Crazy, oddball, whacked out, dirt bike ideas . . .

[XRpredator]

This is kind of a light-hearted attempt at humor (though I am half-serious about some of this) for the Advanced Tech forum. I was just wondering about some of these ideas for dirt bike parts:

• Carbon fiber rims
• Hollow shock springs
• Air forks & shocks (I was intrigued by the article in <gasp!> MXA)
• Helium filled innertubes
• Helium filled air suspension
• Leaf spring rear suspension
• Torsion bar rear suspension
• Carbon-fiber handlebars

That's all I can think of for now (I've got all sorts of ideas bouncing around my brain bucket, I'll think of them later)

So, Rich and Eric (and anyone else), whaddya think?

 

[yzeater]

So I'm not the only one who thinks like you. Some more of my ideas include

1. Carbon fiber or Titanium engine casing
2. Carbon fiber exaust (including expansion chamber)
3. Carbon fiber plastics (you know what I mean)
4. Carbon fiber frame
5. Tires made of something besides rubber
6. Bigger c/s sprocket than rr sprocket (for desert racers)
7. Four stroke exhaust on a Two stroke or visa versa
8. This isn't extreme, but no airbox
   [/list=1]

 

[RM250Rida]

I like the helium in the tires thing. I don't think I'd do it to my bike since I already have a hard enought ime keeping the front wheel on the ground. But I think it'd be cool to fill both front tires on a 4 wheeler or something.

 

[gibbs_6]

Pretty cool ideas;)

 

[woody51]

The race car guys use Nitrogen to fill up their tires. Not because it weighs less but because it doesn't expand as much when it heats up and gives them a more consistent tire pressure. I think that maybe Helium might expand too much.

How about some Magnesium engine covers. They are already using them on the street bikes.

 

[Buzz Bomb]

Pro Circuit makes magnesium engine covers.

YZeater, I like your idea of carbon fiber plastics. Those would most likely be a hot seller.

 

[MoO_coW]

I did this once but it erased it so lets go again

• Carbon fiber rims: They have them for quads and there suppose to be awesome
• Hollow shock springs: :scream:
• Carbon fiber or Titanium engine casing: I don't see any advantages except in weight but the cost would be crazy
• Carbon fiber exaust (including expansion chamber): They already have silencers and as far as pipes, Metal bends, carbon fiber breaks
• Carbon fiber plastics (you know what I mean): It would cost alot of money and weigh more than plastic-it would look cool though
• Carbon fiber frame: its being done
• Tires made of something besides rubber :confused: like what?
• Bigger c/s sprocket than rr sprocket (for desert racers) :think
• Four stroke exhaust on a Two stroke or visa versa: that wouldn't
  work :confused:
• This isn't extreme, but no airbox :eek:

 

[VintageDirt]

You couldn't use helium in your tires/tubes. It would just leak out through the rubber. It's a very small molecule. And besides, you wouldn't save enought weight to even notice.

 

[_SOLO_]

How about somewhere to put a nitrous bottle on there? Of course with some CF mounts. Of course I won't be using the nitrous for the bike. I am pretty sure that nitrous oxide is the same thing as laughing gas. I have to have something to put me out of my pain when I fall.:confused:

 

[XRpredator]

Originally posted by VintageDirt
You couldn't use helium in your tires/tubes. It would just leak out through the rubber. It's a very small molecule. And besides, you wouldn't save enought weight to even notice.

I know;) , I was just being silly with the helium in the tires. But some of the others might work . . .:think

The air suspension in that last MXA was very interesting. And the hollow shock springs--think about it. You take a hollow tube and turn it into a spring. It could work!:confused:

 

[MikeT]

Sure you could make a hollow spring, but to get the same spring rate I bet the diameter of the coil would be bigger, how much, I don't know.

I don't think that you'll see Carbon fiber handlebars because when carbon fiber fails, it does so quickly. I think that the handlebars would snap under load. If anything you'd want them to bend in failure mode. Thats why they put steel rebar in concrete beams. I don't have the value handy but I believe the modulus of elasticity for carbon fiber is very low. I think the same might be the reason for carbon rims although someone said it is being used for ATV rims.

Just my thoughts, I have never designed anything with carbon fiber but I think those might be valid reasons. I'm sure some materials people will be in here to set us straight.

 

[OnAnySunday]

Originally posted by XRpredator :

"[*]Air forks & shocks (I was intrigued by the article in <gasp!> MXA)"

Uhhh...........
Older bikes had air assisted forks. (both my '79 YZ & '82 XL have 'em)
And you "yunguns" poked fun at 'em!
:eek:
Now complete AIR forks? (ie: no springs??)
OIY VEY!!:confused:

 

[will pattison]

i would sort of like to have a cup holder...you know, for when it's really hot and i want to carry some ice water.

:eek:

 

[marcusgunby]

Carbon fibre replacements for the plastics have been used but were banned by the FIM as they could spear you in a accident.:o

 

[MikeT]

Marcus, am I on track with my modulus of elasticity reasoning???

 

[XRpredator]

Okay, to heck with the bars, but the wheels should work. I read a test in one of the "performance couch" (i.e. ATV) mags of the carbon fiber wheels, and they said they performed flawlessly.

And don't I remember a carbon fiber swingarm on David V's bike in Europe a few years back? I also seem to recall the leaf spring rear suspension . . .:think

 

[MBFTY]

Carbon Fiber Wheels

Carbon Fiber wheels are being used in the ATV market with great success. The only drawback is the ungodly high price... They go for about $500 a piece!

I have seen specially created Carbon Fiber and Fiberglass fenders on show bikes and quads, but you wont see me riding with them on mine! The last thing I need is a fender sticking out of my gut after a wreck... OUCH!

 

[MikeT]

Originally posted by XRpredator
Okay, to heck with the bars,

Predator, LOL, you are funny! I can feel your excitement about these ideas through the screen. I bet by the time this is over, you'll have some body fabricating this stuff. Go for it!!

More power to ya! :)

 

[yzeater]

Mag wheels on a big bore

 

[will pattison]

actually, the HIGHER the modulus of elasticity, the stiffer a material is.

aluminum: about 10 million psi
steel: about 30 million psi
carbon fiber (standard modulus): about 30 million psi also.

you are right about concrete, but with the pre-stressed variety, the rebar is stretched while the concrete is wet. after it's dry and the tension is release, the bar attempts to return to it's original length. as the concrete wants to go along, tremendous compressive forces are built up, and that's when concrete is strongest. it sucks in tension.

wp.

 

[David Trustrum]

Free thinking is a good idea, but there is nothing new under the sun.

Air has never been a successful suspension spring as it has an exponential curve (gets very stiff real quick). This is why linear springs are the go now that we have realised that all this progressive springing stuff linkages is nonsense & the important thing is the damping & being able to alter the high & low speed (of the shaft not the speed of the bike) characteristics.

Nitrogen in tire is used in road racing by the really keen as well for the reasons above. However dirt tires & tarmac tires operate differently & temperature change isn’t a big concern.

Carbon fibre body work will be lighter, but brittle & possibly dangerous as stated above. You have to use it in a way that takes advantage of it’s stiffness to weight advantage. Big diameter thin wheels over jumps? Think you would have to make them so thick that there would be not weight advantage.

Mag side covers, well heck go have a look at your grandad’s yz & you’l find ‘em, it’s written on the side. Carbon fibre? Sure why not, streetbike aftermarket guys have been making them for years.

Thing about springs is they have to be made from spring material. Also if they were hollow they’d tend to crease & it’d be game over.

Large hollow axles? Big streetbikes are doing it. the Britten had enormous axles & Carbon fibre forks (which failed spectacularly the first test ride & had to be redesigned). Also had c/f wheels, frame (latter versions had mostly just the engine as frame), but how about repositioning the radiator?

Serious suggestions:
If you want your tires lighter only pump them up to 6 pounds saving ~ 6 pounds a wheel.

Unleaded fuel must be lighter?

 

[Jon K.]

Air shocks have most certainly been done. The Fox shox were totally air sprung, and about the best shock around for 15 minutes in 1974. They had a high pressure side and a low pressure side seperated by a bladder.There were also Fox Forks. Does anyone remember if they were air sprung?

 

[Kramer]

Ever see CF ski poles? They can nearly bend end to end without breaking, .25" or so in dia., and are a good bit lighter than their Al counterparts. Cost an arm & a leg, and who wants to land on a splintered CF stick if it gets broken.

How about an Al fly rod?

With good engineering, composite materials can behave in many different ways. CF is only one of many types of fibers used. You can also orient the properties in the direction of max stress. In other words you don't need to add alot of weight making a part with uniform strength, make it as strong as you need in each direction.

 

[Jaybird]

With pressure release valves, the big problem with air shocks seems to be (or going to be) a thing of the past....

David, quite a serious suggestion on the 6lbs air.....:silly:

 

[MikeT]

Originally posted by will pattison
actually, the HIGHER the modulus of elasticity, the stiffer a material is.

aluminum: about 10 million psi
steel: about 30 million psi
carbon fiber (standard modulus): about 30 million psi also.


wp.

It must have to do with ductility then, Steel is more ductile than aluminum and I don't think CF id ductile at all. That must be it.