2.2" foams with 12mm hex?

[cool head]

i started my car today. my problem is gearing. with all the gears availble, i can only hit 106mph. my only option is to use 2.2" foams with 12mm hex. does anyone know where to find some. i found some jaco's but there for rc10gt and don't know if they use 12mm hex. any clues?

also, can anyone give me tire circumfrance of the hpi super nitro belted slicks?

thanx all

[nitro13]

HPI Super-Size Racing Slick Tires

Outside Diameter: 2.9" (74mm)
Inner Diameter: 2.2" (57mm)
Width: 1.4" (35mm)

is this the info you need

nitro13,

[cool head]

no, i need someone to take a tape measurer and measure the circumfrace of the tire. i can multiply 74mm by 3.14, but i dont trust that method. i would like actual tape readings if anyone can give them.

thanx anyway

i'm also in the market for a 32p clutch bell bigger than a 18, anyone?

[rcguy2477]

According to the mathmatical way, it would be very close to 232.4778564..... If the measurement of the diameter was accurate, this should be accurate also.

[racerrandy]

http://www.dirtoval.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=10;t=000020
Check this out, he makes these for gt,losi, and some others I think. They use ntc3 spin on spurs that go up to 27 tooth.
Also Mugen gas trucks use wheels that have a 12mm hex I believe, but if you are using them on a touring car the axle on the car isn't long enough to screw the wheel nut on. You could put foams on a SNrs4 wheel though. I think the belted hpi slicks might be the way to go to me. I am not sure foams will stay together, but I don't know this for sure.

[DCLXVI]

Wouldn't it be possible to mount the truck axles on the tourer? All that would be needed (worst case) are new bearings with larger inner diamter...?

[thefasttrack]

your problem is not gearing or the tire you also have to think of friction (hint bearings) i have had a run of 90 so far but my beraings keep breaking so think of the little things first than the big things because thwe little thing cause big problems if there not delt with i have totaled 3 cars so far because of bearing.

[cool head]

i've got good bearings(boca). the larger tires will releave a lot of stress on the bearings. thats why i want to use 2.2. i could use ofna 1/8 buggy foams. but i'm thinking too much weight.

[thefasttrack]

ahhh ididnt think of that at all good call ^ ;)

[modellor]

The question is, can foams withstand the forces that will be applied to them at speeds over 100mph????? :confused:

We know they can withstand speeds off around 90mph but chunking occurs at the slightest knock. What would happen when we go over 130mph which will most probably be the case? :eek:

[cool head]

well i chucked an old 1/10 foam to my die grinder. that spins at 10,000rpm. it held together, so i'm gonna imagine that they'll hold together at 6-8k rpm. not really a whole lot of tire options. the only other option is to use the belted super nitro tires. i'll have to do the die grinder test on one of those.

[DaFF]

Coolhead,

A 1/10 sedan foam tire spinning @ 10 000 rpm only translate into:

Outside diametre of 1/10 sedan tire = 60 millimeter = 0.06 meter

Perimeter of a 1/10 sedan tire = Pi x OD = 0.1885 meter

Thus a 1/10 sedan tire rotating at 10 000 rotation par minutes will be equivalent at moving the 1/10 sedan as :

0.1885 x 10 000 = 1884.95 meter par minute wich translate into

1.88495 kilometer per minute, that's 113 kph or 70.68 mph !!!!

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At 120 mph ( 192 kph ), a 1/10 sedan tire will spin roughly @ 17 000 rpm :D :D :D

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So, to be conservative, you need to spin the 1/10 sedan @ 20 000 rpm....

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You better have it extremly well balanced if you don't want it to blow in your face....

Most ppl don't realise how hard it is to reach those speed LoL

Only my 0.02 Euro

DFF

[DCLXVI]

Put it in the dremel...then you can test it @ 33 000 rpm :D

[cool head]

i'm gonna end up using 1/8 buggy foams. the circumfrance measures 12.5 inches. that will give me some leeway on clutch bells and my top speed as well. with my gear ratio i'll end up with an final drive output of13,000 rpmX12.5=13,541fpm=apx154mph. i've got a faster dye grinder at work that willl hit 15k rpm, i'll try that and see how it goes.

[traxxas-dude]

Put it in the dremel...then you can test it @ 33 000 rpm :D

My Dremel hits 35K :p

Or you could find a way to hook one up to a stock motor or something...

[StevePond]

Boy, I wouldn't want to be anywhere near a Dremel with a wheel chucked up and running up to 35K. That's a recipe for disaster. ;)

[YR4Dude]

Guys,

Did it ever occur that those foam tires at these tremendous speeds are going to expand like crazy?? So far the only people (Cliff & Steve, etc) who have done successful speed runs have used only a certain kind of tire thats been known to work in high-speed applications and that has to be CAPS. In regards to finding a large wheel with a 12mm hex, the new Proline wheels are a likely possibility. Get a set of those and shave off the rim edges and send them to BSR to have belted caps mounted to it and you might have a tire that will work for your grear ratio.

This is just a thought, unless there's another better solution for tires, this may be more an exploding tire contest rather than a speed contest.

[racerrandy]

This run wasn't in the guinnes book but Chris Collins ran 112 mph in 300' using foam tires.
Steve Pond used kevlar belted tires not caps.
Cliff Lett used caps on his l30, but used yok belted tires on his tc3.
Later,Randy

[DaFF]

Most model dragster run on foam and are going close to 100 mph with a lot of stress on the tire due to the heavy accel. It doesn't seems to be a problem.

DFF