Steering and Handling Discussion.

[bradley300]

3 months how bout a new question? just for discussion, it doesnt effect me at all.

How does frame size effect the optimum width of a quad? Lets compare a 450r and a Cobra 70.

Compared to a Cobra, the 450r is a huge machine and 50 inches is considered the best width (considering no restrictions such as trees where beeing narrow would be better). Now, with a Cobra Being so much smaller, is 50 inches still the premium width, or is the preimium width for a race quad change to match the size proportions of the rest of the quad?

[IMSROLL450R]

I would think the width of the quad would need to be determined by the height and weight of the quad with the rider on it. A smaller, lower quad with a smaller rider wouldn't necessarily need to be 50 inches. That may be too wide and a narrower width may achieve the same cornering characteristics yet be easier to navigate through tight areas.

[400exrider707]

Finally some new material!

I agree with the above post, although I would add that where you are riding will determine this as well.

However a narrower frame with longer arms will reduce change in track width, though you could design a frame and arm combination to almost eliminate this.

You wouldn't want the quad to be 50" wide and only 40" long, you would want the width to be proportional to the length of the quad. On the Honda for instance.... Look at the front spindles when the handlebars are pointed straight. Draw imaginary lines from the angled sections (where the tie rod ends mount) towards the back. Where those two imaginary lines meet, should be the center of the axle. This is something I've never tried to really verify, but I have read about it before.

I'm interested to see the facts behind this, because it is something I'm not too familiar with...

[TNT]

Finally read through all that and it made my head hurt…..lol! I'm a 25 yr Aircraft Design Engineer and think in way more detail than this and design products in the $750,000,000 dollar range, not $15, 000. I found the material 400EXRider707 presented for the most part very well thought out…….I can tell you have a good mechanical aptitude and can visualize geometry well. I do that all day with very sophisticated computer graphic's, CATIA and loads models NASTRAN. We develop designs, test them, put them into production similar to the quad industry but to tighter tolerances, more advanced processes and testing since we can't have planes falling out of the sky can we.

400EX has some practical experience with some of the quads, and with others has theorems he appears to be using based on a geometrical analysis. All good but in all practicalities, every quad/racer/track has many variables that can change theories in effect. The quad geometry and the track, the rider will impose loads on that geometry that 400EX has not validated by testing methods such as stress/strain gages, other gage testing such as handle bar reaction, tire reactions, ball joint fatigue, etc, or mathematical statics(free body diagrams) or dynamics equations………Not to undermine 400EX theories, again some are proven by him and others, but just bear in mind to take all this logic(which is again very well thought out and good) and go test it for yourself. Outside of test fixtures the best way to learn about these theorems is to develop empirical data. We do this often, collect info, results over time then we put that info into computer models and use it to design, or in our quad case change our set up and note the effects. He has made that statement a few times thoughout this thread, try it yourself and I will add tabulate and track your results. Thats what I do I have set up data for most tracks we run MX and flat track set up is even more complicated with a sway bar. I think his intent was to awaken everyone as to the thought process that goes into the design and geometry of a quad and he is doing a very good job!

Still not sure I agree with you on a few things like the effect of wheel inset and tire size on bumpster..In all practicality I think it is minimal, in theory I see a conical effect that will vary depending on all the load paths imposed. Again those loads due to the variables, tracks, rider, quad geometry can have varying effects. Without a good load and kinematics model hard to say.

We have an engineer here that quit and went to work on a NASCAR team….they GPS the track solid model the car to a kinematics(motion) CATIA/NASTRAN loads model including a model of the racer for ergonomics. They can take the front end change the geometry in the computer and see the actual load on every square inch of say a tie rod, tires(hard due to the spring rates), ball joint, steering wheel, cornering, handling, etc…..then go test it and bring that data back to the computer. I have considered offering this service to a quad pro but the money in NASCAR is much greater they can afford it.

Anyway good thread….I'll try and help if I can.

Thanks!

[400exrider707]

Originally posted by TNT1
Finally read through all that and it made my head hurt…..lol! I'm a 25 yr Aircraft Design Engineer and think in way more detail than this and design products in the $750,000,000 dollar range, not $15, 000. I found the material 400EXRider707 presented for the most part very well thought out…….I can tell you have a good mechanical aptitude and can visualize geometry well. I do that all day with very sophisticated computer graphic's, CATIA and loads models NASTRAN. We develop designs, test them, put them into production similar to the quad industry but to tighter tolerances, more advanced processes and testing since we can't have planes falling out of the sky can we.

400EX has some practical experience with some of the quads, and with others has theorems he appears to be using based on a geometrical analysis. All good but in all practicalities, every quad/racer/track has many variables that can change theories in effect. The quad geometry and the track, the rider will impose loads on that geometry that 400EX has not validated by testing methods such as stress/strain gages, other gage testing such as handle bar reaction, tire reactions, ball joint fatigue, etc, or mathematical statics(free body diagrams) or dynamics equations………Not to undermine 400EX theories, again some are proven by him and others, but just bear in mind to take all this logic(which is again very well thought out and good) and go test it for yourself. Outside of test fixtures the best way to learn about these theorems is to develop empirical data. We do this often, collect info, results over time then we put that info into computer models and use it to design, or in our quad case change our set up and note the effects. He has made that statement a few times thoughout this thread, try it yourself and I will add tabulate and track your results. Thats what I do I have set up data for most tracks we run MX and flat track set up is even more complicated with a sway bar. I think his intent was to awaken everyone as to the thought process that goes into the design and geometry of a quad and he is doing a very good job!

Still not sure I agree with you on a few things like the effect of wheel inset and tire size on bumpster..In all practicality I think it is minimal, in theory I see a conical effect that will vary depending on all the load paths imposed. Again those loads due to the variables, tracks, rider, quad geometry can have varying effects. Without a good load and kinematics model hard to say.

We have an engineer here that quit and went to work on a NASCAR team….they GPS the track solid model the car to a kinematics(motion) CATIA/NASTRAN loads model including a model of the racer for ergonomics. They can take the front end change the geometry in the computer and see the actual load on every square inch of say a tie rod, tires(hard due to the spring rates), ball joint, steering wheel, cornering, handling, etc…..then go test it and bring that data back to the computer. I have considered offering this service to a quad pro but the money in NASCAR is much greater they can afford it.

Anyway good thread….I'll try and help if I can.

Thanks!

Thanks for the input and the kinds words. Most of what you're talking about is way over the head of the every day rider. I tried to keep it technical, but still understandable. I think I did a decent job of that. I would love to talk more technical with you. You obviously have better resources than I do, but I understand what you're saying and can definitely follow along.

Don't underestimate me because of this thread. I do keep technical notes on all the tracks I go to, though probably not as sophisticated as you're making it seem.

I've done a bit of FEA myself on some simple parts, but nothing as advanced as you say you can do.

I think we have more to learn here...

[IMSROLL450R]

Whatever 707 you have no idea what you're talkin about. I think your caster is messed up.

[400exrider707]

Originally posted by IMSROLL450R
Whatever 707 you have no idea what you're talkin about. I think your caster is messed up.

You spelled castor wrong...

[IMSROLL450R]

I told you its messed up!

[TNT]

Hey Guys I'm out here....too funny! I can't spell either!

K, 400 EX want you to know I don't know as much as you about a quad set up and had planned to study all you wrote again with the quad in front of me and I didn't mean to hi-jac your thread with a bunch of loads stuff...

My question is with regards to camber when the front tires are going over the track one tire will get different traction than the other, both tires will see different angles on the track. How to deal with that, find a medium?

[400exrider707]

Originally posted by TNT1
Hey Guys I'm out here....too funny! I can't spell either!

K, 400 EX want you to know I don't know as much as you about a quad set up and had planned to study all you wrote again with the quad in front of me and I didn't mean to hi-jac your thread with a bunch of loads stuff...

My question is with regards to camber when the front tires are going over the track one tire will get different traction than the other, both tires will see different angles on the track. How to deal with that, find a medium?

I'm not sure I fully understand your question. Let me explain a few things and it might make this more understandable. IMO camber isn't as crucial as it is on say pavement. The idea behind camber on a car (on pavement) is that when you turn going fast, your tire, being made of rubber, will flex. If your tire was running at 0 camber, the contact patch of the tire would become smaller. The idea to putting camber in is so that when turning hard and the tire flex's, you still maintain a larger contact patch.

Now on a quad, our tires flex a ridiculous amount, which is also good because it allows the most grip from the tire. We have soft compounds and very flexible tires. Though camber may play a small role in traction, I think the three main subjects of traction on the front tires is track conditions, tire pattern (if you have a good pattern for the conditions and also if you have a lot of tread left or bald tires) and tire air pressure.

Now what you're asking seems to be a more theoretical question. Which camber setup would provide better traction? That's a tough question to answer and again track conditions are going to play a huge role.

Try asking your question again differently, I'm sorry I just dont think I fully understand it.