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Old 02-22-2009, 04:43 PM   #1
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Default Losi Excellorin 17.5T average performance?

Hi All,

Im helping a friend out who owns a Great Vigor 1/10th on-road electric.

He bought the car a few weeks back and I installed an old Trinity 27T brushed motor, and decent NiMh battery pack. There was a decent performance improvment. But it wasnt long before he was wanting more. So I suggested that we look into brushless ESC and motor.

Last week he went to the LHS and purchased a Losi Excellorin 17.5T motor and ESC combo.

I installed the motor and ESC on Saturday, using his existing pinion (24teeth). After a quick test run, it was obvious that there was little improvment in performance over the 27T Trinity.

So I plugged the ESC into the laptop and checked that all the settings were OK. Then swapped out the Tamiya plugs for Deans plugs, and re-soldered a couple of potentially suspect connections.

Still no great improvment.

I suspect that we will have to change the pinion gear in order to extract some decent top speeds out of the car or perhaps switch to the 10.5T Losi motor?

Can anyone give me some clues, the car is not being used in any official racing so we have no rules to comply with!
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Old 02-22-2009, 04:54 PM   #2
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17.5's are supposively equivilent to 27 turn brushed motors, so its to be expected that it has simular performance to that of the trinity.

a 10.5 would probably be far too fast, but it would be DRASTICALLY quicker than the 17.5, as would a 13.5.

Also, you may gear up on the motor (pinion gear) ALOT more than a 27 turn brushed. a 17.5 may be geared at around a 4.5 FRD, whilst a 27t brushed may be geared at around a 6 frd.

Hope this helps!

Gearing up will aid speed drastically, just keep an eye on temp.
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Old 02-22-2009, 06:01 PM   #3
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Hey thanks for the great response. You have answered a heap of questions.

Its disapointing that the LHS sold my mate an equivellant motor to what he already had when his request was to go faster. He dropped $280 on the motor and ESC only to find that the car went roughly the same speed!

He was told his existing pinion was OK to use.

I will tell him to buy a new pinion, or perhaps a few different pinions to try out. Can you perhaps tell me how many teeth pinion we should look at? The factory was a 24 tooth.

I dont understand FRD, can you point me in a direction where I can learn?
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Old 02-22-2009, 07:35 PM   #4
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FDR stands for "final drive ratio"

It is the amount of teeth on the spur gear divided by amount on the pinion multiplied by the internal transmission ratio.

So its

-Spur
( ----- ) * internal = final drive ratio
-Pinion

This is simply how many rotations the motor goes per rotation of the axle.

An FDR of 4.0 means 4 motor revolutions to 1 axle revolution.

If you don't know your vehicle's internal drive ratio, divide the amount of teeth on the differential gear/pulley by the amount of teeth on the drive gear/pulley.

If your brushed motor is older, a nicely setup 17.5 (geared properly) should probably be much faster than the 27t with alot more torque and more durability.

If all else fails, gear the motor up and watch temperature after a run.

If you can't hold your finger on the motor, its too hot and the timing or the gearing must be decreased. This gearing change should be drastic (a three to five tooth increase) from the stock pinion.
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Old 02-22-2009, 08:08 PM   #5
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Great info, thanks for your reply.

Looks like I have some work ahead of me.
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