Solid Rubber Wheels - rating?

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Solid Rubber Wheels - rating?

Post by internetscooter » Fri Apr 16, 2010 10:21 am

I may have a solution to my small wheel tyre speed rating problem by going with solid wheels. Instead of the a tyre, the rims will have permanently fixed solid rubber or polyurethane compound.

How would this work with speed rating requirements for racing? Would these be considered high speed tyres?

Even without the speed rating these will have the advantage of:
* less rolling resistance
* more mass and more centrifugal force holding the scoot straight
* more tuning of wheel size for improved gearing ratio
Paul
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Post by David Leikvold » Fri Apr 16, 2010 2:56 pm

Scooter,
I had considered the same solution to the problem of finding small diameter tyres for a light weight special construction car that I probably will never build.

I think the only realistic way to get homemade wheels/tyres approved would be to build a jig that spun them at whatever speed you needed so you could prove, firstly to yourself and secondly to the scrutineers that they were up to the job. I had imagined mounting them on a swing arm loaded with weights to replicate the actual load on the wheel and then spinning it on a single roller with drive from an electric motor. In your case it would be far simpler to just sit the bike on a pair of rollers with the solid wheel/tyre fitted and then run the bike as hard as it could go, which would be a bit faster than actual because there'd be no air drag. Prove the speed it's turning the roller by whatever means available to you and if the tyre doesn't fail at speed and still looks good when it's stopped then you'd probably stand a good chance of being allowed to use it. If it does fail you can always go back to the drawing board and console yourself with the fact that at least you weren't at speed when it happened. Make sure you get the testing done and approval in hand well before Speedweek.

Cheers
Dave
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Post by Reverend Hedgash » Fri Apr 16, 2010 7:21 pm

Paul,

the So-Cal GM bellytank had the same idea for their mark one unit but after testing they resorted back to the Goodyear Landspeeds for their mark 2 car.

Whether this was because of rules or what I don't know but they trumpeted them pretty loudly when they started so it must have been a good reason to change back.

Perhaps pursuing this history will help you make a decision.

Roscoe's Aussie invader had solid wheels but it wasn't wheel driven so that is not a good example and I believe they had tracking problems...

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Post by internetscooter » Fri Apr 16, 2010 9:00 pm

Looking at the Australia Standards for tyres, the testing has to be for at least 10 minutes to allow the heat to build up (heat caused by deflections being the thing that causes the damage).

I had hunted for test facilities in the past but drew a blank in Australia. It would be nice if an informal test on a dyno would surfice (i.e. run at top speed for 10 minutes with a dummy load).

The reason though I was thinking the solid wheels is that in industrial machinery you should be able to specify "I need a roller of X diameter that can work all day at 3000 rpm with a 200Kg load"... i.e. buy a custom solid wheel with a documented speed rating

My current tyres are rated to 180Km/hr with a caveat on reduced load and increased tyre pressure. This will probably do me but maybe not ;) I also know people planning on running scooters in Aus and Bonneville (pending tyres). A Vespa is hard to get up high due to gearing but Lambrettas are getting 136mph though they couldn't run on the salt http://www.100mphscooter.com/100_mph_speeds.html

I'll see what I can dig up about the So-Cal GM bellytank.
Paul
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Post by Last Minute Racing » Fri Apr 16, 2010 9:16 pm

WOW 136 mph on a scooter :shock:
Still have 10 inch wheels?

Thanx
Dave
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rubber donuts

Post by David Leikvold » Fri Apr 16, 2010 10:05 pm

Paul,

The ten minute standard isn't really relevant to your situation as you would only be going flat out for somewhat less than two minutes. And if you want someone to make these tyres/wheels for you, you'll be horrified at the prices quoted, assuming you can find anyone interested in doing the job in these litigious days.

My plan, and I make absolutely no guarantees as to whether it works or not because I never tried it, was to make integrated wheels and tyres. I intended to turn up the centre of the wheel in thick aluminium plate and then bolt that to several concentric rings of aluminium that were sandwiched between several (minus one) thin donut-shaped sheets of rubber, each probably no more than 10mm thick. The retaining bolts (at least a dozen, I'd guess) would pass through all the rubbers and the aluminium discs would have small wedges turned in them to help the rubber resist centrifugal force. To further reduce the effect of the centrifugal force I intended to have the wheel centre come out to the full diameter of the aluminium rings so that the bolts had no chance to flex radially. The rubber would only protrude past the discs by about 4 or 5mm. I had intended to try rubber sheets from Clark Rubber. This is quite soft but they don't have to last long. Perhaps someone else makes harder rubber that might be more useful.

This idea means the wheels and "tyres" could be made in your workshop on a lathe with a decent swing and a hydraulic press. The lathe makes the aluminium wheel parts and a mild steel cutter that stamps out the rubber donuts, complete with a wad punch setup include in the tool to cut the retaining bolt holes accurately. A mill with a dividing head would be very useful for drilling the holes in the aluminium discs for the retaining bolts. The press is to do the stamping job. As you'd need to replicate the cross section shape of a standard tyre you would need to make each aluminium disc a different outside diameter to approximate the circular cross section shape and then when the wheel is assembled put it back in the lathe and get stuck into the rubber donuts very carefully with an angle grinder to produce the final shape you need.

That's my two bob's worth. I know the idea seems complicated but I think it would work because the wheel would stay rigid, as would the rubber, the rubber edges wouldn't really get the chance to squirm around too much, the rubber is easily and cheaply replaced and you could make it the exact same size and shape as the original tyre so that it looked "right", especially if you black anodised the discs. Please let us know what you finish up doing.

Cheers
Dave
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Post by internetscooter » Sat Apr 17, 2010 10:38 am

Dave - Yes 136 mph on 10 inch wheels! http://www.flickr.com/photos/21197025@N03/sets/72157622072627422/
Image
Image

David - That would probably work. I have the advantage of split rims. I have been informed that I can vulcanize rubber permanelty right onto the rims with an oversized mould and then finish the shape with a lathe.

Reading the rules the above would make me a deviate ;) Which is acceptable as long as I can provide some data.

7.B.8 Any tyre deviation must be submitted to the motorcycle scrutineer chief scrutineer, with sufficient supporting data to justify a deviation in writing 60 days prior to a meet.
Paul
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revs

Post by David Leikvold » Sat Apr 17, 2010 6:43 pm

Paul,
The moulding straight onto the rims would certainly work for low speed applications, e.g. forklifts, trolleys and such, but do you know what will, or might, happen when your small diameter tyre is spinning at a kazillion revs? Can the rubber withstand that centrifugal force without reinforcement? If it got any kind of small split or tear I'm concerned that it would peel right to the core in very quick time and with serious consequences. If it was me, being a cheapskate, I'd want to have a pretty good idea that it was going to work consistently before I committed to the cost. Good luck anyway, I commend you for thinking outside the square.

Cheers
Dave
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split rim

Post by David Leikvold » Sun Apr 18, 2010 8:17 am

Paul,
The split rim might be the answer. If you were to turn up a plate to go between the rim halves you could have it go close, but not too close, to the original OD of the tyre, turn grooves in both faces of it, sandblast the surfaces and have lots of holes in it so that the rubber can hang on better. If you started with a thickish plate (say 20mm or so?) you could turn it down in the centre so that the finished wheel wasn't much wider than the original and at the outer edge you could make it T-shaped or even anchor shaped to hold the rubber better. You might even put lots of small steel rods evenly through the plate in concentric circles to enhance the effect.

Cheers
Dave
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Post by Dreamliner 200 » Sun Apr 18, 2010 9:01 am

Hi Paul, that one in the Flikr photo's, is it on Nitrous, or is that gas bottle being used to vary the expansion chamber volume?....

Interesting! :P
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Post by internetscooter » Sun Apr 18, 2010 11:42 am

Good tip Dave - I will keep that in mind if I go down this path. I'd guess having a balanced wheel would also be crucial.

The Lambretta runs on Meth and there was no mention of Nitros in the story I read... so yes that must be the gas bottle for the expansion chamber. He said it allowed him to tweak the power and increase top end speed by about 6 mph. It changed the tuned length by 50mm.
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balance

Post by David Leikvold » Mon Apr 19, 2010 5:37 pm

Paul,
Yes, balancing the wheels would be crucial anytime, but especially on an uneven surface like salt. From the photo it looks like your wheels bolt to a wide hub flange/brake drum. If a good balancer for the wheels is commercially available at scooter shops, use it. If not, you can make a simple but effective balancer yourself. These are particularly suited to narrow wheels such as yours. Turn up a fixture that holds the wheel square and concentrically on a replica hub on an axle. If you want, you can have bearings holding the hub on the axle. Some is good, more is better (too much is just right!). At each end of that horizontal axle (the length is irrelevant by the way) have a roller bearing (without seals, they just create drag) and rest those two bearings on another pair of them at each end that at are securely attached to a stand that allows the wheel/tyre to spin freely. Design the stand so it can be clamped to a bench or in a vice so it can't move.
With little or no friction because of all the bearings, when you spin the wheel gently it will always stop with the heaviest part of the wheel at the bottom. You can then put small stick-on weights directly opposite at the top of the wheel. Don't peel the sticky protector off straight away, attach the weight with a little bit of racer tape first until you know it's in the right place. When you can't get it to stop in the same spot twice, it's ready to enjoy.

Cheers
Dave
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new idea

Post by SPOOK » Tue Apr 20, 2010 1:33 am

Great ideas both Ross and David. My 2 cents worth is a carbon-fibre disk slotted up from the outer edge to hold a rectangular section of hard poleurathane annulus sliced in half so it can be placed in the slotted disc to form the tyre. the tyre can be made any width and protrude out from the disc any distance you like. the tyre would be cross bolted to secure it in the slot of the c/f wheel disc with titanium bolts and washers can be added on certain bolts the obtain perfect dynamic balance.

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Post by nitro-nige » Tue Apr 20, 2010 9:54 am

Does it need to have a tyre?
I'm not saying it doesn't but there are few guys who've done it without.
Image

We make wheels at work that get used in crane carriages. There's a company the moulds a urethane tyre on it for us. If you turned the hub with a T-slot on the circumference the urethane should fill into and be locked there. That should reduce the chance of delamination.

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Post by Greg Watters » Tue Apr 20, 2010 1:59 pm

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

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