# 48v off-road scooter build



## lazzer408 (May 18, 2008)

I have too many projects... 

Here's a scooter I'm building to test a controller on. I'm experimenting with different throttle position, voltage, and current ramps to see what gives me the feel of a gas engine. I'd test it on my Yamaha but, should something go wrong, I can't exactly hop off and push a 1200cc cruiser to the ground like I can a scooter. Plus I'm a big kid at heart. 

I started with a bank of 12x 12v 8ah batteries in 3p 4s groups for 24ah 48v. The batteries max current is 85a for 10 seconds which in 3p gets me 255a. Not sure what they sag to at 85a draw so I don't know what my peak wattage is. Say sag is 10v. I'll have 10,200kw peak to work with. The main deck/frame is steel and built sort of like an I beam. It's the lightest strongest thing I could think of out of steel. See, staring at the ceiling does have it's benefits. I got the idea from the laminated floor joists. 

The rear swing-arm is aluminum plate (wood mock-up in the pics) and the tires are ~14"x6" ATV tires. The rear shocks lay horizontally and will be 6" mountain bike shocks. Front end will be telescopic forks. 6" travel front and rear. Disc brakes front and rear. The motor is a cheap $68 series-wound 12v winch motor. I have made no modifications to the motor at this time but it will likely be rewound. It's something I can get cheap parts for and a good place to start. The motor is mounted in the swing-arm to avoid chain alignment/tension issues. It becomes a somewhat structural component and the added unsprung weight isn't much of an issue with the motor's location close to the pivot point of the swing-arm.

_A note on the motor:_
_It's built like a large starter motor. They come in both sleeve and dual ball bearing, and both 12v and 24v versions. Rated at 2.5hp but other (12v) versions can be as high as 5hp or more. This 12v one draws huge amounts of current so plan on some more windings on the fields if you can fit it. I'll know soon enough. I might even modify a starter/generator armature to be used in this housing since the SG motors use an armature with more/smaller windings yet still beefy enough to hold some amps. This motor is a 4-pole. The Yamaha/EZGO Hitachi SG is also a great 4-pole motor. I'll dig into that later._

The scooter uses a jackshaft for 2 reductions. Chain is #35. First reduction is 1.66:1 (20t/12t) and the second is a 6:1 (72t/12t). Total reduction is about 10:1. 6000rpm on the motor gets me 600rpm on the rear tire. That calculates to ~25mph which is fine and I'll have great hill-climbing torque. The first reduction is also outside the swing-arm and will be under a cover. This allows fast ratio changes. I could swap in a 16t at the jackshaft input and jump to 32mph (for example).

Thought you guys might like to see it so far.


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## Salty9 (Jul 13, 2009)

Interesting.


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## alexcrouse (Mar 16, 2009)

I plan on building something very similar, so i will be following this thread. Ill be using an AllTrax AXE 7245 controller for the initial build. Keep up the awesome work!


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## DavidDymaxion (Dec 1, 2008)

I like it! That's nice how you are doing double duty with the battery box also serving as a frame. Is the motor a strength member for the rear swingarm?


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## lazzer408 (May 18, 2008)

DavidDymaxion said:


> I like it! That's nice how you are doing double duty with the battery box also serving as a frame. Is the motor a strength member for the rear swingarm?


The bolts that hold the brush end housing on do go through the plate. It adds some strenght but the design does not depend on it. I have the sprockets, chains, and my shocks but I'm STILL waiting for my swing-arm plates from the water-jet.  My new batteries are here too.


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