Solid Rubber Wheels - rating?

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internetscooter
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Post by internetscooter » Thu Apr 22, 2010 8:11 pm

The mod is an extended fork link.

What tyres have a higher speed rating? You have to go pretty big for the speed rating to go up above P (150km/hr). The wide tyre kit can take a 130/70/10 Schwalbe, which has a higher load rating but they haven't responded to my request for an alternative rating.

turbo majesty and a supercharged GP200!? I guess I'll have some competition as I am still planning to enter that class.
Paul
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left field

Post by David Leikvold » Thu Apr 22, 2010 11:13 pm

Paul,
I don't know how well this would work but if you hunt around hard enough you could probably find a 145SR10 tyre, which was a size originally fitted to Minis many years ago. A quick Google search shows Yokohama, Falken and Dunlop too. From memory it went on a 3.5" rim on a standard Mini and 4.5" on a Cooper S. I don't know how it would handle on a bike, you might have to get the shoulders buffed and really over-inflate it to create a more circular tread section but at least it has the S speed rating, which is about all you'd likely ever need. The Falken is supposedly 392mm nominal diameter and 140 section width. If you can make it fit you might have both your problems solved.

Antique Tyre Supplies in Melbourne lists a Dunlop steel radial in an Aquajet tread pattern in 165/70SR10. Bridgestone lists one too. That's probably much too wide but at least you know it exists. An annular spacer between the rim halves and longer studs holding them together would make it fit on the rim. If you do that go with the narrowest rim option for the tyre so that it bends the tread face more into the shape you want. OD is given as 19.44", which is exactly the same diameter as the 145SR10. Tubes are still available so your split rims wouldn't be a problem. The 165 would look good from behind! Good luck.

If the bike is disconcertingly twitchy at speed maybe a steering damper would help. And from right out of left field, I was also wondering if incorporating a heavy steel gyroscopic flywheel on the front wheel might help stabilise it at speed. With such a small diameter it probably wouldn't have much effect but you never know until you try. Just a thought.

Cheers
Dave
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SPOOK
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solid rubber wheels

Post by SPOOK » Fri Apr 23, 2010 2:32 am

Paul,it is correct that scooters handle extremely bad at speed. If it was my machine I would lengthen the frame quite a lot. Bring the seating position forward of the motor and that way you could sit much lower and further to the front thus increasing stability,lowering thepoint of gravity and reducing frontal area.The change of trail is an advantage also. If the scooter has a tubeular spine frame and it is lengthened maybe the horizontal part of the tube could be used as the fuel tank thus getting more weight closer to the ground.

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Post by internetscooter » Fri Apr 23, 2010 10:07 am

It would be extremely difficult to mount a mini tyre front and back... though necessity is the mother of invention ;) The gyroscopic effect was also what I was thinking about with the rubber wheels. I might test it out by filling some wheels with water to see how that feels.

I have s steering damper as per the rules but I don't really like it. It just makes the steering feel weird... though I am used to weird so maybe it feels normal ;)

I can't change the wheelbase as that would put me in a different class, however I have shifted everything heavy forward and low. The radiator is directly behind the front wheel (which also brings the centre of pressure low too). I have even forward mounted the expansion chamber with a swivel joint. It's sits right between the wheels and reduces the unspring mass on the rear.

As is the scooter is now it is way more stable than standard. So I am pretty happy with it, though at higher speeds it is still unknown.
Paul
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more guessing

Post by David Leikvold » Fri Apr 23, 2010 11:12 am

Paul, I'm guessing that the fundamental issue with the poor handling is the shape of the frame allowing the front and back halves of the bike to each do as they please. I once had an example of that in a VW convertible that was chopped by a "professional" workshop in Victoria. Their idea of effective floor pan reinforcement was a single 1" square tube bolted along each edge of the floor pan. The front half of the car twisted visibly as you drove :shock:. I never got back in that one!

Are you allowed to put any kind of reinforcing across the top of the footwell? Even a single piece of 2" round tube would be a major improvement to the strength of the frame and wouldn't necessarily make the bike look too modified.

Cheers
Dave
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Post by internetscooter » Fri Apr 23, 2010 12:51 pm

The frame seems pretty rigid. However I am boxing in all the exhaust and radiator with aluminium channel - so the complete undercarriage is re-enforced. If I was really worried I could put a bar between the headset and the seat.
Paul
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SPOOK
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solid rubber wheels

Post by SPOOK » Fri Apr 23, 2010 6:10 pm

Paul, Have you read the book "motor cycle chassis design: the theory and practice" by Tony Foale and Vic Willoughby? There is a wealth of info. on every thing from scooters to streamliners. If you want a read of mine ring me on 95833450,I am in mentone, and I can drop it at your place. Cheers Russell.

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wet

Post by David Leikvold » Fri Apr 23, 2010 6:34 pm

Paul, your idea of filling the tyres with water would, assuming the tyre was perfectly round (most aren't), also do a good job of balancing the wheel. If the tyre wasn't perfectly round it would make it worse.

More importantly, I'm concerned that the extra weight of the water would dangerously increase the centrifugal force on the tyre. Might be something only worth trying on rollers just in case.

Cheers
Dave
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Post by Greg Watters » Fri Apr 23, 2010 8:10 pm

I fill my tractor tires with water for ballast, i think you will find water being non compressable and rubber changing shape due to load will give you a bounce... rough guess ... starting at around 80kph

think you guys may have covered it before but aircraft tires ???

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bounce

Post by David Leikvold » Fri Apr 23, 2010 9:28 pm

Greg, you're right about the bounce. If the water filled and perfectly round tyre was spinning in air as opposed to running on salt, it would spin without wobble. But running on salt with the tyre going up and down as it crosses the small undulations in the surface would generate random movement in the carcass of the tyre. The displaced water would be thrown at the other side of the tyre and the out of balance vibration would never stop, in fact it might even get worse and worse once it starts.

I had a quick look at www.aircraftspruce.com for current tyre info. Ten inch tyres are not common. Goodyear makes a 6.50x10 8 ply with a 160mph speed rating which weighs 16 lb and costs $US254.95. The tube is another $US77.25! I think it would be an even bigger diameter than the Mini tyres (no dimensions were given) and would mean a complete redesign of the rear end of the bike, which would include increasing the wheelbase, something Paul doesn't want to do. At least the weight of the tyre would probably provide that gyroscopic stability we were looking for.

This is starting to make a turbo Hayabusa look like a walk in the park :wink:

Cheers
Dave
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Post by internetscooter » Fri Apr 23, 2010 9:51 pm

yep - I've already looked through aircraft tyres. Military ones were the most promising but would be difficult to fit http://www.goodyearaviation.com/cfmx/web/aviattiresel/details.cfm?sortorder=50#FB

The water was just to see what a solid tyre would feel like. Though the comments indicate that it may not give a good indication... so I won't consider it.
Paul
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round and round

Post by David Leikvold » Sun Apr 25, 2010 4:42 pm

Well Paul, if you'll pardon a dreadful pun, it looks like we've almost come full circle. Maybe the most realistic option is a moulded tyre with some internal metal reinforcements as previously discussed. Good luck and please let us know what happens.

Cheers
Dave
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gidge348
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Cetrifugal Acceleration

Post by gidge348 » Mon Jul 05, 2010 8:19 pm

Very interesting thread.

I was looking into solid wheels as well to get around the speed limitation problems of normal tyres. A friend of mine has a company that works with Polyurethane particularly for the mining industry. They re-cover large rollers up to 1500mm diameter and machine them down afterwards so I thought he was the one to talk to.

We did a few calculations and the forces involved are immense.

Say for instance we take your 10 inch (id) wheels rotating at 135mph and the tyres weighing say 2kg. The tyre is generating centrifugal accelerating at 14,336 m/s2 and a constant force 3.22 Tons..... that’s right TONS....
If you up the speed to say 200 mph the force becomes 7.07 TONS.....

Whatever solution you come up with for wheels and tyres just think about your tyre/wheel hanging from the roof with a good sized truck swinging from it because they are the forces we need to deal with.

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spin, spin, spin!

Post by David Leikvold » Wed Jul 14, 2010 5:57 pm

Ian, your comments about the forces involved at 135mph got me thinking. A road racing kart like the 125cc that turned up at Speedweek 2009 and ran 122mph or thereabouts runs a 5" diameter rim with a tyre that is about 9.5" diameter. The 250cc International two cylinder karts have double the horsepower of the 125cc and run a lot faster and would easily exceed 140mph at places like Phillip Island or Eastern Creek. They can do that all day with a rubber tyre that, brand new, weighs only 1.28kg on a rim that weighs 612g with bearings and valve stem (I have a 5kg electronic scale for weighing coins if anyone was wondering). So the forces acting on that tyre would be significantly higher because of the much smaller overall diameter but are obviously manageable. Without chopping up a tyre to look it seems to me that the bead wires couldn't be much thicker than clothes line wire (but obviously better quality!) and the thinnest part of the sidewall is only about 4mm thick and probably only 2 ply. But there's no denying they do the job.

Unfortunately they don't have a marked speed rating so they probably wouldn't get through scrutineering on anything but a kart. Despite that, Jack Costella uses them on his small blue Nebulous Theorem 5 lakester chasing some tiny bike engine records. I'm NOT proposing a rule change here but I think if someone was building a really small lakester or streamliner that was unlikely to ever exceed 150mph then I think road race kart tyres could be useful. Having said that, it's probably easier and less controversial to use a solid aluminium front wheel/tyre of the type Jack runs on Neb 2, 3 and 7.

Cheers
Dave :D

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Re: spin, spin, spin!

Post by psteck727 » Fri Jul 23, 2010 9:40 am

David Leikvold wrote:Ian, your comments about the forces involved at 135mph got me thinking. A road racing kart like the 125cc that turned up at Speedweek 2009 and ran 122mph or thereabouts runs a 5" diameter rim with a tyre that is about 9.5" diameter. The 250cc International two cylinder karts have double the horsepower of the 125cc and run a lot faster and would easily exceed 140mph at places like Phillip Island or Eastern Creek. They can do that all day with a rubber tyre that, brand new, weighs only 1.28kg on a rim that weighs 612g with bearings and valve stem (I have a 5kg electronic scale for weighing coins if anyone was wondering). So the forces acting on that tyre would be significantly higher because of the much smaller overall diameter but are obviously manageable. Without chopping up a tyre to look it seems to me that the bead wires couldn't be much thicker than clothes line wire (but obviously better quality!) and the thinnest part of the sidewall is only about 4mm thick and probably only 2 ply. But there's no denying they do the job.

Unfortunately they don't have a marked speed rating so they probably wouldn't get through scrutineering on anything but a kart. Despite that, Jack Costella uses them on his small blue Nebulous Theorem 5 lakester chasing some tiny bike engine records. I'm NOT proposing a rule change here but I think if someone was building a really small lakester or streamliner that was unlikely to ever exceed 150mph then I think road race kart tyres could be useful. Having said that, it's probably easier and less controversial to use a solid aluminium front wheel/tyre of the type Jack runs on Neb 2, 3 and 7.

Cheers
Dave :D

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