Using RC motors on E-bikes [Archive]
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dirty_d
10 kW
Matt, i forgot to ask you another question, how was your larger pulley secured to the shaft originally before the slipper clutch, did you mill a keyway into it, or something that a pin could go into and through the shaft like you have on the slipper clutch halves. oh yea, and how the hell is a keyway machined into a bore? it seems like the only possible way is if you have like a 90 degree gearbox small enough to fit into the bore that has a bit on the end to cut it
recumpence
1 GW
dirty_d said:
Originally it was pinned to the shaft.
A keyway can be done a couple ways;
#1 Inside a bore requires a tool similar to a chisel that drive into the bore leaving the keyway slot.
#2 You can even use a round key. I actually started doing that before I settled on a pin. The round keyway would be simply a hole drilled into the seam of the pulley and shaft then the pin is inserted into that hole.
Actually, a flat on the shaft with two set screws works fine for this load. My secondary chain front sprocket is held in place that way. But, set scres can loosten up, while a pin won't.
Matt
recumbent
100 kW
In a nutshell, RC motors are wonderfull... but after 5 pages discussing pulleys, chains and keyways,
It's reliability, and cost that keep us from choosing RC motors to run our E-bikes.
It's reliability, and cost that keep us from choosing RC motors to run our E-bikes.
safe
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Well... it's the fact that there is no easy to buy "package" that's holding people back right now. Once perfected and marketed this will make the alternatives look really lame, but for now we have our "hero's" like Recumpence that have the high tech machining tools necessary to give us a vision of the future.recumbent said:
If you are not a pioneer... just forget RC motors for now... but keep your eyes open because from the technical standpoint this is a big advance.
safe
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Low Cost, Low Tech, Approach...
Here's an idea for the "Do It Yourselfers".
First of all you will need a drill and a grinder and probably a welder.
Second you need to go to a motorcycle junk jard and find the transmission off of a small 50cc or 80cc motorcycle. You extract those gears and find a set that look to be about the right size for your needs. (cost $5? or free if you have something laying around already)
Third you buy precision bearings that match the gears you got or maybe even take the bearings too. Small motorcycles spin at about 8,000 rpm anyway and they use several horsepower so the bearings and gears are plenty strong.
Finally, figure out how to sandwich everything between two plates of metal and figure out ways to drill holes here and there to cut the weight. Steel is easily weldable, so that's my choice, but you could also go with aluminum. Steel is nice because if you screw up on something you can just weld over it and start over. But in the end you have an essentially zero cost geardown.
I'm sure people can think of other ways... in fact... go ahead and throw out your "Do It Yourself" ideas.
Here's an idea for the "Do It Yourselfers".
First of all you will need a drill and a grinder and probably a welder. Second you need to go to a motorcycle junk jard and find the transmission off of a small 50cc or 80cc motorcycle. You extract those gears and find a set that look to be about the right size for your needs. (cost $5? or free if you have something laying around already) Third you buy precision bearings that match the gears you got or maybe even take the bearings too. Small motorcycles spin at about 8,000 rpm anyway and they use several horsepower so the bearings and gears are plenty strong. Finally, figure out how to sandwich everything between two plates of metal and figure out ways to drill holes here and there to cut the weight. Steel is easily weldable, so that's my choice, but you could also go with aluminum. Steel is nice because if you screw up on something you can just weld over it and start over. But in the end you have an essentially zero cost geardown.I'm sure people can think of other ways... in fact... go ahead and throw out your "Do It Yourself" ideas.
TylerDurden
100 GW
Done any R/C pioneering yourself, safe?safe said:
Comparison of power ratings between HTD and (PG)GT3
[Ref: http://www.cnczone.com/forums/showthread.php?t=23291 ]
Atlanta HTD 5M timing belt (width = 9mm; 28 teeth small pulley) @ 1000rpm => 483W
Gates PowerGrip GT3 5M timing belt (width = 9mm; 28 teeth small pulley) @ 1000rpm => 787W
Quite a difference....... seems too much, even - think I'll check it....
[Ref: http://www.cnczone.com/forums/showthread.php?t=23291 ]
Atlanta HTD 5M timing belt (width = 9mm; 28 teeth small pulley) @ 1000rpm => 483W
Gates PowerGrip GT3 5M timing belt (width = 9mm; 28 teeth small pulley) @ 1000rpm => 787W
Quite a difference....... seems too much, even - think I'll check it....
safe
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Pre-Packaged Geardown Products
Not a "Do It Yourselfer?"
That's okay... if you have money to spend you can buy most anything. How about this?
http://www.harmonicdrive.net/products/gearheads/csf-unit/
List of Features
Space-saving, cost-efficient, etc. ... Satisfying demand for features such as these, CSF series harmonic drive gearheads are the solution in an industry where technological innovations are being achieved at an accelerated pace. Please select the unit that most suits your needs from the 12 different sizes we offer.
Simple and compact configuration
Direct load on the input section is made possible with built-in cross roller bearings
High torque capacity
High rigidity
Backlash-free
High positional accuracy and high rotational accuracy
High efficiency
Smoothness of operation
Coaxial input and output
1. Name of Model : CSF Series
2. Size : 14,17,20,25,32,40,45,50,58,65
3. Gear Ratio : 30, 50, 80, 100, 120, 160
Not a "Do It Yourselfer?"
That's okay... if you have money to spend you can buy most anything. How about this?
http://www.harmonicdrive.net/products/gearheads/csf-unit/
List of Features
Space-saving, cost-efficient, etc. ... Satisfying demand for features such as these, CSF series harmonic drive gearheads are the solution in an industry where technological innovations are being achieved at an accelerated pace. Please select the unit that most suits your needs from the 12 different sizes we offer.
Simple and compact configuration
Direct load on the input section is made possible with built-in cross roller bearings
High torque capacity
High rigidity
Backlash-free
High positional accuracy and high rotational accuracy
High efficiency
Smoothness of operation
Coaxial input and output
1. Name of Model : CSF Series
2. Size : 14,17,20,25,32,40,45,50,58,65
3. Gear Ratio : 30, 50, 80, 100, 120, 160
safe
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My Unite motor is rated at 3.2Nm at 1000 watts.Miles said:
But you are right... maybe the next product up would be better: (just to give a safety buffer)
http://matexgears.thomasnet.com/viewitems/all-categories/lgu-75-s?&forward=1
71 lb-in - 110 lb-in.
210 grams
safe
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I'm starting to think we are all in amazement at Recumpence's belt drive when the planetary option might not be as unrealistic as we thought. If you can buy a planetary geardown for a reasonable price and it only weights less than a pound then the RC motor solution might not be so hard after all.
Hmmmmm... have you (Miles) found a price anywhere?
Are they $50, $100, $300?
Hmmmmm... have you (Miles) found a price anywhere?
Are they $50, $100, $300?
safe
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This model looks nice:
Maximum Torque 180 kg-cm
Maximum Torque 157 lb-in.
Actual Reduction Ratio 7:1
Moment of Inertia 4.49 kg-cm2
Weight 294 grams
http://matexgears.thomasnet.com/item/all-categories/lgu-75-m/7mld?&seo=110&bc=100|3001006|3001009
This pretty much solves the problem... just what we want...
(now how much are they?)
Maximum Torque 180 kg-cm
Maximum Torque 157 lb-in.
Actual Reduction Ratio 7:1
Moment of Inertia 4.49 kg-cm2
Weight 294 grams
http://matexgears.thomasnet.com/item/all-categories/lgu-75-m/7mld?&seo=110&bc=100|3001006|3001009
This pretty much solves the problem... just what we want...
(now how much are they?)
safe
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Yeah... that's true. No matter what you will need to adapt whatever you get to fit it to the RC motor and at almost 10:1 geardown that's pretty good.Miles said:
I think that anything above about 95% efficiency is "good enough" because with the higher baseline of efficiency of RC motors to begin with and the WEIGHT savings it makes it all worth while. Saving weight is the focal point about this anyway since you can always get raw power from "Big Iron".
Also, if you mate the motor to gears you do get that "real world" advantage of 25/25/33 (25% more power, 25% better efficiency, 33% less heat) if you think in terms of going up and down in speeds. Only in the unrealistic "steady state" condition can you think of efficiency based on peak efficiency alone.
So when you add up all the plusses together the combined effect is much more than the simplistic formula alone. (as has been said many times before :wink: )
dirty_d
10 kW
http://www.cyclone-usa.com/sc_images/products/301_large_image.gif, well there is one problem out of the way, i guess thats a 5/8" bore with a keyway, so you could easily mount that on the jackshaft without modifying anything.
rkosiorek
100 kW
The Cyclone uses a 20mm Bore. 0.787 inch diameter.
rick
rick
safe
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For what I had in mind I'd do things a little differently though.
I want to go 114 to 14 using a #35 chain so that the pedal sprocket would amplify it's rpm up to about 1000. Then the motor rpm of 10,000 rpm gets dropped to 1000. Now the two are running at the same peak rpm which means that your natural pedal cadence and the motor powerband are in alignment. If you don't do that they could be so incompatible as to make it all worthless. After taking that 1000 rpm from the pedals and motor you send that back to the rear wheel and using a multispeed hub you can get a wide spread of either hill climbing ability or top speed.
It's starting to look like there might be ways to do this without needing the machining capabilties of Recumpence (no disrepect because that's great stuff) and being able to do it mostly on your own.
The RC motor will be on my #004 which at this rate could be a year or two away. (I've got to get #002 and #003 done first
) It seems that every time you take a step up in complexity you have to add about six months to the project. And this being a "hobby" and not a formal "job" I don't always want to work long hours on it.
I want to go 114 to 14 using a #35 chain so that the pedal sprocket would amplify it's rpm up to about 1000. Then the motor rpm of 10,000 rpm gets dropped to 1000. Now the two are running at the same peak rpm which means that your natural pedal cadence and the motor powerband are in alignment. If you don't do that they could be so incompatible as to make it all worthless. After taking that 1000 rpm from the pedals and motor you send that back to the rear wheel and using a multispeed hub you can get a wide spread of either hill climbing ability or top speed.
It's starting to look like there might be ways to do this without needing the machining capabilties of Recumpence (no disrepect because that's great stuff) and being able to do it mostly on your own.
The RC motor will be on my #004 which at this rate could be a year or two away. (I've got to get #002 and #003 done first
) It seems that every time you take a step up in complexity you have to add about six months to the project. And this being a "hobby" and not a formal "job" I don't always want to work long hours on it.
safe
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19,000 rpm?
I watched a little of the Formula One car racing (on tv) in Canada today and those motors rev to 19,000 rpm. Now it makes me think that if they can pull off 19,000 rpm with a lot more mass to worry about that it must be possible to be able to pull 19,000 rpm on an ebike.
If you are going to use a geardown it seems like the differences in efficiency between one ratio and the next is not so significant compared to the weight. And if you can run the motor at really high rpms (higher voltage) then you can cut down on the amps required and that means less heat.
Anyway... for the same reasons that a 1.0 liter "Normally Aspirated" Formula One motor can produce 900 horsepower one should be able to apply the same logic to electric motors.
The question of efficiency is minor compared with the power-to-weight ratio... a very small motor running at 19,000 rpms (and not flying to pieces) could generate the same power as some massive hub motor plodding along at 400 rpms.
Weight (in this case) trumps efficiency.
I watched a little of the Formula One car racing (on tv) in Canada today and those motors rev to 19,000 rpm. Now it makes me think that if they can pull off 19,000 rpm with a lot more mass to worry about that it must be possible to be able to pull 19,000 rpm on an ebike.
If you are going to use a geardown it seems like the differences in efficiency between one ratio and the next is not so significant compared to the weight. And if you can run the motor at really high rpms (higher voltage) then you can cut down on the amps required and that means less heat.
Anyway... for the same reasons that a 1.0 liter "Normally Aspirated" Formula One motor can produce 900 horsepower one should be able to apply the same logic to electric motors.
The question of efficiency is minor compared with the power-to-weight ratio... a very small motor running at 19,000 rpms (and not flying to pieces) could generate the same power as some massive hub motor plodding along at 400 rpms.
Weight (in this case) trumps efficiency.
rkosiorek
100 kW
sure and the Formula one motor will be junk by the end of the race. they have probably junked 2 motors already in the practice sessions for this weekend.
these motors will be returned to the manufacturer, the electronics stripped off and the rest will be scrapped.
but hey it does make 900 ponies for a little while anyway.
rick
these motors will be returned to the manufacturer, the electronics stripped off and the rest will be scrapped.
but hey it does make 900 ponies for a little while anyway.
rick
vanilla ice
1 MW
Actually an engine has to last 2 races now, otherwise they get a 10 place penalty on the grid. Not that this point invalidates your argument. Some other things may do tho...
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