Re: flexible rubbery bits as part of the frame;
Flexible mounting of the steering head.

A simpler method is to use castable urethane, cast in-place.
Mating parts to have ribs to engage the bulk of the flexible material, and help
reinforce against shear loading.
Incidental advantage: bearing recesses can be remachined in a smaller, easily held component.
Features desired: Unboltable steering head assembly or outer shroud.
This makes any mods,rework easier.
Problems: Locating a Finite Element methodology and software in a "ready to run" package
On Google, there are some articles that look like University papers, but it is not really "off-the-shelf".
The setup is too complicated for "hand-type" approximation.
Deflection should be naturally self limiting, but my initial suggestion is 50kgf to 1cm sideways displacement at the lower wheel rim,
estimated lever arm 800 + 300 = 1.1 m
I need to check fore and aft motion under braking as well. Most force aligns along the fork tubes at
say 30 degrees rake, so the bending moment is not that huge. Possible aggravation of brake chatter?
Inherent damping counters chatter.

Elements like this could be added to a swingarm stiffener as well.

Question: would an average street rider notice any difference if a bike was fitted with these elastic bits?
The inherent "rubber damping" should reduce any possible oscillations, but so does "moderate" rake/trail
and a good set of tires. They have sidewall and tread damping on the road surface.

 

Re: flexible rubbery bits as part of the frame;
Flexible mounting of the steering head.

A simpler method is to use castable urethane, cast in-place.
Mating parts to have ribs to engage the bulk of the flexible material, and help
reinforce against shear loading.
Incidental advantage: bearing recesses can be remachined in a smaller, easily held component.
Features desired: Unboltable steering head assembly or outer shroud.
This makes any mods,rework easier.
Problems: Locating a Finite Element methodology and software in a "ready to run" package
On Google, there are some articles that look like University papers, but it is not really "off-the-shelf".
The setup is too complicated for "hand-type" approximation.
Deflection should be naturally self limiting, but my initial suggestion is 50kgf to 1cm sideways displacement at the lower wheel rim,
estimated lever arm 800 + 300 = 1.1 m
I need to check fore and aft motion under braking as well. Most force aligns along the fork tubes at
say 30 degrees rake, so the bending moment is not that huge. Possible aggravation of brake chatter?
Inherent damping counters chatter.

Elements like this could be added to a swingarm stiffener as well.

Question: would an average street rider notice any difference if a bike was fitted with these elastic bits?
The inherent "rubber damping" should reduce any possible oscillations, but so does "moderate" rake/trail
and a good set of tires. They have sidewall and tread damping on the road surface.

Typically, elastomers are springs. Pure springs are not good at controlling vibrations. Actually, springs can lead to oscillations and multiple springs in a system can cause resonances that can reach amplitudes that were never realized on hard-mounted systems.

To control vibration, including suspension components, is a dampened spring. Oil adds friction, some (few) foams are energy absorbing, and as the patents quickly tumble, magneto-rheological fluid systems can dampen the oscillating mass.

Your question was not perfectly clear but... best I could do.

 

Typically, elastomers are springs. Pure springs are not good at controlling vibrations. Actually, springs can lead to oscillations and multiple springs in a system can cause resonances that can reach amplitudes that were never realized on hard-mounted systems.

To control vibration, including suspension components, is a dampened spring. Oil adds friction, some (few) foams are energy absorbing, and as the patents quickly tumble, magneto-theological fluid systems can dampen the oscillating mass.

Your question was not perfectly clear but... best I could do.

O: Even if I don't want those particular rubbery joints, It strikes me as a useful skill to learn.
FreeByte has a good article on "free" FIA (finite element analysis). I haven't read it yet.

There is a certain amount of hysteresis in urethane that a steel spring does not have. If you really wanted to, you could calculate damping and natural frequencies.

You could also create quite a complex joint, with rotation, translation(sideways),and greater stiffness in one plane than another. For instance, I would want good sideways rotation, and stiffer front-back rotation,
for braking loads.
I think it is rheological, not theological. -that is for adaptable damping-too expensive for me!

Looking at the front of a rubber mount twin cylinder bike like a Norton Commando shows that
it is not as simple as it looks. -large amplitudes at low revs. They smooth out once you get going, though.

 

The theory is called Hyperelasticicity,
and is a horrible mess of Tensor stuff and partial differentials-above my "pay grade".
I need something already set up that can be plugged in to an FEA package by mere mortals.
there are a number of FEA packages: I suppose I need to learn some computerised draughting (CAD)??
http://www.calculix.de/
http://lisafea.com/

http://www.freebyte.com/cad/fea.htm

 

Again you go where real engineers have feared to tread. For good reason in motorcycle design. I can't even imagine how a bike with a rubber mounted steering head would go down the road. The normal way of bike handling is to stiffen the steering not loosen it. Don't even know where you come up with these ideas, but when and if you put them to use, you're looking at winning the Darwin Award for bike design.

They use some urethane bushings in some rear swing arms and some handle bar mounts, to absorb vibration. Car suspensions use it for the same reason plus sound deadening from the road, but a motorcycle steering head? I'm beginning to wonder if you've ever rode a motorcycle?

 

Again you go where real engineers have feared to tread. For good reason in motorcycle design. I can't even imagine how a bike with a rubber mounted steering head would go down the road. The normal way of bike handling is to stiffen the steering not loosen it. Don't even know where you come up with these ideas, but when and if you put them to use, you're looking at winning the Darwin Award for bike design.
/*
O: controlled rubberiness is not much of a problem. You have to know what you are getting into, and set some load/deflection limits. At the worst, it will slow down responsiveness, make the steering feel a bit vague,
or create an uncomfortable vibration resonance frequency. I can test for these, and adjust them out.

I don't think this stuff is really worth doing for a non-race bike. Maybe a factory race team might do something like this, with expert riders.
*/
They use some urethane bushings in some rear swing arms and some handle bar mounts, to absorb vibration. Car suspensions use it for the same reason plus sound deadening from the road, but a motorcycle steering head? I'm beginning to wonder if you've ever rode a motorcycle?

O: I think 2010 was the last time a road a motorcycle.?? I don't use severe control inputs or lean way over-
don't like the look of a rather abrasive road rushing under my elbow! Longer side fairings under the handlebars
may be more suitable to me. I want to give it another go. I think I have another 15 or so motorcycling years left in me yet.

 

I think I have another 15 or so motorcycling years left in me yet.

Not if you implement some of your ideas on a real bike.

 

Not if you implement some of your ideas on a real bike.

It is not that unsafe. LVVTA wouldn't let me do it if it was likely to cause a road hazard.

For instance, if I wanted to make a detachable steering head, I would have to prove via calculation logbooks
that it would withstand at least 5 Gs of loading for all the expected cases. To do that would likely take
more that 4 lots of 10mm bolts, plus lug plates and brackets suitable for right angle loads. if the base plate was
1.5 mm, full strapping would likely be needed to distribute bolt loading. A possible bolt scheme would be two
bottom; two each side; in a triangle formation. The metal shroud is the final arbiter on maximum displacement,
but sandwiched urethane material would limit shock loading.
I can test for dynamic instability in a safe environment before submitting the vehicle for a full road test.
A similar argument goes for any controversial design features.

 

Your correct @shortbus I was headed up the Canyon last week, doing 75 on Concrete Freeway, in the turns the bike became Resonant Freq, depending on the speed and to add more motion to that would decrease my ability to control the bike. Springer Seat and 2 custom rear shocks with overflow cylinders kept me on the road. Forks are standard equipment.

Otherwise custom from the top down.

kv

 

Your correct @shortbus I was headed up the Canyon last week, doing 75 on Concrete Freeway, in the turns the bike became Resonant Freq,
kv

O: motorcycles are capable of unstable periods depending on tires, loading, equipment. Even if they are factory tested, if anything changes, you could have problems. For instance, doing Bonneville Salt speed runs on a standard motorbike is just asking for trouble. They are not designed or intended to run on that surface.

You take a bit of a risk if you build a bike from scratch, than it will have some sort of weave instability.
Steering dampers help in some cases, as do having fairly "sticky" tires. Usually you can get out of the
"weave zone" before being thown off, or the weave damps itself out. Some redesign/rebuilding may be required.
I have heard that some models of the Yamaha RZ350 had chronic weave instabilities at speed that were
hard to get rid of.

 

O: motorcycles are capable of unstable periods depending on tires, loading, equipment. Even if they are factory tested, if anything changes, you could have problems. For instance, doing Bonneville Salt speed runs on a standard motorbike is just asking for trouble. They are not designed or intended to run on that surface.

You take a bit of a risk if you build a bike from scratch, than it will have some sort of weave instability.
Steering dampers help in some cases, as do having fairly "sticky" tires. Usually you can get out of the
"weave zone" before being thown off, or the weave damps itself out. Some redesign/rebuilding may be required.
I have heard that some models of the Yamaha RZ350 had chronic weave instabilities at speed that were
hard to get rid of.

Almost all "weave" issues are related to poor weight distribution or even aerodynamics that cause lift on the front of the bike (directly or indirectly). Evkdence is tbat shifting body weight forward normally corrects the issue.
Whether the RZ350 or ST1300 Police edition - it works.

 

Almost all "weave" issues are related to poor weight distribution or even aerodynamics that cause lift on the front of the bike (directly or indirectly). Evidence is tbat shifting body weight forward normally corrects the issue.
Whether the RZ350 or ST1300 Police edition - it works.

O: I had a case that was not related to moving weight forward.
It only happened while leaded over at speed, and was cured by replacing a cheap Chen Shing rear tire
with a Metzler. The Metzler seemed to have a more "sticky/higher hysteresis tread compound.
Many bikes need a steering damper to get rid of a continuous low level steering shimmy. It can help
with sudden "Head Shake" as well-presumably while you are playing "Demon Racer"
I heard about the ST1300 police problems-cured by actually following factory conversion recommendations!
presumably centering equipment weight and getting it further forward.
Steering-head mounted fairings can cause problems, too. I think one of the RZs had a bikini fairing.
Went much better when you turfed that.
There may be many cases where forward weight transfer will help, but likely
not in all cases. Tony Foale may have some further info/opinions there.

 

When I ride my only concern is that the bike "feels right" and after many years of placing my butt on a bike I have come to know what I expect for feel and handling. When the bike feels right I just enjoy the ride. When something just doesn't feel right I address it, for example the air pressure in my shocks. I can tell if they need air in how the bike handles. The same is true for tire pressures. Currently at 67 going on 68 in February I have no plans to stop riding and began riding back when I was around 19 or so. Anyway with the possible exception of doing a few lighting modifications I am quite content with the bike "factory" so I leave things like the frame alone.

My only steering head mount fairing was back around 75 on a Honda 550 four. It never really produced any problems that I recall. Thinking back that was the only fork mount fairing I ever had, that I can recall anyway. It was never a problem and really didn't interfere with anything.

All of my bikes have been what I call a "Road Bike" as my days for playing motocross ended years ago and I am not the "crotch rocket" type. I recently rode a little Honda Rebel 300 and I had a great time on that little bike. Enough fun that I would consider one for riding around locally. I guess they make a 300 and 500 model and the little 300 I drove was just fine.Real tempted to find a used one.

Back on topic I seldom have any desire to change anything, with the exception of lighting, from factory. When I have looked to get another bike I ride it and if it responds well and simply feels right I consider it.

Ron

 

@ Reloadron, GopherT, [URL='https://forum.allaboutcircuits.com/members/killivolt.71750/']killivolt You guy's haven't been following this guy's threads, I don't think. He is really a troll and trying to get his name out into the 'net' to increase hits to his blog. At his blog he claims to be a motorcycle design engineer. I've been reading his threads since he came here, and one thing he isn't is any kind of mechanical engineer. He makes up his own formulas that have no real meaning in the context of mechanics. Using his own 'terms' for the formulas. He has no understanding of how even the simplest mechanical elements or machines work.[/URL]
https://forum.allaboutcircuits.com/members/gophert.185531/
I'm pretty sure that when he saw links to AAC, he thought it was really called "All About Cycles". By his own admission he has been practically run off of the motorcycle forums. For his outlandish ideas about how things work and his refusal to accept help in trying to change his thinking. I've tried but instead of giving up, I continue to try to get through to him.

 

@ Owen Nieuwenhuyse What exactly does your use of the bits," O:" mean in each of your replies? Just asking because I've never seen anybody use them in their replies but you. It must mean something, care to share?

 

I'm pretty sure that when he saw links to AAC, he thought it was really called "All About Cycles". By his own admission he has been practically run off of the motorcycle forums. For his outlandish ideas about how things work and his refusal to accept help in trying to change his thinking. I've tried but instead of giving up, I continue to try to get through to him.

I have followed his post and some bizarre ideas to apply to motorcycles. I even commented in one of his threads. Today my underlying message was if something works, don't screw with it. Now if you will excuse me I need to get back to installing training wheels on my motorcycle.

Hey, if we get together for dinner at Cracker Barrel again while the weather is nice I'll ride the bike. Last time I drove home in snow.

Ron

 

Last time I drove home in snow.

You had a car? I walked.

 

You had a car? I walked.

We can't all live right around the corner. Maybe one day lunch?

Ron

 

I've been reading his threads since he came here, and one thing he isn't is any kind of mechanical engineer. He makes up his own formulas that have no real meaning in the context of mechanics. Using his own 'terms' for the formulas. He has no understanding of how even the simplest mechanical elements or machines work.

It's why I dropped out of that other thread early on.

There's nothing gainful to be had from discussing a topic with someone who shows they clearly have no real rational applied knowledge and understandings of and with it.

 

There's nothing gainful to be had from discussing a topic with someone who shows they clearly have no real rational applied knowledge and understandings of and with it.

So if I once sat on a motorcycle or had my picture taken standing beside one do I qualify as having rational applied knowledge and understanding? I also once sniffed motorcycle exhaust if that helps?

Ron