2 brushed motors 1 controller with "Turbo" button

[John in CR]

I'm planning to try a 2wd rig using dual Dewalt hammerdrill motors and gear boxes using a Kelly 100/200 controller, since these things can pull serious amps. I'd like to use just one controller, but not use both motors at all times. Instead, I'd like to use a button to control a contactor between one motor and the controller, so that motor only kicks on to accelerate fast or to help climb hills. Maybe I'd use a pair of contactors and switches instead of a button to be able to use either or both motors, so I can alternate between them and be less demanding on them through intermittent use as opposed to continuous use on one.

I think what I want to accomplish makes sense, but my question is how will my brushed controller act with this abuse? Would there be a problem switching from the controller seeing one motor to two, or from two back to one? Is it something I can do under load, or would I have to let off the throttle first when going from 1 to 2 or back to 1? Any ideas for a better way to do it?

John

 

[billvon]

I'm planning to try a 2wd rig using dual Dewalt hammerdrill motors and gear boxes using a Kelly 100/200 controller, since these things can pull serious amps. I'd like to use just one controller, but not use both motors at all times.

Why would you want to do this? You don't get any power or efficiency advantage; you're incurring the mechanical drag of both motors anyway. I suspect you'd be slightly more efficient running both motors at once full time since you'd reduce I2R losses in the controller to motor wiring and windings.

 

[ZapPat]

Dropping your throttle to zero, then connecting the additional motor in parallel using a contactor, high power relay, or even a manual switch should work OK.

However, as billvon points out, you might be better off leaving both connected all the time. If in doubt, try both setups (one and two motors) on the same run and compare results... and let us know how it went!

 

[John in CR]

I'm planning to try a 2wd rig using dual Dewalt hammerdrill motors and gear boxes using a Kelly 100/200 controller, since these things can pull serious amps. I'd like to use just one controller, but not use both motors at all times.

Why would you want to do this? You don't get any power or efficiency advantage; you're incurring the mechanical drag of both motors anyway. I suspect you'd be slightly more efficient running both motors at once full time since you'd reduce I2R losses in the controller to motor wiring and windings.

Why?...to have 4.4hp available for acceleration and hill climbing, but use only one on the flats. Also intermittent use instead of continuous use is exactly what the units are designed for. Each would have it's own freewheel, so the mechanical drag when not in use would be almost 0. I just don't want to blow a controller, and I don't want to buy a second controller unless it's necessary. I could use the throttle and control electronics from the tools themselves, but I already have the Kelly and I think it would be better and more efficient anyway. Running both motors all the time would reduce gearbox and brush life, and increase noise. Wouldn't the losses of the 2nd gearbox be greater than the I2R benefit anyway?

John

 

[RLT]

John has a point... only because of the freewheel and the gear boxes, though.

I used similar, (but faulty) logic in the original design of my 2WD, but quickly changed it to both being full time powered. On non-freewheeling hub motors, that seems to be the way to go.

But with the setup he is talking about, part-time 2WD makes sense.

That said.... If I had it to do over, I wouldn't have done 2WD at all;
Knowing what I know now, I'd have just gone with the most powerful rear motor I could get.

Oh, to answer the original question.....
I'm using the same Kelly controller (mine is 48V), and I think it will handle the setup OK, although I'd be careful to cut in/out the motors when coasting, or at least with very light throttle; NOT under acceleration or heavy hill climbing power

 

[John in CR]

...That said.... If I had it to do over, I wouldn't have done 2WD at all;
Knowing what I know now, I'd have just gone with the most powerful rear motor I could get.

Oh, to answer the original question.....
I'm using the same Kelly controller (mine is 48V), and I think it will handle the setup OK, although I'd be careful to cut in/out the motors when coasting, or at least with very light throttle; NOT under acceleration or heavy hill climbing power

RLT,

Please give us the details. I haven't been able to find much about 2wd 2 wheelers, other that an old gasser that people loved other than the mechanical troubles of the front drive. On a typical lightweight bike, I'm very concerned about lifting the front wheel with all that torque, and no way I want the power of 2 on the front, though I'm comfortable with my current overvolted front drive hub. Are there handling issues with 2wd, (It sounds like fun in mud and sand), or where your issues with having dual drivetrains? For off-roading in the mountains 2wd seems much better than rear only.

I've ridden enough motorcycles that getting off the throttle to go to dual will be easy. I'll have to do it to change gears on the gearbox anyway. Thanks for letting me know that getting off the throttle is important.

John

 

[billvon]

Each would have it's own freewheel, so the mechanical drag when not in use would be almost 0.

Ah, I see. I agree; with a dual freewheel, you'd get reduced drag when running from only one motor.

I just don't want to blow a controller, and I don't want to buy a second controller unless it's necessary.

Using both on one controller should work fine provided both wheels are the same diameter and the gearing is the same for both motors. If not, one motor will shoulder most of the load even when both are connected. It will probably be able to change on the fly, but going to zero throttle before switching would be safer.

Running both motors all the time would reduce gearbox and brush life, and increase noise.

Noise - agreed. Gearbox would depend on torque seen. Not sure about brush life. Would halving the run time of the motor make up for doubling the current in the active motor's brushes?

 

[John in CR]

... Gearbox would depend on torque seen. Not sure about brush life. Would halving the run time of the motor make up for doubling the current in the active motor's brushes?

Good point about the brushes and current (other than the no-load current with gearbox at that speed). Brushes are just $5, and later the replacement gearboxes may be difficult to find. With 10-30krpms, I'd think the gearbox wear factor may not be too weighted toward torque, especially since we're talking about cruising on the flats anyway. To me more noise means more gear wear, or am I looking at it wrong?

John

 

[RLT]

RLT,
Please give us the details. I haven't been able to find much about 2wd 2 wheelers, other that an old gasser that people loved other than the mechanical troubles of the front drive. On a typical lightweight bike, I'm very concerned about lifting the front wheel with all that torque, and no way I want the power of 2 on the front, though I'm comfortable with my current overvolted front drive hub. Are there handling issues with 2wd, (It sounds like fun in mud and sand), or where your issues with having dual drivetrains? For off-roading in the mountains 2wd seems much better than rear only......

Yeah, I was going to buy a Rokon 2WD motorcycle about 5 years ago, then at the last minute, the guy (an authorized Rokon dealer) pulled out of the deal we had made, and I was so mad at him I just went and bought an ATV instead. But the Rokon was definitely the inspiration for my build.

Well, weight is definitely one of the two main issues. Between my batteries and the hubmotor, there is 42 or so extra pounds in front of the handlebars; and while it handles better than one might think, it takes a lot more effort to maneuver. I don't have any room in the middle to mount enough batteries to run a flashlight, much less, a motor, so it might be a different story if I could get the range and power I need with a single, middle mounted battery pack.

Not only weight distribution, but total weight. I'm a pretty big guy, but when the bike leans over past its tipping point, it takes a lot of effort to hold it up.

And just the complexity of the build.... wires going everywhere, nearly twice as many things to hook up, nearly twice as many things to go wrong.

As to off-road, which was my main purpose for this bike; sand mud, gravel... I'm not certain that traction is all that much better with both wheels under power or not. Not having ridden a single wheel (rear) drive Ebike, I can't give an honest comparison, but I think that I'd rather have the ability to pop up the front wheel and be more nimble.

Don't get me wrong; I do like my bike and enjoy riding it, and the 2WD gives me some kind of 'bragging rights' , especially with the folks that are into Jeeps and such. But I have a nagging feeling that if I had gone with a single 53xx in the rear, I'd be happier..... And have saved a few hundred hours of tinkering and building time. And money.... Would have cost more for the single motor and controller than I paid for both Wilderness Energy kits, but by the time I got the system 'perfected' I spent twice as much.

When I first started my build, I couldn't find any info about people who had actually built a 2WD bike, mostly just people that thought it would be either really cool or really stupid. Since then, I have seen mentions of 4-5 other people that have done it, but no real documentation of the builds or performance. And a couple of the 'pioneers' in the idea have gone back to single wheel drive.

I'd pull the front hubmotor off of mine and give it a try to see whether the difference in handling makes up for the (possibly) greater traction off road, but I'd burn up a single WE motor or have to pedal a lot more than I want to to get up the hills around here. So that's why I say go with a 53xx series. --- (or a geared hub motor).

 

[John in CR]

RLT,
Please give us the details. I haven't been able to find much about 2wd 2 wheelers, other that an old gasser that people loved other than the mechanical troubles of the front drive. On a typical lightweight bike, I'm very concerned about lifting the front wheel with all that torque, and no way I want the power of 2 on the front, though I'm comfortable with my current overvolted front drive hub. Are there handling issues with 2wd, (It sounds like fun in mud and sand), or where your issues with having dual drivetrains? For off-roading in the mountains 2wd seems much better than rear only......

Yeah, I was going to buy a Rokon 2WD motorcycle about 5 years ago, then at the last minute, the guy (an authorized Rokon dealer) pulled out of the deal we had made, and I was so mad at him I just went and bought an ATV instead. But the Rokon was definitely the inspiration for my build.

Well, weight is definitely one of the two main issues. Between my batteries and the hubmotor, there is 42 or so extra pounds in front of the handlebars; and while it handles better than one might think, it takes a lot more effort to maneuver. I don't have any room in the middle to mount enough batteries to run a flashlight, much less, a motor, so it might be a different story if I could get the range and power I need with a single, middle mounted battery pack.

Not only weight distribution, but total weight. I'm a pretty big guy, but when the bike leans over past its tipping point, it takes a lot of effort to hold it up.

And just the complexity of the build.... wires going everywhere, nearly twice as many things to hook up, nearly twice as many things to go wrong.

As to off-road, which was my main purpose for this bike; sand mud, gravel... I'm not certain that traction is all that much better with both wheels under power or not. Not having ridden a single wheel (rear) drive Ebike, I can't give an honest comparison, but I think that I'd rather have the ability to pop up the front wheel and be more nimble.

Don't get me wrong; I do like my bike and enjoy riding it, and the 2WD gives me some kind of 'bragging rights' , especially with the folks that are into Jeeps and such. But I have a nagging feeling that if I had gone with a single 53xx in the rear, I'd be happier..... And have saved a few hundred hours of tinkering and building time. And money.... Would have cost more for the single motor and controller than I paid for both Wilderness Energy kits, but by the time I got the system 'perfected' I spent twice as much.

When I first started my build, I couldn't find any info about people who had actually built a 2WD bike, mostly just people that thought it would be either really cool or really stupid. Since then, I have seen mentions of 4-5 other people that have done it, but no real documentation of the builds or performance. And a couple of the 'pioneers' in the idea have gone back to single wheel drive.

I'd pull the front hubmotor off of mine and give it a try to see whether the difference in handling makes up for the (possibly) greater traction off road, but I'd burn up a single WE motor or have to pedal a lot more than I want to to get up the hills around here. So that's why I say go with a 53xx series. --- (or a geared hub motor).

Thanks RLT,

I'm sorry that I didn't recognize you, because I've read about your build in the photos & video section, and it's a big part of why I insist on attempting 2wd. Wow, I did not realize you were at 42lb in front of the handlebars. I'm trying to get away from the 12lb or so hub motor I have there now. These motors and 2 or 3 speed gearboxes plus mounting hardware, chain and sprockets will come in under 4lbs front and 4lbs rear, so virtually nothing. I'll customize the frame to fit up to 1.5-2kwh of batts in the triangle, but for most fun riding a 10 or 15lb pack should be sufficient. With 69 ftlbs of torque fed to each wheel in low gear and 4.4 times the rpms in high gear, it should be a fun 50-60lb featherweight that can climb places a motorcycle can't and still hit 40mph on the flats. With the simplicity of brushed motors, I look at the 2nd motor as backup in case I break a chain or sprocket, not additional points of failure, and with the total cost of motors and gearboxes less than $200 it would be almost stupid of me not to try, especially since I have the controller and sprockets collecting dust.

John

 

[RLT]

Good luck with it. It will be a great learning experience and a great conversation piece., and maybe you will start a trend

 

[wasp]

i like the ideal
and think if you pound on 1 motor you can switch to the other
allowing the first to cool ...

 

[eP]

With the simplicity of brushed motors, I look at the 2nd motor as backup in case I break a chain or sprocket, not additional points of failure, and with the total cost of motors and gearboxes less than $200 it would be almost stupid of me not to try, especially since I have the controller and sprockets collecting dust.

Cheap, 80% max. efficient motor is fair enough as the backup IMO.
But primary motor should be 86-88% efficient at 1.5 - 2kW power out power level unless you don't want dissipate too much heat.

For 80% efficient primary motor you would need a lot of dense gears to keep efficiency at decent level.

BTW: how much you are going to spend on batteries subsystem ?
How long you are going to use them until they must be replaced ?
Maybe you should spend $100 or $200 more for motors and drivetrain to gain 5 or 10% extra efficiency (for the sake of total costs).

Best regards

 

[John in CR]

eP,

These drillhammer motor are self ventilating, so heat buildup isn't an issue. If you know of 1-2 pound motors near this capacity with mid to high 80's efficiency, please direct me. I'll leave the RC motor solutions to others right now, though they may want to give these 1lb transmissions a try. Bell housing distortion, low speed controller issues, and heat buildup have me putting exploring RC's on hold. For me it's an experiment more than anything to see if I can get high performance for cheap, and to see how these gearboxes hold up. If it works, someone on a tight budget could just buy the drill, some cheap lead batts, sprockets, chain, and use the built in throttle and control. For under $200 and some elbow grease, they end up with an e-bike conversion that will out climb and outrun any of the kits that are double the price. With lots of stop and go or hills, the multi-speed transmission may even prove to be more efficient in real world use, which is another reason this should be tested.

John

 

[eP]

These drillhammer motor are self ventilating, so heat buildup isn't an issue. If you know of 1-2 pound motors near this capacity with mid to high 80's efficiency, please direct me. I'll leave the RC motor solutions to others right now, though they may want to give these 1lb transmissions a try. Bell housing distortion, low speed controller issues, and heat buildup have me putting exploring RC's on hold. For me it's an experiment more than anything to see if I can get high performance for cheap, and to see how these gearboxes hold up.

What do you mean by high performance ?
High power in and high heat dissipation ?
If you start with high 70's motor efficiency then you end with mid 60's efficiency of whole system i'm afraid.
It doesn't mean high performance for me.

If it works, someone on a tight budget could just buy the drill, some cheap lead batts, sprockets, chain, and use the built in throttle and control. For under $200 and some elbow grease, they end up with an e-bike conversion that will out climb and outrun any of the kits that are double the price. With lots of stop and go or hills, the multi-speed transmission may even prove to be more efficient in real world use, which is another reason this should be tested.

So are you going to use lead acid batts for your setup, really?
Than tell us how much weight you want to install ?
And what is your wh/m goal ? 30, 40 or 50 wh/m ?

What do you mean by "outrun any of the kits that are double ithe price " ?
Range ?
Speed ?
Acceleration ?

 

[John in CR]

eP,

I don't care about the mpg of a sportscar, and that attitude carries over to e-bikes. Due to my short trips I only charge my lifepo's a couple of times a week, so efficiency is unimportant. Right now I'm running a front hub at 85V to which I'm adding a rear geared hub to improve acceleration and hill climbing. For me wh/mile is mostly an interesting number, and I consider performance to be speed and acceleration. I'll wait for battery advancement and cost reduction before tackling the 80mile ride to the beach. I have some lead I don't want to go to waste, so I'll put that on a short trip grocery and kid hauler I'm building. It is already going to be heavy due to the 25lb 4.5hp powerpack motor and right angle worm gear drive powering it, so 40-50lbs of lead won't really matter.

This Dewalt hammerdrill bike will be a totally different animal. I want 2wd, hill climbing and acceleration on a flyweight bike. I'll probably get some RC litium packs for running around the park and river next door. For a lengthy ride in the mountains, I'll need to load up a bunch of my NiMH's. If I can get satisfied with performance with me at 240lbs, then those solutions should be good for for everyone but the long range crowd. To me it's really up to the chemists and materials engineers to satisfy their needs. I'm better at cheap and easy.

John

 

[eP]

I want 2wd, hill climbing and acceleration on a flyweight bike. I'll probably get some RC litium packs for running around the park and river next door. For a lengthy ride in the mountains, I'll need to load up a bunch of my NiMH's.

So once again i have to ask the previous question: how much really you want to spen on batteries ?

Is that really good choice to go to mid 60's % inefficient second drive system to save $100 ?

 

[John in CR]

I want 2wd, hill climbing and acceleration on a flyweight bike. I'll probably get some RC litium packs for running around the park and river next door. For a lengthy ride in the mountains, I'll need to load up a bunch of my NiMH's.

So once again i have to ask the previous question: how much really you want to spen on batteries ?

Is that really good choice to go to mid 60's % inefficient second drive system to save $100 ?

With my jackrabbit starts and stop and go riding with rarely a full minute of stable speed, do you really believe any single speed motor is going to do much better than 60% efficiency? Once I get a CA installed and get real numbers over the next couple of months, then we'll have some answers. I need some higher C batteries anyway, so what I spend on batts is irrelevant to whatever bike I put them. Over the next 6 months, I'll be trying a number of different alignments. The powertools parts bike is just one, but I'm sure a lot more R&D went into their development than into motors for e-bikes. Efficiency and power are of critical importance in the applications for which they are designed. The 81% efficiency and 2.2hp was measured for the older 24v model, so it's quite likely that the newer 36v motors and gearboxes are better. Also, the info was unclear whether the 81% is before or after the transmission.

Like I said, this is just an experiment, so I don't understand your resistance to me giving it a go. I also have some big hub motors used on small motorcycles that I also plan to test, which are in route from several factories. They only claim mid 80's peak efficiency. Are you going to knock giving those a try as well? As I asked before, if you have some ideas for better motors to try that I can pick up for reasonable prices, please direct me to them.

John

 

[lawsonuw]

I've played a bit with the Dewalt motors and gearboxes. They're good motors. The pinion's are M0.7 on the smaller motors and the old hammer drill motor. Looks like the new 36v motor might be a M0.8 pinion. (lots easier to find M0.8 gears!) The gearboxes are also well built, with hardened powder metal gears. A few details can make them a pain to deal with though. Basically the Dewalt motors and gearboxes are designed to live in a fancy molded case so making a replacement mounting is artsy. Also, the output shaft is totally unsupported so several bearings will be needed externally to support it. If the case of the drill can be purchased for a reasonable price, it will save a LOT of trouble. (btw, Dewalt allows most anyone to purchase any part to their products on the Dewalt service website if you register) Getting an output shaft and bearings wouldn't hurt either.

The "silver cross thingy" on the output of the transmission is a clutch to prevent back driving of the transmission. It's useful in a drill, but could cause real mayhem on a bike. I'd remove it.

My 2Wh,
Marty

P.S. As with any brushed motor, breaking in the brushes will make the motor more efficient and last longer. (run the motor at low speed/voltage for 5-10 min)

P.P.S. WHOOT mounting holes on the front plate! Still, the front plate of the motor is likely only staked on. Would need a few tack welds before it's ready for combat service.

 

[John in CR]

Marty,

Thanks for the input and for the reminding me to break the brushes in. I can't tell how the speed shift works from the pictures. Is it a mechanism for which some kind of easy DIY linkage could permit shifting while riding? Regarding mounting, it's going to be mighty tempting to just relocate the tool throttle to the handle bars, throw a drive gear in the chucks, secure the entire drill to the frame, and give it a whirl with one motor to get an idea of how well it will work. It would be just a temporary rig, but given my impatience it could be almost as quick and easy as a front hub since I already have front and rear wheels ready with large enough sprockets.

John

 

[lawsonuw]

Regarding gears: The white thing surrounding the transmission is a cam that sequences the gears. The transmission will actually have 4 gears, but the cam only shifts through three of them. The shifting method involves sliding the ring gear of a stage towards or away from the motor. When slid towards the motor the ring gear is locked to the case. When slid away from the motor the teeth on the ring gear engage with matching teeth on the planet carrier locking that gear stage up. As these are dog clutches, shifting with everything spinning is a BAD idea. Still, a microprocessor and the right sensors could safely sequence a shift if that's required. Alternatively with two motors and freewheels, the motor's could be shifted one after another if they could be independently stopped.

Oh yea, keep the torque limiting clutch if you can. (it's on the outside of the first stage's ring gear, a spring loaded finger pushing on the ramps) "Click, Click, Click, Click, Click" is a much nicer sound to hear than "CRUNCH whiirrRR"

Marty

 

[docnjoj]

Oh boy! That "crunch whrrrrrrr" in geared motors is the sound of $ going down the drain!
otherDoc