20 units 31.8 ID:
Preorders:
@aparittion_cycles: 2 units gold 30mm
@IHseeker : 3 gold and 3 black 31,8mm
@jonnymcenroe 1gold 30 mm
At the end I'm ordering with Ti bolt ( I meant the hardware, not the Ti Bolt frame ;-) )
Prices I expect lower than 25€+shipping each, If no custom charges.
