[GT550] Extended Swingarm?

[Frank]

Hi Guys,

I've been drag racing my old GT550 (electric conversion) and am at the point where I need to either add a wheelie bar or extend the swingarm. I'm open to suggestions, advice, etc. It doesn't look that hard to extend the stocker but I'm curious what others have done.

thanks,
Frank

[Vintageman]

Not sure if it fits but a Suz t500 may be longer.

What are you running for E motor and Drive?

[Frank]

T500 is longer by a couple of inches but narrower. I'm thinking I need to buy a spare online and make my own extension. I think 4-6" would make a noticeable difference.

I'm running an ADC 6.7" motor, Z1K controller with 72S2P LiPo 100C cells. The pack weighs 53# and can make 250hp for about a minute. After the rider the weak link is the motor. I'm having a blast! The only track in Maine is about an hour from my house (1/8-mile). At ~60% power I've run a best of 7.6/89 mph. I'm working on my starts which are hampered by wheelies and wheelspin. Ultimately I think I'll be mid-6's/100+ mph. The bike is about 100# lighter than stock.

[Vintageman]

Yes narrow sorry. I have both bikes and t500 is skinnier.


I did a quick look see at your set up. Wow those LiPo can discharge quick. But 250HP peak

so you have 72*3.7V = 266V to motor

250HP at 746 Watts per hp = 186500 Watts / 266V = 700 Amps!

Is there more than one model of the motor ADC 6.7"?

E motors have a lot of power/torque, but a gal gas has a lot of energy too. But dang you can get the batts to discharge so fast

fun stuff

[Frank]

I have a T500 also, that's how I knew. (Actually more than one, lol.)

Your analysis is pretty good but you overlooked the role of the controller. It's job is to essentially send current to the motor (as a function of throttle position) but with certain provisos.

There are several varieties of the ADC motor (I hope this isn't too boring btw), I have a "smaller" one with 4 brushes; others have 8 brushes, which means 50% more brush area. KillaCycle uses two such motors. My current setup is 750A/150V which puts a fair load on this small brushed motor. If I command full throttle the controller sends 750A to the motor but because the motor has extremely low resistance, this only takes a few volts. As it starts turning it also acts as a generator and generates a voltage that opposes the controller voltage (the so-called "back electromotive force"). The controller continues to increase motor voltage to maintain 750A until it either hits the programmed limit (150V) or until the battery pack sags to less than 150V.

Still with me? The batteries are 4.5 amp-hours with two in parallel for 9AH. 100C means this pack can output 900A! 3.7v is "nominal" but they can safely be charged to 4.2V. I'm actually using 4.0 so hot off the charger the pack sits at 288V. The controller "trades" voltage for current so battery current actually starts off quite low (Ex. 750A * 10V at the motor is 288V * 26A at the battery, i.e. constant power). A single run down the strip uses very little energy and I recharge very quickly.

You are correct, a gallon of gasoline has a LOT of energy (30-32 kwh) but most of it gets wasted as heat or goes out the exhaust. Before making this bike into a racer I used it to commute with different motor, controller and batteries. 32 kwh would have taken me about 250 miles!

Sorry for the long post but this stuff is every bit as fascinating to me as carburetors, expansion pipes and cylinder porting.

[Vintageman]

Yes when a motor is not turning no back emf. So all current but little voltage ( so V*I is low). So you have a heck! of a lot of torque (what's nice about an E motor) at stall, But horsepower is the rate you do work, That is how fast it spins and torque at that rate. You need numbers like those to I calced to get the HP you stated.

I do find this interesting too (much stuff about this too on web). I am impressed how much power the batteries can deliver. But so short lived. So I just can't get hooked into this unless I drag race. I street ride and I thought my gt550 had bad mileage range per charge/fill up

Fun stuff ( any type of energy transformation to mechanical )

I am impressed at your hobby and thanks for sharing it.

It seams like hill climbers know how to make long swing arms