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Old 12-18-2007, 09:40 PM   #16
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Are you running rubber tires?
Ummmmm good question. What do you reckon? Probably was gonna run foamies. But never thought of that, what would you reckon is best? Cheers
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Old 12-18-2007, 09:43 PM   #17
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Is there anything on the net or that I can download that will tell me an estimate speed? If I put in all the details? Cheers
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Old 12-18-2007, 09:46 PM   #18
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I was going to find the roll out. If you're running rubber, no brainer. If it's going to be foams, measure them and get back to us.
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Old 12-18-2007, 09:48 PM   #19
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I was going to find the roll out. If you're running rubber, no brainer. If it's going to be foams, measure them and get back to us.
I have a brand new set of foamies. 63mm I have measured. Does that sound about right? Cheers
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Old 12-18-2007, 09:49 PM   #20
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My dad once took his x-ray 1/12 tc and put a 3.5 bl motor in it and ran it on a 2s lipo. It hit 63mph (~102kph). No damage to the motor or speedo or battery. I don't see any reason why you shouldn't be able to hit your speed mark, and I don't think you will need that much gear either. Running my bj4 with a 12x2 I hit about 38mph (~60kph) at the end of our 30m straight.
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Old 12-18-2007, 09:52 PM   #21
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My dad once took his x-ray 1/12 tc and put a 3.5 bl motor in it and ran it on a 2s lipo. It hit 63mph (~102kph). No damage to the motor or speedo or battery. I don't see any reason why you shouldn't be able to hit your speed mark, and I don't think you will need that much gear either. Running my bj4 with a 12x2 I hit about 38mph (~60kph) at the end of our 30m straight.
Do you know what gears he was using? Teeth wise?
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Old 12-18-2007, 09:54 PM   #22
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No, unfortunately I don't. I can call him tomorrow and ask though.
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Old 12-18-2007, 09:58 PM   #23
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No, unfortunately I don't. I can call him tomorrow and ask though.
Oh that would help. But you don't need to go to too much trouble. Thanks anyway though
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Old 12-18-2007, 10:02 PM   #24
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I think the RPM on my engine is about 45k. Does that sound about right to anyone? Here is a Speed calculator I found, so I need the RPM to test speed, lol.
Calculator: http://www.rcracing.com/Page.cfm?InfoID=1100
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Old 12-18-2007, 10:08 PM   #25
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I didn't use the chart, but did some math and figuring in about 30% loss from drag and efficiency, I guesstimate about a 6.00 fdr with rubber tires.

EDIT: No the rpm doesn't sound right. The 3.5bl from Novak is 10,500kv, which would be 73,500 rpms at 7v. And that motor is supposed to be comparable to a 6-7t brushed motor.
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Old 12-18-2007, 10:08 PM   #26
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I was going to find the roll out. If you're running rubber, no brainer. If it's going to be foams, measure them and get back to us.
Hi Doodad, Just wondering if you managed to find a rollout? Cheers
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Old 12-18-2007, 10:10 PM   #27
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O.K. If my math is correct, 25/69 will put you at a 1.735 (40.4mm) roll out. Once again, if my math is correct, that's more than double the RO you would want to keep that 6x1 healthy.
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Old 12-18-2007, 10:15 PM   #28
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O.K. If my math is correct, 25/69 will put you at a 1.735 (40.4mm) roll out. Once again, if my math is correct, that's more than double the RO you would want to keep that 6x1 healthy.
Ok, Would a 25/69 ratio be OK on the motor? That would get me about 70-80km/h yeh? Cheers, thanks again guys for your help
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Old 12-18-2007, 10:20 PM   #29
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I know the touring cars at indoor tracks (with foam tires around 56mm) hit 65-70 kph on a 90 foot straightaway without damaging the motors, 7x1 usually (pre-brushless). Overall final drive ratio about 10 to 1. Not sure what your internal ratio is, I think about 1.7:1. If this is correct, then you would need about a 3.5 spur to pinion ratio to get to an overall final drive of 6to 1 to let you hit 100kph.. Since your tires are bigger, you need to gear down a little more, though, around 10-12%. Soooo, this works out to about 3.9 to 4.0 spur to pinion ratio, or maybe 70 spur/18 pinion. If your internal ratio is different, you can adjust accordingly.

So, that's where I would start and not be too worried about blowing up the car. Even if it's a little slow, you can always gear up!

Sounds like fun!!! Good luck.
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Old 12-18-2007, 10:24 PM   #30
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No. It might hit some crazy speeds but will be letting out the magic smoke in no time.
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