need hypothetical numbers for project

[The Atomic Ass]

Originally Posted by dremd

I'm no expert; but I'd bet that 7" motor would have more torque than the Busa transmission can handle.

Depends on how much the motor is going to put out. The Hayabusa has it's primary ratio between the crank and clutch I believe, and it's something like 1.7:1. Then comes the transmission.

I know for a fact some people boost up to double the HP of the stock engine without even touching the transmission. So that is perhaps, 300+ ft lbs on the input shaft?

But then again, I see gears only as a necessary evil of gas engines.

Also: AC! Better than DC.

[Electric Frenzy]

yeah but AC = much more $$ than DC.

I think we're just going to mock it up in a simple chassis and see what it feels like on 72v. It feels impressive then we'll just build it. If it needs work then we'll sit down and crunch the numbers. It would be easier to build the adapter plate to mount everything up than it would to track down specs on every gear and do the math.

[dcb]

FYI, I was digging through some Tesla info, it has no gears either. But it does have lots of torque down low w/gear reduction and a wide rpm range.

1. Single speed
2. 0-60 in 4 seconds
3. claimed 160mpg equivelant
4. ~230 mile range (lithium ion)
5. top speed 125 mph (electronically limited)
6. 2723 lbs, fully charged

Battery: 6,831 standard 18650 Lithium-Ion cells (400volt system)

Motor: 3-phase, 4-pole AC motor - unique design
215 kW @ 7,000 rpm (288 bhp)
Max torque (350 Nm) at zero rpm, max speed 13,500 rpm
Weighs 50 kg

Transmission
Single speed double reduction bespoke transmission
Reverse? - reverse motor direction!

[dcb]

So if you could halve the weight and the CDA of the tesla, you could have similiar performance with half the motor and batteries, and no gears, I think

If you could live with 1/5th of the 230 mile range, you could maybe use 1/5 of the battery pack (if the remaining batteries can still deliver the performance).

edit 683 of those li-ion batteries would be like 70 lbs!, the tesla is carrying about 700lbs of them, there is an easy weight (and cost) cut there.

more specs on that battery:
Specifications: Nominal Voltage :Average 3.7 V Nominal Capacity :2350mAh, Minimum 2300mAh Max. Charging current: 2.4A Max. Max. Discharging current: 4.6 A max. Dimensions: Diameter 18.3 mm (Max 18.4), Height: 64.9 mm (Max 65.1) Weight : 46.5 g (1.64 oz) Internal Impedance: Internal Impedance: less or equal to 90 mohm (with PTC) Cycle Performance: 80% of initial capacity at 300 cycles

So that 7 strings at 400v would be 756 batteries. Which could deliver 32.2 amps @ 400volts or ~17HP. Scaled up that would "only" be 170 HP so I think that tesla either has better batteries, is over pushing them a bit, or has more motor than the batteries can fully utilize.

[Electric Frenzy]

ok bear with me here. I'm trying to follow everything you've said.

1. You're suggesting I mimick the Tesla Roadsters motor and battery pack but scale it down by 80%?

2. The CDA is what exactly? Coefficient of drag?

3. You're saying with 1/10th of the battery pack they're using I should be able to go 46miles per charge? for about 70lbs worth of weight (in the batteries)

4. "Transmission=Single speed double reduction bespoke transmission" I'm not familiar with these. I don't understand how gear reduction transmissions work as they relate to electric motors.

5. I'f I'm using a DC motor I'd still need a trans for reverse as I wouldn't be able to just reverse the polarity of power going to the motor. Is that correct ?


I'm loving this discussion. I'm learning more every day.

[Electric Frenzy]

Check this out and see if I'm following you correctly.

This is a link for an AC electric motor. It's 3phase and rated at 10hp and 3600rpms. That seems awfully low for a vehicle. Obviously I'm not looking at the right item but am I on the right track?

01036EP3E215T - WEG ELECTRIC CORP MOTOR 3PH 10HP 3600RPM 215 T 208-230/460V


Here is another motor rated at 20hp @ 1800rpms. It costs $1000 but that is VERY cheap compared to others I've seen. It seems with this type of low rpm motor I'd NEED a transmission to compensate for that. Sure I wouldn't need 6 gears but maybe 3.

http://www.galco.com/scripts/cgiip.e...pnum=U652-MARA

[dcb]

Originally Posted by Electric Frenzy

1. You're suggesting I mimick the Tesla Roadsters motor and battery pack but scale it down by 80%?

50%, lets say you keep the battery pack at 400 volts, but use half as many cells as the tesla (and half the motor).

And you can do that because you figured out how to reduce the coefficient of drag(CD) multiplied by the frontal area (a) in half (or CDa) so top speed will be similiar

And you also figured out how to halve the weight of the vehicle so you have half the mass of the tesla, and half the power, so acceleration should be similar, though rider weight will have a larger influence.

Originally Posted by Electric Frenzy

3. You're saying with 1/10th of the battery pack they're using I should be able to go 46miles per charge? for about 70lbs worth of weight (in the batteries)

The tesla batteries are at their max for these acceleration figures, the 1/10 pack numbers didn't work out, sorry. 1/2 the number of batteries works, and is a healthy bit of weight to lose still. You'll just have to live with a 220 mile range

Originally Posted by Electric Frenzy

4. "Transmission=Single speed double reduction bespoke transmission"

A couple gears, you can't shift them but they make more torque at the rear wheel. According to the specs it is 8.28:1 overall ratio. It would be like having a 10 tooth front sprocket on the motor connected to an 83 tooth rear sprocket, not that those are practical sprockets, but sprockets are fairly simple to make too (lots of drilling)

Originally Posted by Electric Frenzy

5. I'f I'm using a DC motor I'd still need a trans for reverse as I wouldn't be able to just reverse the polarity of power going to the motor. Is that correct ?

We are in the motorcycle section. Who cares about reverse? How will you reduce frontal area substantially if you have more than 2 wheels? OR the weight? We are talking about a bike right? But DC motors are reversable, just got a bit more controller expense though. Might use 2 motors (each at 1/4 the tesla motor outout) and use the killicycle series/parallel shift for possibly more performance, but still direct drive.

[dcb]

Another approach might be to thumb through the EV album for motorcycles till you see some specs that you like and see what equipment they have listed.

EVAlbum: Search Results

Like this guy with 50 mile range and top speed of 100, and acceleration of "very fast". It looks like you can go buy one of these today for ~$16k from their website. Go hitch up the trailer Looks like it is in Charlotte (400 miles from you)

[Electric Frenzy]

reverse is mandatory. What I'm wanting built is a fully enclosed 3 wheeler which is LEGALLY a motorcycle. I like the one pictured above but I have a 250cc if I need some 2 wheeled fun.

I've been doing some searching and I'm finding numerous 3ph AC motors with 20hp and rpms ranging from 1800-3600. I don't know if these will work but if so they are priced reasonably and would allow some extra money to go towards battery packs.

Speaking of Batteries..... where would I go to research and price custom built LiIon battery packs like you mentioned needing above?

[Electric Frenzy]

p.s. I've checked out that link you posted to the electric motorcycle company. There is a lot of debate on other forums about how legitimate they are. They make a lot of claims that seem HIGHLY dubious. (30minute charging of LiIon and 80mile range with stellar performance) No'one else can do that and certainly not for that price.