Top Speed with high speed gear and D&D Torque Motor

[benjylafond]

What kind of top speed could I expect if I switch to a D&D torque motor (170-002-0001) from my D&D high speed motor (170-006-0001)? Specs are as follows:

TXT Series cart - 48v
6:1 gears.
20.5 inch tires
500 Amp Alltrax
HD/SD everything
00 Gauge wires.

Current top end about 34 mph.

[scottyb]

Death speed.

[Yamahaman]

Originally Posted by scottyb

Death speed.

^ ^ What he said

[gornoman]

I disagree. All things remaining equal if he switches from his high speed motor to a torque motor he will infact slow down. Am I missing something here?

[JohnnieB]

The combination of 20.5" tire height and 6:1 gears is costing you about 58% of the torque the motor puts out and the 170-006-0001 puts out 15% less than stock torque for a total of 73%

Going from 36V to 48V did increase torque by 33%, so you are down by 40%
Going from a 275A controller to a 500A controller did increase the low end torque by about 80%, but that low end torque doesn't effect top speed.

The 170-002-0001 puts out 10% more torque than stock, so the net gain going from -15% to +10% is 25%, so you would be at about 15% less than stock torque with a 170-002-0001 motor.

You might be better off with a D&D motor that puts out 20% or 40% more than stock. http://www.ddmotorsystems.com/EZGO.php
The ES-52 Type has about the same speed as the 170-002-0001, but has +20% torque rater than +10%.

Then there is than 170-004-0001 with +40% torque.

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Your motor is only spinning at 3345RPM at 34MPH, so a high torque motor might actually make your cart go faster.

I'm not sure if they will do it, but if D&D looks up the torque your 170-006-0001 is producing at about 3345RPM and looks up that same amount of torque for other likely motor candidates, you can estimate the top speed for your cart with the other motors.

[JohnnieB]

Originally Posted by gornoman

I disagree. All things remaining equal if he switches from his high speed motor to a torque motor he will infact slow down. Am I missing something here?

The slower a motor spins, the more amps it is capable of drawing, so the max RPM for the voltage applied is the RPM at which the motor is capable of drawing the amps needed to produce an amount of torque that is equal to the mechanical load.

His cart has a huge mechanical load and his high-speed motor is only spinning at 3.4k, which is more or less the middle to upper middle of the cart motor RPM spectrum, so a high-torque motor might actually up his top speed.

The difference between a high-torque motor and a high-speed motor is the amount of torque at the RPM extremes, so some high torque motors may produce more torque at a higher mid-range RPM than a high-speed motor.

We would have to get our hands on the Torque vs RPM curves of the motors to find out for sure, but I'm pretty sure the possibility exists.

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However, you are correct that in most applications, a high-torque motor is slower than a high-speed motor.

What throws the curve is that the final drive ratio of his cart is not allowing his high-speed motor to function as a high speed motor.

[scottyb]

Originally Posted by gornoman

I disagree. All things remaining equal if he switches from his high speed motor to a torque motor he will infact slow down. Am I missing something here?

In Fact no! Some of us are reading this post backwards.

[gornoman]

Originally Posted by JohnnieB

The slower a motor spins, the more amps it is capable of drawing, so the max RPM for the voltage applied is the RPM at which the motor is capable of drawing the amps needed to produce an amount of torque that is equal to the mechanical load.

His cart has a huge mechanical load and his high-speed motor is only spinning at 3.4k, which is more or less the middle to upper middle of the cart motor RPM spectrum, so a high-torque motor might actually up his top speed.

The difference between a high-torque motor and a high-speed motor is the amount of torque at the RPM extremes, so some high torque motors may produce more torque at a higher mid-range RPM than a high-speed motor.

We would have to get our hands on the Torque vs RPM curves of the motors to find out for sure, but I'm pretty sure the possibility exists.

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However, you are correct that in most applications, a high-torque motor is slower than a high-speed motor.

What throws the curve is that the final drive ratio of his cart is not allowing his high-speed motor to function as a high speed motor.

Spot-on explanations, as always.

[gornoman]

Originally Posted by gornoman

I disagree. All things remaining equal if he switches from his high speed motor to a torque motor he will infact slow down. Am I missing something here?

Originally Posted by scottyb

In Fact no! Some of us are reading this post backwards.

Oh, snap. Now nobody's right, LOL!

[benjylafond]

That cleared things up!

E-mailed engineering at D&D to get their take on it. Will post their reply.