12-12-2014, 07:49 PM | #1 |
Not Yet Wild
Join Date: Sep 2011
Posts: 65
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Motor Help
Ok guys. I don't get on here often, but when I do,you help me a lot. I have a custom built '07 PDS cart. It's been converted to 48v, has Alltrax controller, 12:1 rear and 10" tires. It had a 11.8/19.5 horse 36/48v motor in it. However, while cruising through the neighborhood at 34mph, the motor melted to itself and locked down. My question is, what motor go I need to handle the rpm's? Thoughts? Thanks in advance.
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12-12-2014, 09:13 PM | #2 |
Gone Wild
Join Date: Feb 2011
Location: Chattanooga TN
Posts: 2,105
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Re: Motor Help
I'll bet the neighbor were happy.
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12-13-2014, 02:54 AM | #3 |
Over This Interview Is...
Join Date: Jun 2012
Location: AZ
Posts: 17,449
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Re: Motor Help
If you are lucky, the controller survived the "melt down".
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12-13-2014, 07:23 AM | #4 |
Not Yet Wild
Join Date: Sep 2011
Posts: 65
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Re: Motor Help
Yeah, I know. I have to get a motor first so I can check everything else. I just don't know which one to get. I was hoping someone could help and that maybe someone had a good used one for sale.
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12-13-2014, 07:25 AM | #5 | |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: Motor Help
Quote:
I've slid to a stop from about 34MPH, also. Fun isn't it? Alltrax makes different ampacity sepex controllers. Which one are you running? I suspect what you are calling 12:1 gears are actually 12.44:1 (stock) gears. I seriously doubt you have tires that are 10" tall. That is either the rim diameter, or the tire width, neither of which affect motor RPM. With the actual gear ratio and the actual tire height (Measured - Not what is embossed on the sidewall), I can tell you what the motor's RPM was at 34MPH. Basically, if your cart does in fact have 12.44:1 gears and tires are 22" or taller, your motor was spinning less than the 6500RPM max recommended RPM by many motor manufacturers, so RPM alone probably was not the sole cause of your motor failure. Heat kills electric motors and a mismatch between the motor and Field Map can generate a lot of heat throughout the RPM range. Running in Turbo mode also generates a lot of heat. If the motor failing during operation didn't take out the controller, don't buy any lottery tickets for a while, you've used up a lot of luck. |
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12-13-2014, 07:40 AM | #6 | |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: Motor Help
Quote:
Measure the voltage between B- and M-. It should be pack voltage when pedal is pushed just far enough for solenoid to click and then descend to zero as pedal is pushed to floor. You can also do a diode test. See attached. As for what motor to get: Give D&D a call and talk to Vic or Eric. Be prepared to answer some questions about cart, such as gear ratio, tire height, number of seats, terrain used on, top speed desired, pack voltage, which controller, which solenoid, gauge of high current cables, Etc. |
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12-13-2014, 07:46 AM | #7 |
Not Yet Wild
Join Date: Sep 2011
Posts: 65
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Re: Motor Help
Ok. The cart is at my old neighbors house in pieces. I'm gonna try to swing by and get the alltrax info. The tires are about stick height which I thought was 10". The gear is not stock. We've changed it several times. Does 8:1 sound right? Here's the motor.
Last edited by racinjason89; 12-13-2014 at 07:48 AM.. Reason: Picture. |
12-13-2014, 07:49 AM | #8 |
Gone Wild
Join Date: Sep 2012
Location: Savannah, GA
Posts: 2,760
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Re: Motor Help
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12-13-2014, 07:54 AM | #9 | |
Gone Wild
Join Date: Sep 2012
Location: Savannah, GA
Posts: 2,760
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Re: Motor Help
Quote:
I would be calling Eric or Vic at D&D, they can spec you a motor that will do what you want safely (within reason) and be more efficient amp wise to your battery pack. |
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12-13-2014, 08:41 AM | #10 | |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: Motor Help
Quote:
8:1 and 6:1 are used for higher speed. Push the cart and count the number of times the input shaft on the differential rotates for each revolution of the tires. With 18" tires and 8:1 gears, the motor spins at 5,079RPM at 34MPH and the torque loss is 36% With 18" tires and 6:1 gears, the motor spins at 3,810RPM at 34MPH and the torque loss is 52% In either case, RPM isn't an issue, it is the torque loss. In a nutshell, with 8:1 (or taller gears), and stock height tires, you are not very likely to spin the motor fast enough to harm it, since 6500RPM will propel the cart at about 44MPH (or faster). On the other hand, due to the torque loss in the gearing, the motor has to produce more torque to move the cart and more torque equates to more heat. The motor pictured appears to be D&D blue. What model was it? If it was wound for high speed, you created a perfect storm. You need a high torque motor to turn tall gears (or tall tires) Basically, the motor should match the final drive ratio (Gear ratio plus tire height), the Field map should match the motor, the controller ampacity should match the motor & final drive ratio needs, and the battery pack & cables & solenoid should match the amp needs of the motor. FWIW: TerryH uses the same motor I use on his modified PDS with 6:1 gears. (Not the dragster - the street machine.) Last edited by JohnnieB; 12-13-2014 at 08:45 AM.. Reason: Added comment |
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