Modifying my Piaggio mo-ped Part 2

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nasukaren
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Modifying my Piaggio mo-ped Part 2

Well, I went to Tractor Supply Center (TSC) today and all they had were imperial sized pulleys (1/2" and 3/4"). The motor that I have must be a metric size one because the 1/2" hub pulleys were too large. I bought some 1/2" hub pulleys anyway since I wanted to see if it would work as a proof of concept (and just around how much more power I'll need).

Now I just have to make a mount for the motor. I think I'll just use a piece of 2x6 wood that I have laying around and make a simple mount.

I took the motor, motor controller, batteries, and everything else out of the Razor. I tried to play with the motor controller. It turned out the "throttle" on the bike was only a switch and not a potentiometer. I tried using a 5K pot but the motor speed (unloaded) didn't seem to change any. I'm not sure if this controller is variable or not, but it wouldn't make any not to be, right? Maybe I need more resistance.

If I can get the pulley and V-belt on next weekend and cut the mount and drill it out, I'll be able to get the electronics in and the mo-ped on the road to test it out.

---

To answer some of the comments on the previous post:

1. Definitely 240 watts is too little, if that is the actual rating of the motor. Once I get this to work and can show proof of concept to my partner, my budget for getting a bigger motor should be approved.

2. I thought about a hub motor and might go down that route if belts/pulleys become too much of a bugaboo. It'd certainly solve a lot of problems except the financial ones -- most ones I've seen are $300-500 right? That's about $200-400 over my current budget (until I can prove that this will work, and that I haven't ruined my partner's mo-ped in the name of science).

Karen

nasukaren
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Re: Modifying my Piaggio mo-ped Part 2

p.p.s. Actually, the PowerPack motor does look ideal and could definitely serve as the replacement when I get the current motor installed.

I'm wondering if I could run the PowerPack on the 24V / 30a controller that comes with the Razor. I think the Razor motor is permanent magnet as it only has two wires coming out of it, black and red, going into the motor controller. Recycling the controller would save me $180.... and since 24 V x 30 A = 720 watts (around the rating of the PowerPack), it'd be great.....

http://powerpackmotors.com/

Thanks for the reference!

Working on a Piaggio Boxer (mo-ped) EV conversion: http://gpsy.com/ev

chas_stevenson
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Re: Modifying my Piaggio mo-ped Part 2

The PowerPack motors are brush less motors and will require a brush less controller. A standard brushed motor controller will not work. Also even a 240-watt motor will put out the 720-watts from the stock controller for a short time and if this was too small for your use then getting a bigger motor and connecting it to the same controller with the same voltage and current output will do almost nothing. The controller is the biggest factor in the equation to power a motor, of course the batteries must be capable of supplying enough current to the controller.

example:

    1. Using a 500-watt motor with a controller rated at 24-volts @ 20 amps. The motor will receive 480-watts of power no more.
    2. Using a 750-watt motor with a controller rated at 24-volts @ 20 amps. The motor will receive 480-watts of power no more.

So both motors will output very close to the same power, 480-watts. You will need to increase the voltage to increase the speed of the motor and amps to increase the power/torque of the motor. To increase runtime or range of the vehicle you must increase the Amp Hour rating of the battery pack.

Hope this helps,
Grandpa Chas S.

nasukaren
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Re: Modifying my Piaggio mo-ped Part 2

Grandpa Chas -

Thank you very much for the information!

Since the controller is rated for 30A but the motor is clearly not putting out that much power, it must be the *tiny* little 7 ah SLA batteries that came with the Razor that are the limiting factor. Once I get everything running, I'll experiment with a bigger batteries to see if that will make the motor more energetic.

The worst case scenario is that if I pump 20-30 amps into a motor rated for 10 amps (240 watts / 24 v = 10 amps, right), I'm liable to burn it out *fairly* quickly, right?

Karen

p.s. I'm hoping I don't burn it out, though since I might want to recycle it into a generator for a wind turbine. It'd be great to have totally free energy for my daily commute!

Working on a Piaggio Boxer (mo-ped) EV conversion: http://gpsy.com/ev

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Re: Modifying my Piaggio mo-ped Part 2

Karen,

You are correct in assuming you will burn the little motor applying that much current to it. One thing to note is that almost all DC motors can be pushed to over twice their rating for short periods of time but as you said if you try to run the motor this way for extended time they will burn up. I have one e-bike with a 400-watt motor which I push to 900-watts during acceleration all the time and it is on it's second year of operation. I just back off the throttle when I am up to the speed I want to travel, about 20-mph.

As for the 7-AH batteries they can put out about 50-amps with no problem so that is NOT your limiting factor. You are trying to move a lot of weight and really need about 1500-watts to do what you want with any real success. Your idea is sound but you just don't have enough power. 1500-watts might get you 20mph. The other factor is the voltage you are trying to use. 24-volts will require 62.5-amps to get to 1500-watts you would be much better off using about 60-volts (5-batteries) so the current draw would only be 25-amps for 1500-watts. The more amps you draw from the batteries the faster you will deplete and destroy them.

Grandpa Chas S.

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Re: Modifying my Piaggio mo-ped Part 2

Grandpa Chas -

Thank you so much for all of the useful information! I'm a little confused as you say that your 400 watt motor can do 20mph but then also tell me that I need 1500 watts in order to do 20 mph.....

If I can do 5 mph with this setup and show that this hasn't been a total waste of time/money/scooter, then I'll look into getting the PowerPack motor and perhaps hopping it up to 48 volts (2 batteries on each side in panniers). It's a small scooter and it's just for around town use, so I don't need that much of a range.

Working on a Piaggio Boxer (mo-ped) EV conversion: http://gpsy.com/ev

nasukaren
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Re: Modifying my Piaggio mo-ped Part 2

I was wandering around the web and found this motor:

http://www.robotmarketplace.com/products/MAG-S28-150.html

This also looks like it'd fit and the motor mount / heatsink design is neat. Too bad it's $300+ ! Maybe I can find a used one from a damaged battlebot........

Just out of curiousity, I now know that I can run a 10A motor on a 20A controller (for a short period of time), but what happens if I attach a 20A controller to a 200A motor? Will it simply just run slowly or do I risk damaging something???

Thanks!

Working on a Piaggio Boxer (mo-ped) EV conversion: http://gpsy.com/ev

mopedbrainy
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Re: Modifying my Piaggio mo-ped Part 2

motors are usually measured up in watts= mov. meter/second.One horsepower 750 watts.

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Re: Modifying my Piaggio mo-ped Part 2

Thank you so much for all of the useful information! I'm a little confused as you say that your 400 watt motor can do 20mph but then also tell me that I need 1500 watts in order to do 20 mph.....

The reason I can do 20 mph with a 400-watt motor is because my bike is much lighter than what you are trying to move and as I said I push the motor to 900-watts. It takes less power to keep something at speed than it takes to get it there.

If all you want to do is move the mo-ped 5-mph then you may be able to do this with the motor and controller you have, but you will need a very low gear ratio. If the motor turns 2500-RPM, which is about right, then you could calculate the gear ratio needed to move the mo-ped 5-mph based on the size of the drive wheel.

Grandpa Chas S.

p.s. 738-watts = 1-hp.

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Re: Modifying my Piaggio mo-ped Part 2 - the gearing

Grandpa Chas reminded me to check my gearing.

My wheels are 14" in radius, so if my high-school geometry is right, that's 2 x pi x r = 88" in circumference.

If I want to do 5 mph, that's 316800 inches per hour, that's 3600 rotations per hour or 60 rotations per minute.

My mo-ped's rear hub has a built-in 7:1 gearing reduction, and I'm hoping for another 2:1 gearing reduction using the v-belts. That gives me a 14:1 gearing reduction.

60 rpm * 14 = 840 rpm.......

Not good for keeping the tiny little motor I have in its peak performance area. I guess it's good for when I get a bigger motor since it means that without changing my gearing, I can get a good 20 mph at 3300 rpm.

All this is pointing to me getting a bigger motor.... is there anywhere that sells a 600-800 watt 24V dc motor (4" long or less) for $150?

Working on a Piaggio Boxer (mo-ped) EV conversion: http://gpsy.com/ev

chas_stevenson
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Re: Modifying my Piaggio mo-ped Part 2 - the gearing

Karen,

It appears you are smarter then a fifth grader your calculations are correct. As for a motor in you price range I know of no brushed motors however there are some high performance small motors at this link. They are all brush less. These are the only motors that I know of that are small enough yet powerful enough for your use.

Grandpa Chas S.

nasukaren
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Re: Modifying my Piaggio mo-ped Part 2 - the gearing

Grandpa Chas -

Thanks for the link! I'll check it out. If I get the Piaggio up and running (slowly) this weekend, I'll begin the pre-whining process for the approval of a more powerful motor.

This is the one that I have my eye on:

http://www.robotmarketplace.com/products/MAG-S28-150.html
3" Diameter, 4" long
1/2" diameter shaft with 1/8" keyway, 1.75" long
24V (can be run higher)
3 horsepower
1970 oz-in Torque
Max current 285 Amps

The fit is fantastic since my motor compartment is only 4" long and it has 3 horsepower! It also has a very nice optional motor mount that I plan on using. I don't think I'll be running it at anywhere near its peak specs, especially as I don't know of a controller that can handle that. Maybe I'll just run it off a solenoid....... :-P

I'm a bit concerned since it has neodymium magnets and I heard those are really heat sensitive. But since I'll be running it at rather low amps, maybe I'll be OK?

What do you think, Grandpa?

Karen

Working on a Piaggio Boxer (mo-ped) EV conversion: http://gpsy.com/ev

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Re: Modifying my Piaggio mo-ped Part 2 - the gearing

Karen,

That is quite a motor and it will run hot so the magnets will suffer as you suspected. I am not sure I would want to spend that much on a motor knowing that is may only last about a year. I know this is a lot more money but the Mars Brushless PMAC Motor is a much better choice. This motor will give you years of trouble free operation as a matter of fact it will out last the vehicle by many years. I know it a little bigger than you want but I think it would be worth modifying the scooter to accept the larger motor. The problem with smaller motors is they just don't hold up. There is a lot of strain being placed on a drive motor and this is one place you really don't want to under estimate. I know most of the motors I have shown you are brush less but they are the better choice for a DC drive. To be honest the best drive systems are AC motors but these are not only out of the price range but way to big as well.

To get back to the motor you have chosen, yes it should work just remember the 6000 rpm will need even more gearing.

Grandpa Chas S.

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