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12-28-2016, 02:00 PM | #1 |
Not Yet Wild
Join Date: Oct 2016
Posts: 55
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Questions about speed and over-revving
I've got a new SR48500 controller, new 4ga wires, and a fresh Bandit motor on my 98 TXT cart. The cart has a lift and 22" tires and does really well in sketchy off road conditions.
On flat gravel or road, I'm curious how fast a cart like this should go with fresh batteries at 36v. Also considering all the warnings from Plum Quick, what would be considered over-revving? It doesn't take much to get this cart up to 20 mph on a slight downhill and it probably does 10-12mph on flat-ish ground. |
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12-28-2016, 02:54 PM | #2 |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: Questions about speed and over-revving
The specs for a stock TXT with 36V series drive on stock height tires (18"), is 12-14 MPH. With 22" tire, the theoretical top speed is 17.1 MPH, but it won't go that fast because the taller tires reducing the torque where rubber meets road by 18%. Maybe 16 or 16.5 MPH, unless the tires are the low pressure type. Then the speed will be even less due to the increased rolling resistance.
The Bandit motor is supposed to up the cart's speed, so you may get 20 MPH, maybe more. 20 MPH on 22" tires is 3800RPM at the motor, which is within the normal operating RPM for any golf cart motor. A conservative max RPM for most cart motors is 6000RPM, which is 31.5 MPH on 22" tires and 12.44:1 gears in the differential. |
12-29-2016, 03:45 PM | #3 |
Not Yet Wild
Join Date: Oct 2016
Posts: 55
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Re: Questions about speed and over-revving
Ok thanks. Sounds like I don't really have to worry about over-revving. These tires are only supposed to be pumped up to 5 psi. Think that's why I'm only getting 10-12mph on flat ground? The brakes don't appear to be dragging and I've got brand new bearings in the front wheels. Trying to figure out why this cart would be going this slow with basically brand new everything except the rear axle, wheels, and tires.
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12-29-2016, 03:57 PM | #4 |
Gone Wild
Join Date: Jun 2014
Location: Brandon MS
Posts: 309
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Re: Questions about speed and over-revving
I had my low pressure tires set on 15 psi. The ride at deer camp was very harsh. Lowered them to 10psi. Much better ride. Good compromise between comfort and speed/rolling resistance.
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12-30-2016, 10:59 AM | #5 | |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: Questions about speed and over-revving
Quote:
With the low pressure tires you have, I'd be more concerned about motor heat. The hotter a motor runs, the less its lifespan and the tire height/tire type combination you are running has the makings of a motor running hotter than normal. A PQ Bandit has more torque/speed than a stock motor, but it is still in a stock sized housing, so more power is being generated in the same sized container while the heat dissipation abilities remain the same. The low pressure type tires are very likely why your cart's top speed on level ground is less than what a completely stock cart's top speed is on level ground when it ought to be about 22% fast with 22" tall tires. There is the possibility your controller's PWM output isn't reaching a 100% duty cycle for some reason. That can be checked with two voltage measurements. 1. What is the battery pack voltage while cart is traveling at top speed on level ground? 2. What is the voltage between the controller's M- and B+ terminals while cart is traveling at top speed on the same stretch of level ground? The SR48500 drops 0.18V per 100A flowing through it, so the voltage between M- and B+ ought to be <1.0V less than the battery pack voltage while at top speed if the PWM output is at 100% duty cycle (wide open). |
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01-02-2017, 06:20 PM | #6 | |
Not Yet Wild
Join Date: Oct 2016
Posts: 55
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Re: Questions about speed and over-revving
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01-03-2017, 09:19 AM | #7 | |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: Questions about speed and over-revving
Quote:
That points to the low pressure tires holding the speed down. ----------- I have a problem finding level ground here also. |
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01-03-2017, 06:19 PM | #8 | |
Not Yet Wild
Join Date: Oct 2016
Posts: 55
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Re: Questions about speed and over-revving
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