Rake adjustment

[Firstfour_imp]

You're saying decreasing rake angle (steering stem angle) increases trail. ......sure about that?

But perhaps you could show a scale diagram of what you're trying to accomplish. I've never seen a set of triple clamps where the yokes are set to angle the fork tubes more vertical than the stem, plus have a bigger offset to maintain the same trail. Is that what you're asking?

I don't get the purpose but I hope you find what you're looking for.

Sorry, I'm used to the coordinate system for the Patterson Control Model where the origin is located at the head tube intersection, and not the contact patch.

I want to decrease the rake as much as possible without the fender hitting the headers.

Sorry, what is the purpose of this?:huh:

 

[bubblerboy64_imp]

I think and I am sure I'll be corrected it not that by decreasing the rake the bike handles and turns in better. Think of the opposite and extreme the raked out chopper. Can you see getting one of those things around a tight turn?

Decreasing the rake on a CB1100? Unless you were going to run it on the track seems like the gain would be very minimal. And very expensive with a bunch of custom made parts.

 

[Dynaguy_imp]

Let's see, Honda's engineers spent who knows how many hours computer modeling this bike's geometry, then prototyping and road testing it and you can make it better by trial and error? WOW

 

[AzBob_imp]

You're saying decreasing rake angle (steering stem angle) increases trail. ......sure about that?

But perhaps you could show a scale diagram of what you're trying to accomplish. I've never seen a set of triple clamps where the yokes are set to angle the fork tubes more vertical than the stem, plus have a bigger offset to maintain the same trail. Is that what you're asking?

I don't get the purpose but I hope you find what you're looking for.

Sorry, I'm used to the coordinate system for the Patterson Control Model where the origin is located at the head tube intersection, and not the contact patch.

I want to decrease the rake as much as possible without the fender hitting the headers.

Sorry, what is the purpose of this?:huh:

Sorry, what is the purpose of this?:huh:
Turn-in will be quicker, however, straight-line stability will be lowered to a point where head-shake will likely occur.

My CBR1000RR's rake is 23.75 degrees and Honda purposely includes a (somewhat sophisticated) steering damper, stock. The CB1100's rake is already only 27 degrees, stock, and the front tire is a lot skinnier than my CBR's. Proceed with caution.

 

[Waffa_imp]

You're saying decreasing rake angle (steering stem angle) increases trail. ......sure about that?

But perhaps you could show a scale diagram of what you're trying to accomplish. I've never seen a set of triple clamps where the yokes are set to angle the fork tubes more vertical than the stem, plus have a bigger offset to maintain the same trail. Is that what you're asking?

I don't get the purpose but I hope you find what you're looking for.

Sorry, I'm used to the coordinate system for the Patterson Control Model where the origin is located at the head tube intersection, and not the contact patch.

I want to decrease the rake as much as possible without the fender hitting the headers.

Sorry, what is the purpose of this?:huh:

Sorry, what is the purpose of this?:huh:
Turn-in will be quicker, however, straight-line stability will be lowered to a point where head-shake will likely occur.

My CBR1000RR's rake is 23.75 degrees and Honda purposely includes a (somewhat sophisticated) steering damper, stock. The CB1100's rake is already only 27 degrees, stock, and the front tire is a lot skinnier than my CBR's. Proceed with caution.

Sorry, what is the purpose of this?:huh:
Turn-in will be quicker, however, straight-line stability will be lowered to a point where head-shake will likely occur.

My CBR1000RR's rake is 23.75 degrees and Honda purposely includes a (somewhat sophisticated) steering damper, stock. The CB1100's rake is already only 27 degrees, stock, and the front tire is a lot skinnier than my CBR's. Proceed with caution.
I'm doing it for an aggressive look more than anything. I'm a mechanical engineer with the software available to me to make intelligent guesses as to how modifications will result in reality. If I don't like it, it will be easy to make small adjustments.

I've been chasing/passing crotch rockets on 40 year old bikes, I'm used to a squirrelly ride.

 

[ChipBeck_imp]

I think Jim hit it right on the nose.

Trail is only affected by head tube angle and tire contact point. The only way trail would change from sliding the forks is from the change in center of gravity rotating the frame. I'm not sure how much this will change the trail, anyone tried it yet, notice any difference?

Waffa,

Sliding the fork tubes up in the triple clamp decreases trail and rake. That is a fact, not an opinion. The reason some people get confused about this is because they are considering rake in relation to the bike and it is not measured that way. Rake angle and trail are measured in relation to the ground on a flat level surface, not in relation to the bike. If you slid the forks far enough up in the triple clamp (assuming the frame or pipes didn't hit the ground first) rake would go to zero degrees and trail would decrease to zero and then go negative.

Then imagine going the other way with 5 foot long fork tubes. As you raised the triple clamps up on these tubes the rake angle would increase because it's measured in relation to the ground. And trail would increase tremendously.

Under normal braking as the fork tubes compress and forward weight shift unloads and raises the rear suspension the steering head angle in relation to the ground decreases and trail is momentarily decreased as well until the bike returned to its nutral state. Hope this helps.

Chip

 

[Jim21680_imp]

^I'm pretty sure he understands that, as we previously discussed the rotating frame concept. But to answer his original question...the only way to do this is fabricating a custom triple tree (and to over-engineer the hell out it, for safety's sake).

Searching for a one as a manufactured product is without doubt a wild goose chase.

 

[Deanohh_imp]

^I'm pretty sure he understands that, as we previously discussed the rotating frame concept. But to answer his original question...the only way to do this is fabricating a custom triple tree (and to over-engineer the hell out it, for safety's sake).

Searching for a one as a manufactured product is without doubt a wild goose chase.

Forget about rotating centers of gravity (can a point in space rotate?), Patterson computer models, moments, dynamics, and everything else. We can't even get even a simple illustration drawn on paper with a simple diagram. This would at least show what this monster would look like and perhaps show if the geometry in question is possible. Valid comments are ignored and its the same thing repeated page after page. The whole concept is bogus and this thread is going nowhere.

 

[Guth_imp]

^I'm pretty sure he understands that, as we previously discussed the rotating frame concept. But to answer his original question...the only way to do this is fabricating a custom triple tree (and to over-engineer the hell out it, for safety's sake).

Searching for a one as a manufactured product is without doubt a wild goose chase.

Forget about rotating centers of gravity (can a point in space rotate?), Patterson computer models, moments, dynamics, and everything else. We can't even get even a simple illustration drawn on paper with a simple diagram. This would at least show what this monster would look like and perhaps show if the geometry in question is possible. Valid comments are ignored and its the same thing repeated page after page. The whole concept is bogus and this thread is going nowhere.

Deanohh, if this is really bothering you, the simplest solution would be to step out of the thread. Intermixed in all of the posts is a fair amount of interesting information. People can choose to do with it what they wish.

The thing that I would wonder about the proposed triple clamp system is the impact on geometry when the bars are turned. As the fork tubes would no longer be rotating parallel to the head tube, the tire's point of contact would be thrown off-center whenever the bars aren't pointed exactly straight.

In other words, with the bars straight, the front wheel is pulled back X inches. When turned, the front wheel is going to shift to the left or the right by some percentage of X, which isn't the case when the fork tubes are parallel to the head tube. Or so I think anyway.

Guth

 

[Lord Popgun]

Man,

That was like reading hockey rules in MAD magazine back in the day!