Forklift motor for bike?

Hey all, i'm thinking of electrifying my KLR650, i haven't ridden it in years and i just can't bring myself to feed it with fossil fuels anymore, so i've decided to look into making it electric.

Now if i'm going to convert it, i'll need a big, high torque motor as it's a big, heavy bike, and i need a ton of torque to make it feel alive. The stock motor puts out something like 40ftlb of torque but i want more, and less top end as the bike is already too fast. Right now redline is like 110mph but i don't really need much more than 60mph or so out of it.

So, what's the deal with forklift motors for bikes? Is there a motor out there that can do this kind of thing? I want scary low end power on it, the kind of power where a bit too much throttle will flip the bike. Me and the bike are both big, heavy beasts and i'll need to be able to power up steep offroad stuff, like near vert hillclimbs, launching double sets, and such.

So is there a good choice for a beastly, oversized motor that can provide a wildly excessive amount of torque?

Ideally you need to find a motor that has a fairly decent rpm 3500 + or the rear sprocket needed will be larger than then wheel itself for a direct drive and a gearbox with all sorts of added losses will be needed I'd say try pick a motor that has a decent rpm range and lots of torque for the wheelie machine u want

A common DC forklift motor with the right gearing and voltage at the high end of its limits could give you what you want...for a few miles. The problem is the relatively low efficiency compared to modern brushless motors. The 80ish peak efficiency of common DC motors will cause it to build up heat and quickly lose power and reliability.

First, I'd suggest starting with something much lighter, because unless you'll settle for limited range, the battery pack will quickly turn it into a significantly heavier bike than it is now.

Second, find out if Zero is still selling its 54hp high efficiency drive system. If so, then that will get you what you want.

Third, don't waste time with lead acid batteries. That's how I started with electrics, a moto conversion using lead batteries, and it was a heavy, slow, pig of a 2 wheeler, and every single ebike I've built since outperformed it by a wide margin. That was 10 years ago, and since then lithium (which was already better by a wide margin) increased its energy and power density by at least double, and cost have decreased by half.

Seconding what these posters have already said. Don't waste your time trying to repurpose that kind of tech. I've worked with some electric heavy machinery (narrow-aisle reach trucks, motorised walk-on pallet jacks, actual forklifts), as well as their propane-powered counterparts, and you'd really only want to steal the wiring from them (or perhaps get parts out the heavy duty controllers and chargers). Those batteries are so heavy, they're engineered to act as the counterweights to the load you're picking up—thousands of pounds. You could make a huge battery bank from them, but you don't want to be trying to carry them around at high speed. That technology is not built for that. Rather, it's designed for picking up extremely heavy loads on forks, slowly and steadily. I mean you could try to get it to work, but nothing about it would be optimised. Instead, invest in the technology that is literally built for that purpose. Using an 8kW QS hub motor paired with a 500A-peak Kelly controller and a strong lithium setup got me popping wheelies unintentionally on my scoot. I have to lean way forward when I take off or I might go flying. But for a KLR, a hub motor might not be your best option unless you go the spoked route, given that KLRs have pretty big wheels. Zero's motors, which are in-runners, would get you there more easily. There are many leading brands. Things to focus on are the parts that get you tons of startup torque. That generally means high amperage capabilities, so a good set of batteries that can reliably output in the hundreds-of-amps range, coupled with a controller and motor that will safely draw such power, will get you where you want to be. Maybe you could pick some parts (perhaps starting with the motor) and provide your riding weight (minus the ICE motor), and some educated folks could guide you from there. May as well get your measurements for where the battery's going to go while you're at it.

The forklift motor on a bike (and other small vehicles) has been done before, but it's big and heavy and inefficient. Remember--for it's intended purpose, it's actually *better* for it to be heavier than it needs to be, as ballast weight.

Here's a search of EVAlbum.com for "forklift motorcycle" which lists a few
evalbum search


Sure, you can gear it low and give it big amps and get all the low-end you want, and give it voltage enough to get your desired top speed. (or run it thru your transmission).


But there's a couple of things besides inefficiency that brushed forklift (well, any brushed, but...) motors have as an issue, and one of them is max RPM before commutator explosion. Whatever the nameplate rating is for RPM can probably be exceeded, but it has that limit for a reason, so you want to stay under it if you can. Beyond that, only testing to destruction would tell you where the explosion point is.

The higher the voltage, and the higher the current, the worse the brush/comm erosion is, and the more heat you get from arcing at the brushes.


I don't recall who it was, but on DIY Electric Car there were at least a couple of comm explosions on car/forklift motor conversions from overspeed, though I don't remember what exactly happened to cause them. It's been several years.





Anyway, if you don't mind brand new stuff / have the money for it, QSmotor makes some good hubmotors (and probably has controllers to run them) for motorcycle use, though I don't know anything specific about them. There's a thread in the for sale for their stuff though.


An advantage of a hubmotor is you could do 2WD, which would add wieght to teh front end and traction help for climbs (though I don't know how that would really work out as I don't use my 2WD for that sort of thing, just for the huge accleration advantage I get out of it).

If you'd rather use the existing drivetrain, you can go with stuff like the Methods/etc Zero motor and Sevcon controller; there's a thread for that too, in the motor technology section.


Or there's a lot of other ways to do it too.



But either way, I'd completley skip the lead-acid, and go with some form of lithium battery, becuase for the same weight you can probably get at least four times the capacity and capability, not to mention lifespan, even if you use recycled Leaf or Tesla or whatever cells. (which are also all available in the for sale section).

Thanks for the input!

I'm wanting to use the KLR not just because i already have it, but because the size of it fits me comfortably, smaller bikes are just too small, i've ridden other 650's without the KLR stance, travel, and geometry and they're basically toys. I've already got 16" clearance of tuned progressive suspension and performance brake system and all the guards and bashplates to let it go down and not break anything.

I want to do it more for the fact that i want a KLR, not just an electric bike, but specifically this bike's geometry and performance. I've ridden a lot of bikes but nothing as fun, capable, or confidence inspiring or anywhere near close. I've wheelied over a javelina like a speed bump at 60mph on it, where on any other bike i'd probably be dead. My only beef with it is that i'd like more bottom end and a faster low range response than the thumper powerplant can provide.

I'll check out the options mentioned above after work today!

Rusty Mustard said:

Thanks for the input!

I'm wanting to use the KLR not just because i already have it, but because the size of it fits me comfortably, smaller bikes are just too small, i've ridden other 650's without the KLR stance, travel, and geometry and they're basically toys. I've already got 16" clearance of tuned progressive suspension and performance brake system and all the guards and bashplates to let it go down and not break anything.

I want to do it more for the fact that i want a KLR, not just an electric bike, but specifically this bike's geometry and performance. I've ridden a lot of bikes but nothing as fun, capable, or confidence inspiring or anywhere near close. I've wheelied over a javelina like a speed bump at 60mph on it, where on any other bike i'd probably be dead. My only beef with it is that i'd like more bottom end and a faster low range response than the thumper powerplant can provide.

I'll check out the options mentioned above after work today!

Click to expand...

You will get more bottom end beef alright with a good bldc motor you will proberly have to dial it back not to have a full on death trap.

I'm afraid my friend all that time spent dialing in the suspension will need to be altered an electric setup will increase and move the weight around substantially even if a short range blaster is made using lipo I suspect it will feel a complete different bike to ride and jump with different pitches etc but it will go like shit of a shovel and tow cars.

http://www.evalbum.com/3020

http://www.diyelectriccar.com/forums/showthread.php/suzuki-drz-sm-2005-electric-48239.html

This is a beautiful Suzuki DRZ build using a series wound DC motor. There was tons of custom work and the builder made a 90 deg gearbox from scratch to get the long motor to fit longitudinally in the frame. The headway batteries are pretty heavy by today's standards and but I think this build ended up a few lbs heavier than the bike was stock. The thread from diyelectriccar seems to have mostly dead picture links but the evalbum post should give you the general idea.

If I were trying to power a motorcycle on the cheap I would get the most powerful scooter hub I could find and put it in the frame chain driving the back wheel at a large reduction. I'm thinking along the lines of the hubmonsters that John in the CR used to sell running as high of voltage as possible. Fill the rest of the frame with RC Lipo and you could have a pretty affordable 20-30kw bike. That might come up a little short on your power needs if you are using the KLR to its full potential. QSmotor sells a dual stator water cooled 273 motor but I bet thats pushing 50lbs. Big hub motors are relatively cheap and don't require high tech expensive controllers to run them. They are easy to mount and don't require super precise gear reductions to get reasonable RPM at the rear wheel. They are a bit heavy though.

If you go duplicating a zero you are probably going to be in striking range of the zero's price by the time you get done. If you love the KLR that much it may be worth it to you to go that route but its hard to resist financing a zero and spending your time riding rather than building.

My brother has a KLX which is very similar to the KLR and I can definitely see the charm. Its one of the only dirtbikes that I have ever jumped on and felt totally at home on in the first 2 minutes of riding.

Thanks, i'm going to research these suggestions and do some calculations to see what i can do about weight.

The KL series are awesome bikes, a friend of mine had the KLX and we'd trade bikes some days. Both of them are the most locked in bikes i've ridden when drifting as well as having the stance and clearance to just suck up stuff that the smaller bikes get upset by, and that makes them fast without even trying.

And it's not as much attachment to the KLR, it's just that if i start with a smaller bike it's going to take a lot more work to get anywhere near that kind of height and travel, and by the time i beef up the frame where the pegs mount it'd probably weigh just as much. I've snapped the stock pegs off every dirt bike i've had, including the KLR twice, so now any bike i ride hard is going to get welded on cage pegs. Stock pegs are always too small and weak, and i've cracked a couple of frames at the pegs as a kid.

And changing the suspension setup isn't a big deal now, i've got the heaviest progressive springs they make which gives me headroom to adjust sag, as well as fine tuning with air pressure. I can also tune the damping and oil weight, when i took the extra weight off the front i had to use lighter weight oil, like 7.5w. On the rear i can just make whatever size 'dogbones' (pivot linkage where length determines ride height and leverage) and tune the preload.

Basically though, if i've got to go with a smaller bike than this, i'd rather just build my own beefed up fat MTB frame and put one of those big hub motors on that, maybe swap a YZ80-125 fork up front and set it up like a technical freeride hardtail with high bb, short chainstays steep headangle and a long low toptube.