My RC Mid Drive with Single Stage Reduction

Discussions related to motors other than hub motors.
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Re: My RC Mid Drive with Single Stage Reduction

Post by FZBob » Nov 15 2018 2:41am

Uturn wrote:
Nov 15 2018 1:04am
Could a belt drive be lower noise lower maintenance? Or will that assembly take too much space? Or no big pulleys available?
All very good questions!

Can you suggest a source for components? I would be curious to see how belt drives compare to chains with regard to cost, width, availability, etc.

One of my motorcycles has a belt (Buell Lightning). It came with a bunch of shielding to keep pebbles out of the mesh, as that could theoretically break the belt. It was ugly, so I took it off and never had a problem - possibly just lucky.

I went with the quick and dirty solution. Chains are very tolerant to all kinds of abuse - dirt, misalignment, sprocket runout, loosness, etc. Also, on a prototype build they are easy to shorten/lengthen when I make changes.

The drive is actually fairly quiet. When I chat with my riding partner on long uphills, the motor and chain noise are pretty much in the background, not too much louder than the gravel crunching. Over 8-10 MPH, the wind is louder.

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Re: My RC Mid Drive with Single Stage Reduction

Post by FZBob » Nov 16 2018 2:55pm

FZBob wrote:
Nov 11 2018 3:46pm
I received the Alien 5065 120KV motor on Friday. Half the weight of my favorite motor. In "theory", the Alien should make close to the power of the big Turnigy... We'll see...
Ride.jpg
I did two rides around my standard loop using the little Alien 5065 120KV motor. Compared with my big motor, the little Alien felt weak. Below about 150 watts, it felt OK. Over 150 watts, the watt meter numbers went up, but output didn't seem to increase. I saw a max of 319 watts, but it felt about half as strong as the big motor. This motor would NOT have made it up the big 22% grades from last week's ride. Also, chain noise was much louder with this motor using the same chain & sprockets... I put the big motor back on, and the noise went back down. Alien advertised weight 380 gm, actual 437 gm.

I'm now waiting for the E-Power Hobby 6354 60KV Motor, which I will try at 6S. If it works, I think I can shave 2/3 lb, and run an 11T or 12T motor sprocket, up from the 9T. Again, We'll see...

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Re: My RC Mid Drive with Single Stage Reduction

Post by SlowCo » Nov 16 2018 4:44pm

Great that you keep developing and trying new motors. :thumb:

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Re: My RC Mid Drive with Single Stage Reduction

Post by Kepler » Nov 17 2018 2:07am

FZBob, I think you are coming to the same conclusions I came to a couple of years ago. Bottom line there is no substitute for lots of copper.

I have cupboard full of motors I have tested over the years. Conclusion was that if you want those Watts to translate to the ground, bigger was always better. As far as a compromise was concerned though, 6354 was a good mix of usable power and weight. I have been watching your testing with interest because you are using much lower kv motors then I did. However, it seems the results are still very similar. I have been hoping there would be 50mm motor that would cut it power wise and noise wise. So far your testing (and mine) would suggest no such luck. Hopefully the E-Power Hobby 6354 60KV Motor will be a keeper. It does look good on paper. I look forward to the results on this one.
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Re: My RC Mid Drive with Single Stage Reduction

Post by ScooterMan101 » Nov 17 2018 1:50pm

Bought from a Company E-Power Hobby , in Florida U.S.A. ?
Kepler wrote:
Nov 17 2018 2:07am
Hopefully the E-Power Hobby 6354 60KV Motor will be a keeper. It does look good on paper. I look forward to the results on this one.
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Re: My RC Mid Drive with Single Stage Reduction

Post by FZBob » Nov 17 2018 4:02pm

ScooterMan101 wrote:
Nov 17 2018 1:50pm
Bought from a Company E-Power Hobby , in Florida U.S.A. ?
Just received a new toy!
E-Power Motor.jpg
E-Power Motor.jpg (103.01 KiB) Viewed 1639 times
Advertised weight 558 gm. Actual 545 gm.

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Re: My RC Mid Drive with Single Stage Reduction

Post by FZBob » Nov 17 2018 4:33pm

Kepler wrote:
Nov 17 2018 2:07am
FZBob, I think you are coming to the same conclusions I came to a couple of years ago. Bottom line there is no substitute for lots of copper.

I have cupboard full of motors I have tested over the years. Conclusion was that if you want those Watts to translate to the ground, bigger was always better. As far as a compromise was concerned though, 6354 was a good mix of usable power and weight. I have been watching your testing with interest because you are using much lower kv motors then I did. However, it seems the results are still very similar. I have been hoping there would be 50mm motor that would cut it power wise and noise wise. So far your testing (and mine) would suggest no such luck. Hopefully the E-Power Hobby 6354 60KV Motor will be a keeper. It does look good on paper. I look forward to the results on this one.
Yup, that's exactly what I'm seeing!

Interestingly, 25 years ago I was into high end audio, and amplifiers were the same way. Heavier tended to sound better. I still have some 70lb monoblock tube amps. Big transformers!

I'm curious to see if I can replace Weight with Volts. My current reference ("Big Orange") is 125KV, weighs 781 gm, and runs really well on 4S with a 9T motor sprocket. The E-Power 6354 is 60KV, weighs 545 gm, and I plan to try it with 6S and an 11 or 12T motor sprocket. Close to 2/3 the weight, and 3/2 of the voltage. (I'm going to try to restrain myself from trying 8S and 9T...)

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Re: My RC Mid Drive with Single Stage Reduction

Post by SlowCo » Nov 17 2018 5:14pm

FZBob wrote:
Nov 17 2018 4:33pm
(I'm going to try to restrain myself from trying 8S and 9T...)
No restraining please :mrgreen:

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Re: My RC Mid Drive with Single Stage Reduction

Post by FZBob » Nov 18 2018 2:00pm

I pulled the new 60KV motor apart to drill & tap the shaft. I thought some of you might be interested in seeing all the winds of fine wire.
E-Power Motor Windings.jpg
E-Power Motor Windings.jpg (226.68 KiB) Viewed 1597 times
Also, note that the bearings are shielded, NOT sealed. This appears to be very common. This motor and the three Turnigy motors are advertised for skateboards, and I suspect that eventually dust will get in and ruin the bearings. I wish the manufacturers would use sealed bearings on motors that operate in dusty conditions. I plan to switch to sealed bearings from Boca Bearings when mine wear out. Almost all Mountain Bike bearings are sealed...

The three Turnigy motors are closed, and have some degree of overlapping shielding over the can, probably to keep dirt out. The Alien and e-Power motors are VERY open. Probably better for cooling, but I'm concerned about dirt.

Bonus points for anyone who can identify why I thought I ruined this motor after reassembly! Hint - the motor is fine...

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Re: My RC Mid Drive with Single Stage Reduction

Post by SlowCo » Nov 18 2018 4:46pm

FZBob wrote:
Nov 18 2018 2:00pm
The three Turnigy motors are closed, and have some degree of overlapping shielding over the can, probably to keep dirt out. The Alien and e-Power motors are VERY open. Probably better for cooling, but I'm concerned about dirt.
Why not close of the openings of the motor and use Statorade/ferrofluid to compensate for the reduced air cooling?

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Re: My RC Mid Drive with Single Stage Reduction

Post by Animalector » Nov 18 2018 5:24pm

Shorted phase wires.. you went to turn it but it wouldn't turn. So you thought it was stuffed. But it wasn't...

Andy

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Re: My RC Mid Drive with Single Stage Reduction

Post by FZBob » Nov 18 2018 6:03pm

Animalector wrote:
Nov 18 2018 5:24pm
Shorted phase wires.. you went to turn it but it wouldn't turn. So you thought it was stuffed. But it wasn't...

Andy
Bingo! Gave me a good scare. I took it apart and reassembled it three times before I noticed.

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Re: My RC Mid Drive with Single Stage Reduction

Post by ScooterMan101 » Nov 19 2018 12:47am

How did you short the Phase wires ?

Pictures of what they looked like after shorting ?
and
Fixing ?
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Re: My RC Mid Drive with Single Stage Reduction

Post by neptronix » Nov 19 2018 1:05am

Looks line a nice motor from here. Any idea what the lamination thickness is?

Looks like if you ran 10s, youd be at around 1800rpm loaded, which would be fantastic for a direct to rear drive At a 4.25:1 rear ratio.. my guess is that the only way to match pedaling cadence in a single stage would be in 5s territory or maybe 4s.

Whats the plan?
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Re: My RC Mid Drive with Single Stage Reduction

Post by FZBob » Nov 19 2018 1:02pm

ScooterMan101 wrote:
Nov 19 2018 12:47am
How did you short the Phase wires ?
I cleverly stuck all three ends in a hole on my metal test bracket to keep them out of the way. You can see it in the pic. When I tried to turn the motor, it totally felt like it was submerged in super thick molasses. Very weird feeling. I thought I had bent the shaft or fried the bearings! It's really surprising how strong the braking force is!

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60KV preliminary results

Post by FZBob » Nov 19 2018 2:14pm

I have good news and less good news.

My goals for the 60KV experiment were to save some weight (320 gm) with a lighter motor and light 6S pack (https://hobbyking.com/en_us/turnigy-500 ... ttery.html - looks like very high energy density) and go from the 9T sprocket to a 11T for less noise.

Good news. I was really lucky when I picked the original motor for this project!

Less good news. The 60KV motor was really weak on 6S. It would barely pull 160 watts. I rigged up 8S, and went back to the 9T sprocket, and it performed similar to the 125KV Turnigy (Big Orange), except not quite as good, since it is a lighter motor.
8S.jpg
8S.jpg (121.13 KiB) Viewed 1516 times
Preliminary conclusions - Changing KV works like a transformer. I cut the KV in half, and had to double the Voltage to get half the Amps, and therefore the same power. All the guys who do the math will have a good chuckle over this revelation. :mrgreen:

I was hoping to trade more Volts for less Weight, but that's not happening. All I got was a sideways move - Volts for Amps.

It looks like at a given reduction, Power is pretty much proportional to Weight (as Kepler mentioned).

The other option would be to increase the reduction ratio, and spin a small light motor faster. However, with single reduction, I'm at a hard limit of 10:1. I could do a double reduction, and I have done some gearbox layouts in CAD, but the added weight of the gearbox plus a freewheel would put me right back to where I am now...

I may consider an 80KV 6354 size motor on 6S (with a small hit on power) in the future, as I would really like to save that 320 gm... But I may have to wait a bit, as my wife is asking questions. She says these all look the same!
Motors 5.jpg
Motors 5.jpg (176.45 KiB) Viewed 1516 times
Back to the good news. The bike with the big motor puts a smile on my face every time I ride it! :)

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Re: My RC Mid Drive with Single Stage Reduction

Post by neptronix » Nov 19 2018 3:02pm

Yeah, you learned the hard way that more volts doesn't make more power. It's all about the watts.

I did the math on a rear drive last night and decided that with a single stage, you really want 10S and a reduction ratio that puts the continuous speed around half of the 'maximum power' - but probably less than that..

IE the ideal motor for a direct rear drive with a single reduction would be an 80mm version of the last motor you bought.
Which puts you roughly at the size/weight of motors used in common mid drives, but you can skip the extra complexity and weight of the second stage. So it still beats hubs in power density theoretically.

Put the same motor in a single reduction mid and you gotta run 4-5S and cut your expectations down a lot for the crank power.

If you gotta stick to a single reduction, you need a pretty large motor.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

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Re: My RC Mid Drive with Single Stage Reduction

Post by neptronix » Nov 19 2018 3:08pm

Here's an idea for a lightweight mid drive..
How about a Bafang G310 fast winding?

That motor is 5.6lbs and has an 11:1 reduction inside already.
Continuous power in a motor wheel is around 700W. Could possibly do >800W if you spin it to 400rpm, which would be easy to reduce to the crank.

Take a front motor.. shave the shell.. cut the extra off the axle.. run a chain.. probably ends up at 7lbs and you effectively have something more powerful than a Bafang BBS02 at a pound less weight... plus, no pedal offset that the bafang drives have.

Otherwise, dual reductions seem to be the way forward for lightness, even if the first stage is only 3:1.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500.
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Re: My RC Mid Drive with Single Stage Reduction

Post by andrea_104kg » Nov 20 2018 1:33pm

Add to the motor a simply and not expensive gear?
http://www.petrolscooter.co.uk/gearbox- ... okart.html

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System Weight

Post by FZBob » Nov 20 2018 3:46pm

Just for fun, I decided to post part of my weight spreadsheet. These are actual weights. I was really surprised by all the extra stuff that is usually forgotten, it sure adds up... My current setup is Column 4 - Big Motor, No Freewheel, 8Ah battery.

Note how heavy my old cyclone setup was!
Weight.jpg
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Bill of Materials

Post by FZBob » Nov 22 2018 3:47pm

I have 420 miles and 40,000 feet of climbing on my build at this point. So far it has been very reliable and fun. The chain has only stretched 0.6%. Since the configuration appears to be stable, I have decided to post my Bill of Materials. I'm a bit surprised at how inexpensive it is.
E-Bike BOM.jpg
E-Bike BOM.jpg (99.19 KiB) Viewed 1401 times
The parts which need to be modified are:
Motor Sprocket - File out "D" section, File Keyway. 15 minutes with a round file and a square jewlers file.
Motor shaft spacer tubes - May need cut to length.
Motor Mount Rivet Nuts - I installed three Rivet Nuts in the bike frame (scary :shock: ). These appear to be exactly the same as Giant uses for water bottle mounts, and they seem to work very well. I used a Hose Clamp at the front of the mount just to keep the torque reaction from lifting up on the front bolt. If the motor is mounted under the frame, the hose clamp should go at the rear of the mount. (I would not use rivet nuts in a Carbon frame...)
Motor Mount - Angle Aluminum. Cut to length, with tongue for the hose clamp. Slot one face for the motor. Drill to match inserts in bike frame. Fab a support strut which extends to bottom of frame. If anyone is interested, I can post my drawing. My motor slots would be correct for this motor, but the bicycle interface would probably need to be modified for individual applications. This could be done with hand tools in a day (coping saw), or maybe have a machine shop do the slots.
Wiring - Same as any other build...

I have noticed an Unintended Consequence. I had never planned to go fast uphill, but I'm finding that 350-400 watts and some serious pedaling and I can rip uphill singletracks. This is very addictive!

It rained yesterday here in NorCal, so the air is clear and the Hero Dirt has arrived. I'm off for a Thanksgiving ride! :D

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Reducing Chain Noise

Post by FZBob » Dec 09 2018 2:03pm

The main source of noise on this build is the chain meshing with the 9 tooth motor sprocket. It's not bad, but I would like it to be almost silent.
O-Rings.jpg
O-Rings.jpg (130.57 KiB) Viewed 1117 times
To that end, I bought some O-rings...

Anyone care to guess the plan?

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Re: My RC Mid Drive with Single Stage Reduction

Post by SlowCo » Dec 09 2018 2:13pm

An O-ring on either side of the motor sprocket where the side plates of the chain will rest on?

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Re: My RC Mid Drive with Single Stage Reduction

Post by FZBob » Dec 09 2018 2:34pm

SlowCo wrote:
Dec 09 2018 2:13pm
An O-ring on either side of the motor sprocket where the side plates of the chain will rest on?
Well that was quick!
)-Rings CAD.jpg
)-Rings CAD.jpg (33.22 KiB) Viewed 1115 times
I'm hoping the O-rings will cushion the chain as it slaps down onto the sprocket. It will be interesting to see if it works.

I have some concerns about sensitivity to the amount of O-ring compression. Durability will also be a big question. We'll see...

Also, any other suggestions to quiet chains would be appreciated!

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Re: My RC Mid Drive with Single Stage Reduction

Post by larsb » Dec 10 2018 12:38pm

I guess you could buy an o-ring chain :D
Ride on :D

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