[Jonbickford]

Hi everyone, tons of great information on this page.

I'm wanting to build a single seat mini buggy along the lines of a Honda Odyssey but electric. I will likely modify some kit plans for a buggy design that normally weighs in at around 618 lbs using a 650cc quad motor that weighs in around 120lbs and makes about 32hp.

I am thinking of using either an AC20 or AC23 from hpevs and running 22 or 24 CALB72 packs in series to power in the neighborhood of 72v/550 amps which should put my power curve right about where I want it.(wheelspin!) With a 60 pound motor and 88lbs of batteries it would make it pretty close in weight to the ICE motor and a gas tank, so it should be quick!

can the CALB batteries handle the top end current? they're rated for 580 max for 10 seconds, can they cruise around 550 for awhile longer?

can these cells handle a ton of vibration? I'd like to be able to flog the heck out of it around a little motocross style track safely.

am I realistic in thinking that I can get about 25 minutes of ridiculous fun run time out of a charge?

with a relatively short run time and a light-ish load to move around is liquid cooling necessary or am I ok staying with air cooled motor and controller?

Am I better off with the AC 23 with a ton of torque and use a higher gear for top end or with the ac 20 and being able to wind out into higher rpm?

Thanks so much!
-Jon

 

[galderdi]

Hey,

Your plan sounds sort of similar to my two projects. Although mine are designed mostly for bitumen. You can see them here:

http://www.diyelectriccar.com/forums/showthread.php/aussie-ev-autocross-special-ii-185897.html


http://www.diyelectriccar.com/forums/showthread.php?t=166009

My first one weighed around 1155lbs and was a front wheel drive two seater. My new one weighs around 1008lbs and is a mid engined single seater. Unless you are continually stopping and starting I don't think your batteries will need to sit at more than 500 amps for long.

For 25 minutes of hard driving you'll need at least 7kwh of capacity (that is what I have). But I recommend aiming a little higher.

I run a full gearbox, which adds to the weight but means gearing is no issue. If you choose to run without a gearbox I suggest aiming for the equvalent of 3rd gear. In my car 2nd gear gets me just around 60mph but 3rd would be more comfortable.

Wheelspin on dirt was a real issue for my first car as it was front wheel drive. You can see the videos if you search for "Full Charge Motorsport".

I can't help much with those CALB batteries. But let me know if you have any questions about the rest of my builds.

 

[Jonbickford]

I read through your newer car thread a couple of days ago that thing is awesome!

something similar to that for sure but a bit smaller and lighter and less powerful. I'm aiming for about 75mph top speed it doesn't really need to go faster than that for now. Being from Australia you might be familiar with Edge buggies, I want to do something kind of similar to their lightest weight suspended model.

The battery pack is at about 5.1 kWh as I'm currently picturing it and the idea would be to have 2 packs with 48lbs of battery in side pods on each side of the driver and have a second pair of packs to swap out. Trying to stay on budget and in the performance envelope I'm aiming for is tough and means some over simplified suspension and various compromises like that for cost, and weight.

I hadn't seen your first buggy yet that thing is really cool too! I love the video where they have you doing slalom between two concrete walls! too many lawsuits in America to do stuff like that anymore! very cool.

 

[galderdi]

Thanks, Yeah I am quite happy with how both turned out.


Sounds like you have a good idea of your target and a good plan.

If you skipped the gearbox you would probably bring the weight down to around 970lbs.
If you went with a lower power motor you might bring it down to 950lbs.
My roll cage and other safety features are designed to meet my sport's standards so you might save some more weight there.
My wheels, brakes etc are all designed to take the force of running on bitumen so you can probably run with lighter wheels, tyres and brakes to save more weight.
My batteries are around 135lbs so you can probably save some weight there too.

I am also sure someone with more experience could build the rest of the chassis lighter than mine. But mine is built to take some significant forces and I am guessing yours would need to be similar. However if you build a good roll cage you can use to add strength to a light weight floor.

 

[Jonbickford]

I am planning on doing just a chain drive, I may even do just a solid live rear axle on an ATV style swing arm to save a lot of weight. Not ideal for handling but in the spirit of "simplify and add lightness" I've also considered having the motor spin a jack shaft then running 2 sprockets on the shaft and 2 chain driven trailing arms in back.

Anything to keep the weight down and the strength up at this point at the expense of tidy handling, at least the center of gravity will be very low! Sideways isn't fast but it is fun and looks good on youtube! haha.

 

[brian_]

Being from Australia you might be familiar with Edge buggies, I want to do something kind of similar to their lightest weight suspended model.

The battery pack is at about 5.1 kWh as I'm currently picturing it and the idea would be to have 2 packs with 48lbs of battery in side pods on each side of the driver and have a second pair of packs to swap out.

So, the Sidewinder Plus, I assume. This would be an interesting configuration. It would be nice to have better suspension, though... the upgraded front suspension and something independent (or at least articulated) at the rear.

 

[brian_]

I am planning on doing just a chain drive, I may even do just a solid live rear axle on an ATV style swing arm to save a lot of weight. Not ideal for handling but in the spirit of "simplify and add lightness" I've also considered having the motor spin a jack shaft then running 2 sprockets on the shaft and 2 chain driven trailing arms in back.

That's was the Sidewinder has, but the idea of a suspension which forces the whole vehicle to roll with ground irregularities wouldn't work for me. It's not so bad on an ATV such as a quad that you straddle like a motorcycle, because it can toss around without your body moving to match, but strapped in a seat is different.

Still, lots of inexpensive sit-in ATVs have used this design.

I've also considered having the motor spin a jack shaft then running 2 sprockets on the shaft and 2 chain driven trailing arms in back.

Well, individual chains per wheel worked for antique trucks...
It actually does make mechanical sense to me in this case.

 

[Jonbickford]

yes exactly! the sidewinder plus was the initial inspiration, but It would be even cooler to stuff the motor behind the driver's lower back since it's only 7" diameter and 14" long, then close in those nerf bars to where they are basically side pods to carry batteries on each side.

I've only seen a couple of photos out in internet land with dual chain drives, It seems like a really simple and light solution and no worrying about cv joints handling electric torque... it might even be possible to make it weigh as little as the single swing arm since it doesn't have to take all the huge torsional forces though I suppose the jackshaft and extra chain and shock would take that advantage back.

 

[Jonbickford]

for expediency sake I may just do the sidewinder plans with the motor on the side and try to break up the battery packs to counter balance it out. then once I'm really happy with the power work on another design from scratch but I also wonder, how much more effort is it to just do my original design the first time?

I would like to have it rolling by the end of summer.

 

[Jonbickford]

there is also the option of doing something like the majority of cheap Chinese buggies do where they have the engine mounted to the swing arm, run two shocks and have some side to side absorption where the swing arm is sorta floating free a little bit. that's also popular for on road rc cars.

the AC23 weighs 60 lbs but since it's so small in diameter I think it could be mounted right at the very top of the swingarm above the pivot so it doesn't move very far with the suspension and lessens the beating the motor takes and the adverse effect of unsprung weight as much as it possibly could.

 

[brian_]

rear suspension

there is also the option of doing something like the majority of cheap Chinese buggies do where they have the engine mounted to the swing arm, run two shocks and have some side to side absorption where the swing arm is sorta floating free a little bit. that's also popular for on road rc cars.

This generally sounds like some sort of live beam axle on a locating frame which also carries the motor. Once you allow articulation (roll motion, or different travel on left and right sides), the simplest construction uses a big ball joint at the front, an A-frame to the axle, a couple of springs and shocks... and something to locate it side-to-side, such as a Panhard bar, Watt's link, or various more strange contraptions. It's that last bit which causes all of problems and complicate the structure, and by the time it's done well, I think it might as well be independent... even if that means the simplest trailing arms.

the AC23 weighs 60 lbs but since it's so small in diameter I think it could be mounted right at the very top of the swingarm above the pivot so it doesn't move very far with the suspension and lessens the beating the motor takes and the adverse effect of unsprung weight as much as it possibly could.

• If you do a single non-articulating (no roll) arm you can make the arm pivot on the same axis as the motor, or the same as the jackshaft (if using a two-stage chain drive); a differential would go on the axle line.
• If you do two independent trailing arms, you can go without a diff or with a diff on the jackshaft (if using a two-stage chain drive or first chain stage plus half-shafts). If it is a two-stage chain drive you can again pivot the arms on the axis of the jackshaft.

Either eliminates any motor motion or chain length change with suspension motion at all.

 

[brian_]

Side-mount motor?

for expediency sake I may just do the sidewinder plans with the motor on the side and try to break up the battery packs to counter balance it out.

I was thinking of the motor behind the seat, but I suppose with a heavy motor it could sit on one side with the controller and every other bit of hardware needed, and the entire battery on the other side.

With the motor on the side, a first stage chain drive could go back to a jackshaft behind the seat, and whatever is chosen for suspension and final drive from there.

Whether there is no battery or only a small battery section on the motor side, it seems like a limitation on battery size, and awkward for packaging easily handled battery packs. Meanwhile, there's not much useful happening behind the seat.

 

[brian_]

front suspension

Would it possible, and expedient, to salvage an entire front suspension with hubs from an ATV? People must wreck these things frequently, but I suppose the front end bits might not survive very often; perhaps a used machine with a dead engine might be a more likely source.

 

[Jonbickford]

completely agree on all points Brian! putting the motor right behind my butt with the shaft inline with suspension pivot is pretty much the most likely scenario I'm thinking, same concept as the sidewinder but with the motor in the middle of the swing arm pivots instead of to the side. I figure that would also protect the motor and chain a bit more and give me a lot of room to do what I want with the side batteries just like you said. it's also just a lot more elegant engineering and with such a small motor you don't really have to stretch the wheel base much at all from the sidewinder plans! on paper at least my design is actually a little smaller than the sidewinder in every dimension.

The dual chain trailing arms would be great, I could mount the jackshaft right behind the seat and the motor could be hung back behind that.

of course, if I went with dual chains I could have the option of running dual motors! but I haven't really found anything small that can match the power to weight ratio of an hpevs AC20/23 motor.

I've absolutely been looking at atv suspension on eBay and craigslist! a lot of people hop up their RZR and sell the original shocks and suspension arms off for pretty cheap, there's also a big aftermarket of heavy duty widened atv suspension kits available. if I figure out what model I want to use as a basis I should be able to get a pretty nice front suspension that way if not also the rear.

 

[Jonbickford]

how do I post pics on here? you guys seem to get exactly what I'm talking about but visual aids are always great.

 

[Jonbickford]

this is the coolest looking 2 chain setup I've found on the web so far I wish I could find more info about the car, but honestly, that looks great!

 

[Jonbickford]

these little cars are apparently a 600cc spec series in Finland, they have a side mounted engine and are pretty close to what I'm picturing. I've watched a lot of videos of them racing and the handling does leave something to be desired! at least in this case the batteries and motor will all be 8" off the floor and the only mass higher than that is roll cage and the driver's upper body.

 

[Jonbickford]

I want to stick to the size of a Honda Pilot basically. that is a buggy you can carry in the back of a pickup truck. The driver could sit further back so that his feet are behind the front axle line for safety because it doesn't need the space for the large bike engine behind the driver, and with the batteries on the sides the mass will be concentrated nicely between the axles, with longer side pods I can slide the batteries forward and back to play with weight balance. or just play with bigger batteries...

 

[Jonbickford]

in the case of the sidewinder, it's not ideal but it is the closest thing in terms of size, weight, strength and cost to what I had in mind for the original design goals that I have found! I could definitely make a fun buggy off of one and focus on the electric end not having to also worry whether my first ever blank page chassis design is sound.

 

[Jonbickford]

back of Edge Sidewinder Plus.