PDS cart w/500A alltrax, gear change or motor upgrade?

[sportcoupe]

I'm picking up a stock pds cart today and will install an Alltrax DCX500PDS controller package from scottyb along with 2 gauge cables. I intend on staying with stock height tires and 36v. I want a street screamer, no hills in my area at all.

I want much more speed then the controller alone can deliver. Would I be better off with high speed gears (6:1?), (8:1?), or an aftermarket performance motor keeping stock 12:1 gears?

[scottyb]

The 36v cart will 'scream along' at 24 mph. For more speed it's best to add voltage first. Then consider some of the items you have listed

[sportcoupe]

24 mph is slow. I've already built a 48v pds with 23" tires and it ran 31 mph using the same alltrax and stock motor.

I'm looking for 35+ mph with stock size tires at 36v. Would I be better off with 6:1 gears or an aftermarket hs motor?

ScottyB, I'll be calling you later today for another 909 package once I have the cart in my hands.

EDIT: I checked the speed calculator and with 18.7" tires at 35mph the motor would be spinning 7800 rpm. I think I just answered my own question, gears are needed to obtain those speeds with stock size tires.

[JohnnieB]

Just curious, what make & model tires are 18.7" tall?

Anyway, at 35MPH with 18.7" tires, the motor would spin at about 5,000RPM with 8:1 gears and about 3,800 with 6:1 gears.

Personally, I'd go with the 8:1 to keep the motor temperature down.

Also, upping the pack voltage will reduce number of amps flowing for the same power input to motor, which in turn will reduce the resulting motor temperature rise.

[sportcoupe]

215/40-12 tires are 18.7" tall on average. Ebay has them shipped for good price.
http://www.ebay.com/itm/Duro-Excel-2...61ea18&vxp=mtr

I figured 8:1 would be better then 6:1 but I don't know if it'll give me 35 mph at 36v. I don't want 48v, did that with 23" tires and motor ran pretty warm (195°F).

I don't know if 6:1 gears and stock height tires would allow the motor to run cooler then 48v and 23" tires using 12:1 gears.

[JohnnieB]

Measure the tires when you get them.

An Alltrax DCX controller is supposed to give you 24MPH on stock height (18") tires, which would be 5,575RPM at the motor.
Mathematically, with 8:1 gears and 18" tires, the cart should go 37.3MPH at 5,572RPM.
With a 500A controller and a health set of batteries, I suspect you'd get 35MPH or mighty close to it at 36V.

The thingy about motor temperature is based on the fact that heat increases exponentially with current flow (I^2 = W) while power is also directly proportional to volts (I * E = W).

If the load remains constant, it takes the same number of Watts to move the cart at the same speed from Point-A to Point-B at 36V as it does at 48V.
Lets say it takes 2000W.
With a 36V system, the average current flow would be 55.5A.
With a 48V system, the average current flow would be 41.6A.

In this example, every Ohm of impedance in the motor will convert 193.2 more Watts to heat in a 36V system than in a 48V system.


----------
Food for thought.
I'm kicking around the idea of using the motor's speed sensor to run a tachometer.
I piggybacked the tachometer function of one of my DMM's to the sensor output and it worked measured the RPM accurately in the 8 cylinder mode.
The PDS controller feeds the sensor with 14V, so I'm pretty sure feeding it from a 12V battery would work.
IIRC, the old tachometers I used during my hot-rod days, connected into the coil's primary wire, so one of them might work.
Then I'll be able to calculate cart speed when I don't Have a GPS with me.

Also, the Ex-Ray system uses a pulse from a magnetic sensor and if the tires circumference was divided by eight, it should read the correct cart speed based on motor RPM.

[sportcoupe]

I certainly will measure the tires, I know they can be up to 1/2" shorter then spec. Alternately I could order 215/35-14's, they spec at 19.9" tall. No lift required either.

quote:
"Mathematically, with 8:1 gears and 18" tires, the cart should go 37.3MPH at 5,572RPM"

That's interesting. No expanding on that with 6:1 gears and 18" tires, the cart should go ~47MPH at 5,572RPM. Of course the motor probably doesn't have the power to obtain those speeds more then likely and I'd hit a wall somewhere around 40 I'd say.

Things could be getting very interesting around here soon. Now I have to ask myself do I want to settle for 8:1 gears when the 6:1 are about $10 more? Whats the worst that could happen?

[Sir Nuke]

OR get the gears AND a high speed motor and REALLY fly!! LOL

[sportcoupe]

The Alltrax DCX500 and 6:1 gears have been ordered today. Going for max and see what happens.

[JohnnieB]

Originally Posted by sportcoupe

The Alltrax DCX500 and 6:1 gears have been ordered today. Going for max and see what happens.

My spreadsheet says 49.8MPH with 18" tires and 6:1 gears.
I suspect you are right about running out of power before you get that fast.
It will be interesting.