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Old 09-22-2003, 04:14 PM   #61
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final drive i,ve never used roll out !
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Old 09-22-2003, 04:25 PM   #62
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I think you have it backwards. Your final drive ratio is built into the car. You generally cant change that without chaging size of the pullies etc.

Pinion, divided into the spur, times the final drive ratio = rollout
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Old 09-22-2003, 04:34 PM   #63
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You guys!

Spur divided by Pinion x final drive = overall ratio

This is what I believe we were both referring to.

I never use roll out/mm per rev to work out my gearing - that's best left to those who race on foam tyres or use pan cars.

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Old 09-22-2003, 05:18 PM   #64
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yeah... overall ratio... that would actually be (#of motor turns) : (rotations of the axle)

7.02 : 1 etc.... I guess your rollout would also have to include the outer diameter of your tires.
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Old 09-22-2003, 05:45 PM   #65
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Speedxl - what chassis do you run your MVP in? I'm glad you reckon my 1:8.18 is alright, cos I'd always wished I could go up a tooth or two, but never could with the TC3. Not unless I had a fire extinguisher nearby In the SD, I have no choice but to run a higher ratio (at least with the standard spur at any rate) as the smallest pinion that can be used with the Spur is 24 teeth. I'm hoping that with the 'tweaks' you have suggested, combined with the more open design of the chassis, I might just get away with it.
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Old 09-23-2003, 12:26 AM   #66
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HUH? nahh wait a sec. These are the right formulas.

Internal gear ratio - Ratio of the pulley's/gears (large/small)

External gear ratio - spur/pinion

Final drive ratio - Internal x External

Rollout - (Diameter x 3.14) / final ratio
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Old 09-23-2003, 12:51 AM   #67
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For rollout I usually run about a 29 to a 30 for medium sized track and I've run up to 33 on a large track though. (I run foams).

FDR's I normally run 6.5 on medium sized track but I've gone down to 5.84 on a large track.

My motor prep is pretty basic, standard stuff. I run reedy 767's with the standard springs(a little tension taken off the neg), polish bushings, shim correctely and all the rest...cut..sand...blah...blah... I break my motor in with the trim on my radio becuase it's alot easier to regulate the power then just wacking it on a 4 cell. For every 1/1000th taken off the comm in a cut you need to add 200sec's onto the break-in time. Motor setup is a personal thing so to anybody else this kind of setup may feel like crap. I've found that even with the serrations gone motor performance is still good.

Last edited by fatdoggy; 09-23-2003 at 12:58 AM.
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Old 09-23-2003, 07:44 AM   #68
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Have any of you guys got any idea how to get the 'new' type stock orion cores to run a little cooler? I was impressed by the motors speed during the first 2 or 3 minutes, then it went soft and needed to be rebuilt - this was on the same gearing as on the MVP

I have since cleaned it, skimmed it & replaced the brushes with reedy stock serrated items but haven't raced it again. If I can stop the damn thing from going nuclear, it might last a whole race next time

I know this is an MVP thread, but what the hell - it's worth a try
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Old 09-23-2003, 08:27 AM   #69
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horatio - the core uses an mvp arm, so you're in the right thread. the core can has some different geometry and magnets, but i've measured the magnetic field to be similar. i've also run a core, and liked it better than the mvp. when things were right, it was ok, but it was always H-O-T. i dont' think that there is a solution aside from icing it before your heats.

have any of you tried big jim's cut brushes for the mvp? i've got two sets, and i didn't notice much difference. i still have a new pair if any of you are interested. i'll mail them over to you.

lmk.

lata. oh yeah, i owe you guys some #'s yet right? coming...
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Old 09-23-2003, 08:42 AM   #70
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Gearing Question for MVP?

Where is the ideal external or final drive ratio for the MVP? I am running a EVO2 with 1.77 pullies. I am currentlly running only the Monster Stocks. Geared at 128/32, 7.08 final. The motor comes off the track at about 130 degrees. I have a couple MVPs that I got when they first came out and have not ran them due to the fact they get overly hot. I figured I would give them another shot.

Later,
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Old 09-23-2003, 12:01 PM   #71
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horatio i run a tc3. with a 100 spur and pinions between 28 thru 31 on regular size tracks!
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Old 09-24-2003, 07:58 AM   #72
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well, i did get some time to play in the oven last night. i did not estimate that the change in length, when a motor is heated to normal racing conditions, would be measureable with calibers. for this reason i built up an mvp with a metal washer at the bottom and the fiber washer atop. accidentally, this created a motor with about .001-.002 of slop. perfect! i figure that instead of measuring the change, i would try to qauge it by straight feel, by rocking the arm back and forth at different temperatures. of course, it would not rock at all if it grew more than .002.

well, using a thermocoulple in the oven, i let it soak for some time until i was confident that the entire motor was at temperature, about 300*F. i then removed the motor from the oven, and immediately tried to move the arm axially to gauge slop...

... it was still present in the same quantity as at ambient or perhaps more. i couldn't tell. just a small tic/tac back and forth. as the can cooled, i repeatedly reached over to check it at random temperatures between 300F and 70F. felt identical at all times.

if the arm grew .001-.0015 as in theory it should, i believe that the can and enbell assembly matched, or exceeded it removing all possibility of binding at elevated temperatures.

unfortunately i did not take any overall measurements of any of the aforementioned components. not smart. although it would not have changed the out come, it would have been nice data. i may need to do it again with better records.

infact, i may have to start with a frozen motor to further widen the window of temperature that i test over.

more to come...

by the way, anyone want a used mvp?
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Old 09-25-2003, 11:21 AM   #73
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seaball what you proved is now a sound experiment which further fortifies my belief that if the arm were to grow so would the can which in fact the endplay remains the same either hot or cold.
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