gear selection

[jeremykent]

I have a customers cart that he wants to speed up. Just put in 6 new t-105 batteries, he already has a altrax DCX400 PDS controller and 4 ga wire stock motor 73445G02 which I believe is 2.25 HP @ 2565 RPM. Cart runs right at 20 MPH with 22'' tires. I cant decide if I want to install 6:1 or 8:1 gears (customer left it up to me to decide). The cart is normally driven on the streets or some trails but not very hilly been we are in North Florida. Just looking for anyone who has done gear changes and there opinion. I put the 8:1 in a bigblock conversion because I thought I would lose torque but it would still almost pull the front tires so not too sure on the electric?

[rib33024]

8:1 gears in a 36v cart with 22" tires you are going to lose alot of torque. you will get alot more top end. A 36v cart is nothing like a 18 hp big block for torque

[JohnnieB]

Originally Posted by jeremykent

I have a customers cart that he wants to speed up. Just put in 6 new t-105 batteries, he already has a altrax DCX400 PDS controller and 4 ga wire stock motor 73445G02 which I believe is 2.25 HP @ 2565 RPM. Cart runs right at 20 MPH with 22'' tires. I cant decide if I want to install 6:1 or 8:1 gears (customer left it up to me to decide). The cart is normally driven on the streets or some trails but not very hilly been we are in North Florida. Just looking for anyone who has done gear changes and there opinion. I put the 8:1 in a bigblock conversion because I thought I would lose torque but it would still almost pull the front tires so not too sure on the electric?

A 734454GO2 is a PDS motor, so is it safe to assume it is a PDS cart?
If so, with a DCX400 and stock height (18") tire it will have a top speed of about 24 MPH at 36V.
With 22" tire, the tops speed will approach 29 MPH.

Since the cart is only doing about 20 MPH with 22" tires, I suspect the tires are the low pressure type (Max inflation pressure 10 PSI or less), which take a lot of torque to turn and the motor cannot develop the needed torque above about 3,800 RPM.

The torque where rubber meets road has already been decreased by 18% by the 22" tires and installing 8:1 or 6:1 gears will reduce the torque at the axle by an additional 36% or 52% respectively, for either 54% or 70% total torque loss, so the cart is very likely to go slower with a gear change, rather than faster.

However, a higher torque motor and/or a higher pack voltage will increase the speed.

What top speed is the customer look for and what kind of terrain is the cart driven on?

[jeremykent]

The cart is mostly street driven some woods trails. Not really looking for a specific speed just faster than what it is.

[JohnnieB]

Originally Posted by jeremykent

The cart is mostly street driven some woods trails. Not really looking for a specific speed just faster than what it is.

With a DCX400, 22" tires, 12.44:1 gears and a stock PDS motor, the cart already has the potential of doing a sustainable 29.3 MPH on a level pavement, so something is holding it back.

It could be something simple like the DCX400 is not programmed for maximum speed, or has the wrong field map installed.

Or it could be the batteries are not being fully charged, or the high current cables, contacts and connections have excessive resistance in them.

However, I suspect low pressure off-road tires are installed rather than high pressure off-road tires.

[jeremykent]

OK the batteries are new but were not fresh charged at the time I drove the cart, so if I top off the batteries and put some extra air in the tires I should see an improvement? All the cables are clean and in very good condition. I know appearance isn't everything but I think I am good there.

[JohnnieB]

Fully charged batteries and overinflated tires will likely show some improvement.