Solid Rubber Wheels - rating?

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David Leikvold
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Post by David Leikvold » Tue Apr 20, 2010 3:43 pm

Spook, your titanium bolt idea is inspired. Having the wheel perfectly balanced without the use of wheel weights would be ideal. There's no reason why the standard wheel halves couldn't have another annular ring on either side of the central one, just to help out. They'd need to be a smaller OD because of the curvature of the tyre but all three could be bolted together with tiny bolts to hold the moulded tyre assembly rigid. And there's no reason why the central ring couldn't be made from 25mm aluminium plate so that it could have several substantial cross ribs turned into it, not just one at the outer edge. I'm not against the idea of carbon fibre, I'm just thinking of ease of making the part.

Nige, is polyurethane sticky or slippery? I seem to remember Fulcrum poly bushes being very smooth and hard out of the mould. I suppose if the tyre was turned into almost finished shape on a lathe and hand finished with an angle grinder (yikes!) the surface would be more like a slightly used race slick. The reason I mention angle grinder is that it would be easier to make the curved shape with one and I only very vaguely remember that the polyurethane needed something special to cut it properly. I think it may have been a very high lathe speed and a special shaped tool but you'd have to ask someone who new exactly what to do. Paul mentioned getting rubber vulcanised straight onto the rims anyway so maybe the poly idea isn't happening anyway.

I can't get excited about using Jack Costella's aluminium billet wheels on a bike, I think they'd slide all over the show at both ends of the bike. Rosco McGlashan had to have V-shaped "tread" on his car to keep it in a straight line. Now, granted he was going a fair bit faster than a Vespa but you get the idea. There has to be something a bit grippier than aluminium running on the salt.

Of course the angle grinder idea could be ditched if Paul went to the trouble of making a mould for the finished tyre, complete with the reinforcing discs and then just bolted the finished product straight onto the wheel halves. It'd be a lot more work but the finished product would look better and need almost no hand finishing afterwards. A mould would also make it easier to put a slight tread on the tyre if that was deemed worthwhile.

Greg, I suspect that Paul wants to keep the bike as much Vespa as possible. If he went away from the OE 10" rims to an off the shelf speed rated tyre he'd need 17" rims and then it wouldn't be a really fast scooter anymore, it'd be a slow motorcycle with a scooter engine.

Paul, I think the "sufficient supporting data to justify a deviation" could well be you running the Vespa flat out on the rollers while the motorcycle scrutineers watched. Perhaps you should get in touch with Gary Baker before you decide on a final plan.

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Dave
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Post by grumm441 » Tue Apr 20, 2010 7:47 pm

Greg Watters wrote:some of this sounds a little like racing on recaps :shock:

Probably the best place to ask about solid wheels is Landracing.com, seen lots of stories on there about handling probs from solid wheels,

Why are you limiting yourself to particular size tires, can't you find the best tire for the job and work around that


Greg
one of the problems with the vespa PX200 is that if you go above 3.50 x 10 on the rear it rubs on the clutch cover.
Solid wheels would be nice but a PX200 is not a fine handling machine with good suspension, to start with and I think this would only make it worse

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Greg Watters
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Post by Greg Watters » Wed Apr 21, 2010 7:49 am

There is a point though where you have to modify things to go faster, maybe this is that point on the Vespa , to take it safely to a new level
Personaly i find the thought of doing 100+ mph on 10" wheels rather scary :lol:

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wring its neck

Post by David Leikvold » Wed Apr 21, 2010 9:05 am

The first time I rode a scooter I found it very disconcerting with my feet in front of my knees, it just felt wrong and I couldn't get a proper grip on the bike. The top speed of 61km/h down a greasy mine shaft didn't help either, but the tiny wheels also made it very darty so maybe the whole package makes more sense in its proper urban environment.

And you're right Greg, there does come a point where big mods have to be made for bigger speeds. But that's the beauty of LSR, anybody can choose whatever niche vehicle they want and wring its neck as much as they want and nobody minds. For me, it's the freedom to be as technically innovative as I want that appeals most to me and I suspect most other members too. That's why I like to offer my two bob's worth to anyone who asks. Sometimes it works, sometimes it doesn't.

I think Paul may be chasing that 136mph record. After that, who knows? Did you ever see that bike that had a couple of dozen chain saw motors? Maybe in a few years Paul will get a few Vespa motors, chain them to an appropriate gearbox, put them in a custom lay down chassis with Z rated tyres and see what happens. No guts, no glory. :)

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Post by Dreamliner 200 » Wed Apr 21, 2010 12:09 pm

Interesting thread this!

Nige, I hadn't really seen the front end of Jack's 788 before, inline steering eh! :shock:

Here's one of the new 8080 Bike engined car

Image

How would a car be viewed if it turned up at Gairdner with this sort of set up?

I know the rule book refers to any special wheel / tyre has to be approved so as not to cut into the salt, the profile of the Nebulous Thereoms cars solid wheels seem to have a smooth face and a real gentle edge to them......

Comments?

Hope I'm not hijacking the thread Paul!

I guess it's all relevant :P
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Post by grumm441 » Wed Apr 21, 2010 9:22 pm

And they don't actually turn but just move from side to side
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SPOOK
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solid rubber wheels

Post by SPOOK » Wed Apr 21, 2010 11:35 pm

So if the front wheel moves to the left do the airodynamics move the vehicle to right?

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left right left right

Post by David Leikvold » Thu Apr 22, 2010 12:47 am

200, I'm going a bit off topic here but I'm sure Paul won't mind. These threads always evolve while they last. Those flat billet wheels from either Nebulous Theorem 3 or Neb 7 (the 8080 bike) wouldn't mark the salt anymore than any other "tyre" so I can't imagine you'd be refused permission to run, but as the rule says you have to get approval well before Speedweek.

If you (or any other interested readers) haven't seen a close up shot of the steering mechanism of Neb 3 (the orange car with the dual front wheels) it is very clever and wouldn't be expensive to make either. If I had a picture I'd post it, but I don't so here's a thousand words instead. Maybe someone else can find a picture.

It starts with handle bars with a vertical centre bolt so the bars are pushed forward and back to steer the car. This is much smarter than a steering wheel in this case because space is really at a premium in this car. The top of the pivot bolt has what looks like a bicycle chain sprocket attached and a chain goes forward just a couple of feet, if that, to a matching sprocket on a longitudinally and centrally mounted steering rack with a vertical pinion shaft pointing up. The rack only has one steering arm which goes all the way to the front wheels via assorted shafts, universal joints and support bushes. It moves the lateral steering arm for the closest of the front wheels backwards and forwards. Attached to that same point is a short white rod (it is visible in the picture alongside the back wheel) that runs forward to a bar that pivots in the centre and reverses the motion for the opposite-facing front wheel. This connects to another short rod that connects to the lateral steering arm for that front wheel. I believe this same setup was used on Al Teague's car too, but I haven't ever been able to find any photos of the mechanism, just photos of the front wheels under the body in the same staggered layout as Neb 3.

Unless I am very much mistaken, the movement of the handle bars is restricted to somewhat less than 90* in either direction (much the same as the bottom of a go kart steering column). If that's correct, the only change I would make to Jack's system would be to do away with the chain and rack setup and connect the handlebars directly to the longitudinal steering rods. If I'm wrong and the handlebars can turn as much as the pinion would in any other steering rack then the rack setup could be used as Jack designed it.

If you wanted to change the steering ratio up or down that could easily be achieved by installing an idler somewhere along the long shaft with various holes in it and a single pivot. If the rear rod was mounted closer to the pivot than the forward rod the ratio would increase slightly (more steering of the wheels for less turn of the handlebar) and vice versa.

In a photo I found on the Landracing gallery from Speedweek 2007 (I think) the single front wheel of Neb 7 had an inline steering damper from a motorcycle attached, which seems smart to me. It isn't in the most recent photo with the hose (see the threaded vertical bush behind the little bulkhead) but neither is the front of the chassis which looks to have been cut off. The bellcrank located immediately behind the billet wheel significantly reduces the steering ratio. I particularly like the way Jack has finished the steering mechanism with the two female rod ends and (presumably) a short section of good quality bolt thread to join the two simply and safely.

200, if you intend to build something like Neb 2 for yourself I'd probably use the Neb 3 steering setup rather than the more conventional Neb 2 setup, if only because it offers you the option of a very narrow nose on the car. I'm guessing because you use Neb 2 as your avatar that you're entirely familiar with Rick Yacoucci's website, www.yacoucci.com . For those who aren't it is probably the best LSR website out there, especially for those interested in the technical details of the car. He provides remarkably comprehensive specifications and hundreds of photos.

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Dave
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Post by David Leikvold » Thu Apr 22, 2010 1:15 am

Spook, I had always imagined that if the wheel was pointed left the vehicle (Neb 7 is actually a motorcycle) would go left but now you've got me wondering. Would it actually counter steer like a real bike? The centre of gravity is all wrong for it to do that easily. The whole thing is only about knee high so aerodynamics wouldn't play much of a part in it. Are the handlebar links set up to reverse the steering so that it goes the way it's pushed? What would it do if it leaned in a crosswind? The bodywork is only about an inch off the salt with it at rest so a big lean could quickly feel like the non-existent side stand was still down! Would the square section of the front wheel make it feel as bad, or worse, than a bike with a worn flat rear tyre when it leaned? I know it doesn't use those low speed stabilising wheels that other similar vehicles use, but relies on the front wheel to hold it up.

I think that flat section "tyres" like this might be better suited to four wheeled vehicles such as Neb 3. At Bonneville Neb 2 uses taller aluminium billet wheels with a lozenge shaped cross section with very rounded shoulders. At El Mirage it used those 5" Goodyears that Top Fuel used to run in the 1990's. What a shame they aren't speed rated, they'd sell plenty of them if they were. But I digress. I have no definite answer to your question, perhaps one of our American readers can help.

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Dave
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Post by Dreamliner 200 » Thu Apr 22, 2010 10:26 am

Crickey David, I thought I had spent some time studying the Neb cars photo's ! You have obviously given this some thought!

Yes I have looked at these cars too, the biggest stumbling block is the front wheels for a low aero solution, plus the whole flat bottom / rounded bottom debate!

My plans are still 'dreams' at the moment, but I am on the way, getting to the salt this year was a big step! Now though, the salt fever has me in it's grip :shock: who knows where it will end.

I think a trip to Bonneville will have to be included, then I can go and talk to some of these guys in person, I mean, what does it feel like to be steering one of these things at 200 or even 300 plus mph :shock:
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Post by David Leikvold » Thu Apr 22, 2010 10:39 am

200, have you ever seen any in-car video from the Indy 500? They barely move the steering wheel at all for the whole time. I reckon that's what it feels like at 300mph on the salt too :lol:

Flat bottom? Round bottom? I much prefer something like Kylie's! On a car as skinny as any of Jack's I don't think it would make much difference. Despite that, my personal preference would be to have a very slight V shape just to tell the air not to linger under there. No science behind this, just a hunch.

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Post by internetscooter » Thu Apr 22, 2010 2:46 pm

I hadn't noticed the thread being hi-jacked ;) I wasn't getting notifications or maybe I missed one... anyway...

Graham the bigger wheels are possible without rubbing the clutch cover as the wide tyre kits shift the whole engine sideways (you cut the engine mount). The only trouble is that the speed rating letter I have is only for Sava and they don't make a size for the wide tyre kits.

The other problem is that I'd have to shift all the modifications sideways too.

I plan to take the scoot to Heathcote Park soon to see how handles the quarter mile. Then try out a 33 tooth DRT 4th gear at Phillip Island... then I'll know if I need to worry about tyre rating :)

On with the hijacking :)
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Post by David Leikvold » Thu Apr 22, 2010 4:43 pm

Paul, is the wider tyre any bigger in diameter? If it isn't it won't help much. If you did go with one of the solid tyre options you could always increase the diameter of the rear tyre only so the mod wasn't as obvious. I'll be very interested to hear how the bike goes around Philip Island. I was just on a Vespa forum looking for info about tyres and one unkind soul said they "all handle like crap", a sentiment that doesn't seem uncommon. Is there any easy way to fix or just improve the handling? Perhaps a couple of big diameter thin wall steel tubes welded together and connecting the front and back of the bike so it can't flex so much? Might make riding it at Vmax much nicer.

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Post by internetscooter » Thu Apr 22, 2010 6:23 pm

The most likely scenario for a custom wheel is bigger diameter to improve gearing.

The Vespa is designed for tight turns so it feels pretty scary at high speed, however it is way more stable than it feels. I can quite comfortably ride at 100km/hr hands free leaning back on luggage (and even overtook a car once like this for fun).

The salt is pretty scary though because I haven't ridden enough to get a feel for the difference between fake scary and real scary :)

There is a mod that will increase front trail, which I will consider if I need to.
Paul
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Post by grumm441 » Thu Apr 22, 2010 7:05 pm

internetscooter wrote:
There is a mod that will increase front trail, which I will consider if I need to.


Does that mod include a turnbuckle and a bit of plate?

If you can put a wider tyre on it that's great, because the wider stuff, like the 100/80 and such have a higher speed rating than the 3.50
On another thing, I had Tony Scerri in during the week with some of the new tubeless rims from you know who. Much better quality and very easy to put a tyre on.
And today someone from Sydney rand to ask me about bringing a turbo majesty and a supercharged GP200
G
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