Topic: Intresting front end concept

[Shenanigans]

What do yo guys think?

[Terry in Australia]

The pivot angles are all wrong.

[KB02]

So, does the part on the upper fork slide up and down?

[Markcb750]

I assume you are trying to reduce the brake induced bending moment from the forks, the green arrow in the second diagram is a little confusing.


Assuming this is your objective, and that the brake mounting arm and upper slide travels with the lower fork...


The up and down motion of the wheel will cause what looks like a guide sleeve in the triple cramp area to do two things.

Limit the location of the upper or lower triple clamp

Add considerable "upsprung" weight and friction to the front suspension

Make a free body diagram of the wheel in its forks, note the force of the brake and the moment on the wheel axle from stopping.  this design would reduce the deflection (bending) of the fork into an "S" shape, but this can be addressed by stiffening the fork in the plane of the braking moment. 

I have seen Buel use this type of rim mounted rotor, and it definitely has a potential to bend the front forks greater then a hub mounted rotor,  It sure looks sweet though.


"ADD..Mark D. Veety ASU BSME 1981...

[Shenanigans]

I think the point of it was basically to reduce front end dive under hard braking using the brake assembly being on a pivot. The "guide sleeve" is actually attached to the upper fork and the resistance in the brakes pushes the forks apart.

[Markcb750]

I don't see the "pushing forks apart reaction" yet, maybe your could tell me a little more or give us a front view of the concept.

A lot of movements going on when road undulations, fork reaction (longitudinal movement), and your brake reaction causing the pivot bracket to change radial distance of the brake pads.

I think there are systems which restrict fluid flow in the shock in response to brake fluid pressure, zero unsprung weight to negatively impact suspension performance.


I guess that is why I thought you where trying to reduce fork bending, not reducing front end dive.  Sorry.


What is the temperature in AZ today?

[Shenanigans]

I just realized how inept my description is. Maybe this will help, this is what happens under braking.




It uses the resistance of the caliper to decompress the fork.

Why cant I think of a simple way to describe it haha.. my brain is not functioning today.

[Markcb750]

I understood it with out that.

What I am trying to say is when you applied the brake, the forces would want to move  what I am calling the "slider" up (toward 1:00 if that helps).

If the slider does not have freedom to move, your suspension will not work at all...as it is drawn I think you need one more pivot point to allow any travel in the fork because again the slider will need to maintain its alignment to the fork centerline as it moves.

Thats why you need to give the front view, maybe there is something there that I am not seeing.

[Shenanigans]

What is the temperature in AZ today?

I could not tell you as I am not in Az right now.

I think I get what you guys are saying as it would be very hard to get "balanced" in the right spot to make it usefull.

Heres the other picture I had one it.

[Markcb750]

Great 3D design work.  What software is it?

It was still 100 last week in Phoenix according to a friend out there.  Damn almost October.

Like fishhead said...

I recommend you look into some new  antidive stuff see if you can talk the parts guy at a BMW dealer to discuss the antidive parts on a new RS...Better then mechanical compensation, No impact on suspension response when brakes are not applied.

[754]

Is that from van der Quak's site?

A guy here in town designed his own front end, looks a lot like an old girder, but has a hidden shock inside the steering neck which is a bit oversize. It works well, even at speed and he tested it to 160 mph.

 It is not antidive but runs what appears to be a large drum brake with discs hidden inside..

[Shenanigans]

Great 3D design work.  What software is it?

I am not sure, just to make it clear its NOT mine, I came across it and saved the images and lost the source. I am pretty sure it was from hellforleather?

I have a buddie who's dad has an BMW ST1100 That is kind of similar to what you described 754. One shock in the neck similar to a girder but it still had normal looking forks, but I would assume that the forks were only for absorbing load or whatever and the shock has damping and separated it from the fork. I guess lately I have been just trying to understand diffrent suspension concepts (might as well make my idle time here useful )because it seems that even the top of the line stuff now has its limits. If any one has any good reading on this kind of stuff, it would be appreciated.
Maybe when I get a chance back home I will poke around the dealership and look at those kinds of suspension and I can oggle of a speed triple while I am there...

100 in Phoenix? Man, its finally starting to cool off...

[Markcb750]

Email last night said temps in Phoenix down in the 90s!


You forced me to think about the dive problem a little, I think  with just a small brake caliper and a linear steel plate connected across the fork seal line I could slow/stop dive.  would take some good guesses as far as piston ratios and prevention of front brake performance degradation...

Would be interesting to apply on one of the new "upside down" fork sets as caliper could be on the stationary side of fork, hydraulic connection just a "T" in the brake line...

I am halfway through a dual brake setup for my '76. looking for the right calipers to incorporate, want something different then stock. Way too much stuff on the net to look at.  So I stopped designing and committed to just restoring.  Maybe on the next one (an "F") and I'll look at an antidive.

[754]

Try machining speedo side so that the speedo drive gutz fit into the brake bracket.

As long as the bike has a tach, why worry about speedo! Or run a bicycle electronic unit on rear wheel.

[Raul CB750K1]

The anti-dive fork was invented years ago.


It is called Earles fork. Widely used in many BMW models on the fifties.

From wikipedia



The Earles fork[4] was a variety of leading link fork where the pivot point was aft of the rear of the front wheel ─ this was the basis of the Earle's patent. Designed by Englishman Ernest Earles, this triangulated fork actually caused the front end of a motorcycle to rise when braking hard — the reverse of the action of a telescopic fork. It was designed to accommodate sidecars, and from 1955 to 1969, BMW used the fork even though most of its motorcycles were sold as solo bikes.

[754]

Easier to leave the whole thing alone..












Just buy a complete anti-dive fork..matching guages is the least of the problem ..

[crazypj]

I don't think the Earles fork was ever designed to have an anti-dive feature.
 The reason it 'lifts' front end is the brake stay/torque arm is mounted to the actual suspension arm so torque reaction lifts front end when braking.(as on Honda 50's ec with link suspension) there are loads of designs for mechanical anti-dive if you do some research, it was the 'big thing' in the early/mid 1970's for GP bikes.
 Tony Foal did a lot of work on 'everything' motorcycle, has a lot of material on net and a couple of books
http://www.tonyfoale.com/Articles/index.htm
PJ