I think I've decided to go electric. Now how to slow it down for cheap

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Vartz04

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I have a 500 watt 36v motor. Haven't bought the controller, batteries, or throttle pedal yet. My question is this:

How do I slow this motor down short of adding a jack shaft. I have a 12 tooth motor sprocket and a 60 tooth wheel sprocket. Those are sort of fixed as is. I see a couple options

1 - under volt the motor - run at either 18 or 24 V as that should cut the speed down to 1/2 or 2/3 of the 36v rpm (2500)

2 - use some other method. Need some help here with wiring correctly.

3- is there some way to limit a Hall effect throttle pedal to keep it from reaching max RPM/Voltage?

If I buy the controller can I get a 36V one regardless so I sort of future proof the cart for my kid? Any harm done if I run only 24V through it to a 36v motor?

Any help you can offer will be much appreciated. I'd like to order some parts soon
 
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Vartz04

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Yeah but this is for a kid. I need to physically block the kart from going over a certain speed.
 
wesleyb82

wesleyb82

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You might be better browsing the Modified Power Wheels forums but here are a few answers:
What is your estimated speed?
If you are using a 10" tire I calculate:
10"
2750RPM
12T/60T
16MPH
http://www.diygokarts.com/speed-calculator.html

How fast do you want it to go?

No need to use a jackshaft.
You can undervolt the motor with 24v but I would not do 18v as charging would be difficult. Throwing in 24v or 36v batteries is easy but only if your controller can support on the fly voltage changes which is rare. Most Chinese controllers are setup for 1 voltage level and changing the input voltage requires changing the controller. Not the best option. I use a 4QD Porter 5 controller which does support different voltages and is a beast for performance. Highly recommended.

You can limit the hall effect pedal which is most common in the PW world and what I would do here. We use a 1k linear potentiometer on the control wire which limits the amount of voltage the pedal supplies the controller which limits the top end. Wiring of the pot depends on the controller. I have seen some which are wired in line with the control wire then others were you have to wire inline with the pos hall wire and finally some require grounding the pot.

If you are looking for a package I sell a 24v kit which could work for any application that uses a 24v 500w motor. If you are going to use a 36v motor I can supply a 36v controller: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=131235799993
 
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Vartz04

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I looked at my motor again it's 2050 rpm not 2500 rpm so only 12 mph with those gear ratios. That should be doable I suppose. I guess we will see once it's out together I can always add a POT later
 
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drm

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The Kelly controller i used limits the max speed and current electronically and you can set the values. Buy a decent controller and you can use it on future projects. You can physically limit the throttle pedal as wheel.
 
wesleyb82

wesleyb82

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I have used Kelly too. You can change the max voltage through programming but this cannot be done on the fly unless you have a laptop with you. Also I was not impressed by the Kelly ramp up rates. If you want something with good acceleration I would not choose Kelly.
 
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Vartz04

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I'm going to start off with a cheepo. I'm not 100% convinced electric is the way to go but I'll keep kelly in mind
 
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Vartz04

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I was talking super cheap (China for $13) controller should be here next week

I'm not 100% convinced I'll like and or want to leave this thing electric so I'm willing to waste a little money should I need to upgrade it later but at least I'm not out much (and could likely flip the cheaper stuff locally pretty quick) if I decide gas is the way to go
 
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