Resurrecting an Ultra Motor A2B Metro with 20S power

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Resurrecting an Ultra Motor A2B Metro with 20S power

Post by edamame » Sep 05 2012 3:24pm

Hey y'all,

After reading a bunch here I went and bought a broken Ultra Motor A2B Metro off of Craigslist a few months ago. The previous owner ran over something in the road that got wrapped up in the rear hub and it shorted out a new motor he had only had for a month or so. I watched it sit on Craigslist for a while while I was doing research so after about a month I went up to Austin to check it out. I ended up buying it for $500 which I thought was a good deal for a bike that I wouldn't have to reengineer everything to ride electric. Lucky me, it also had the secondary battery.

I took off the rear wheel and could see where the ground wire had ground out and shorted out against the axle so I pulled the tire and stripped the spokes off to pull the case halves of the motor apart. This is what I saw:

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I planned to turn this into a quasi-legal 40mph scooter so I removed the 36v motor controller by taking out the mounting screws and cutting the pins for the three hall senders. I wired the three phase wire pairs to 12 AWG THHN wire with the help of a local motor builder (John at Massengale Armature Works-Thanks!).

Here it is ready to go back together:

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I used heat transfer epoxy to glue in a thermocouple to the windings to keep tabs on motor temp:

Image

The 12 AWG wires were as big as I could go:

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So I had a friend help me push the aluminum case halves together with a press and I tested it with a Crystalyte 40A Sensorless controller from Ebikes SF. It worked! So I had the wheel rebuilt with the stock parts. I bought an extra stock torque arm since the stock A2B only comes with one which is dumb!

Because I planned on going almost twice as fast as stock I bought new front and rear BB7 brakes with 205mm in front and 185mm in back:

Image

After riding for a couple of weeks at 20S (80-84v) I found the stock mild steel torque arms were as soft as lead:

Image
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Here's a stock torque arm on the right with 100 miles on it compared to my laser cut SS version with 600 miles on the
left:

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I put 1 torque arm on the outside of each dropout in the stock location and two on the inside on the cluster side (4 total) to replace a 1/4" thick aluminum spacer. Overkill!:

Image

Here's a pic of the early times when I was running the front and rear stock battery in series. You can see my data logger for motor temps on the rear rack:

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I bought four HK 10S 5800mah stick pack RC Lipos (20S, 2P) and stuck them in an empty rear battery case:

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I charge them only on solar power:

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The bike has been pretty much bulletproof. My work is 2.3 miles from home and so on most days I ride 9.2 miles. People try to kill you in San Antonio if you drive too slow so I run about 35-38 mph on the busy stretch which is only 1/2 mile of the 2.3 miles. I like to pass cars! At top end the bike is pretty much tapped out handling wise.(Edit: I fixed the handling by moving the batteries mid-ship.) I have a Fox float RP23 rear shock with 275 pounds of air pressure in it and it is not enough to keep the rear wheel from hitting the bottom of the battery case on big dips so I pick my butt off the saddle when those come along.

The stock batteries did work at 20S/72 volts but after getting the 21Ah of RC Lipos I cannot go back. The BMS on one of the stock batts would cut out if I asked for too much throttle at a time which was annoying. The RC Lipos don't do that but they will stutter if I ask too much of them. As for motor winding temps, the most I have see was 227F a week ago with 100F ambient and I was pushing it as hard as it would go. (Average temps on my way to work and back are about 125-150F.) A guy in an Alfa passed me barely and at the next light I asked him how fast his speedo said I was going--40mph slighly downhill. My cycle analyst is not yet programmed correctly for shunt value so my numbers are off. The bike works though and when the weather cools off I'll fix the little things.

I bought a new seat, the Forte Easy Rider from Performance bike and I like it alot. I enjoy riding to work even in this infernal heat. I'll like it even more when the weather cools back off.

Anybody wanna know any details not mentioned here?
Last edited by edamame on Jun 08 2019 11:01pm, edited 4 times in total.

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by salty9 » Sep 05 2012 7:03pm

Looking good. Details on charging would be interesting.

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by edamame » Sep 05 2012 7:38pm

salty9 wrote:Looking good. Details on charging would be interesting.
Thank You.

Here is my thread on solar charging: http://endless-sphere.com/forums/viewto ... 14&t=41991

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by mr.pibb » Sep 16 2012 10:00pm

Hello edamame. Awesome info!

I have a a2b velociti 26. It has a dead battery so I am trying to get it going on SLA because I dont have $800 to sink into a new battery.
I am a little confused as to how my bike works. I started a new post with a wiring diagram.

What I cant understand is the battery leads go straight to the motor on my bike and not through the controller first.
How many wires go into your motor?-- the 2 power leads and 4 or 5 other wires?

My contoller is powered by 2 additional leads from the battery off the bms.
I suspect there is a controller of some type along with the bms inside the battery housing.

I want to try and hook up the (3) 12V SLA to the motor and run the 2 power leads to the controller and see if it works...
However, I am concerned because if I am right the sla battery should throw full amps at the motor: if there's nothing limiting it...

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by mr.pibb » Sep 17 2012 2:14am

OK-- so now I think I understand the controller is in the hub correct?

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by t3sla » Sep 17 2012 3:54am

nice work with the torque arms, everyone should routinely inspected their DIY bikes for this exact reason 8)
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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by fechter » Sep 17 2012 8:27am

Nice work!

What did you have to do to get the motor apart?
"One test is worth a thousand opinions"

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by pdf » Sep 17 2012 9:23am

Awesome find! And a great job repairing/upgrading.
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Giant Boulder 9C 8x8, 48v, 10 Ahr LiMn from ebikes.ca

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by Ypedal » Sep 17 2012 9:37am

Great work, and finally someone took good pictures of the process, 8)

A " How To " on opening the motor and closing it back up would be awsome, i'm about to do the same to my A2B for 2013..

Steering must be really fun at 40mph... she's steep..... ( ok at 20 mph ... but just barely )

So the motor is working well with sensorless?.. good power off the line, no soft start.. ?
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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by mr.pibb » Sep 17 2012 12:15pm

Ok I wanted to go the cheapo route and go sla for my a2b velociti. I know know.... :roll:
But I liked what you did with the (4) 5800mah stick pack RC Lipos in the old case
How much did that run you with the charger?
That icharger wasnt able to fit inside the case too was it?
Did you use bms? Im sorry Im new to lithium...

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by fechter » Sep 24 2012 9:23pm

I keep looking at those pictures of the motor insides. That is a very interesting design. I don't think I've seen any other big motors that use ferrite cores. This should really lower the core losses, which could be significant on a big hub motor. The way they're attached to a big aluminum ring inside should help a lot with heat dissipation. It wouldn't be too hard to adapt to water cooling or internal air cooling.

I don't know if you could tell, but I wonder what holds the winding cores on? It looks like they're just glued on. It would have to be some pretty good glue to not let go, especially when it gets hot. It would probably be better if there was some kind of mechanical fastener holding them on.
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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by edamame » Sep 24 2012 10:44pm

mr.pibb wrote:OK-- so now I think I understand the controller is in the hub correct?
Yes, it is inside the hubmotor. -Jim

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by edamame » Sep 24 2012 10:48pm

fechter wrote:Nice work!

What did you have to do to get the motor apart?
After I removed the spokes I used a 12" long 2x2 pine board and a ball peen hammer to tap one of the the halves away from the other little by little until it popped off. I did the same for the remaining case half so that I could replace bearing in that half, too. Just make sure that when you press it back together make sure to offset the spoke holes of one half against the other so they are not lined up.

I don't get notified when there is a reponse to this thread hence my delay in responding...

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by edamame » Sep 24 2012 10:53pm

Ypedal wrote:Great work, and finally someone took good pictures of the process, 8)

A " How To " on opening the motor and closing it back up would be awsome, i'm about to do the same to my A2B for 2013..

Steering must be really fun at 40mph... she's steep..... ( ok at 20 mph ... but just barely )

So the motor is working well with sensorless?.. good power off the line, no soft start.. ?
Motor works fine but this is my very first ebike so I have nothing to compare it to other than BMW motorcycles. Steering on the Metro at 37mph is "lively" but fine if you keep your hands on the bars. There is no soft start but the sensorless controller pretty much requires me to pedal for five feet to get things going before I apply throttle. Does not start well without pedaling first. -Jim

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by edamame » Sep 24 2012 10:58pm

fechter wrote:I keep looking at those pictures of the motor insides. That is a very interesting design. I don't think I've seen any other big motors that use ferrite cores. This should really lower the core losses, which could be significant on a big hub motor. The way they're attached to a big aluminum ring inside should help a lot with heat dissipation. It wouldn't be too hard to adapt to water cooling or internal air cooling.

I don't know if you could tell, but I wonder what holds the winding cores on? It looks like they're just glued on. It would have to be some pretty good glue to not let go, especially when it gets hot. It would probably be better if there was some kind of mechanical fastener holding them on.
I have another motor apart in my garage. I will take a look in the morning to try to answer your questions as an edit to this post. I'm not sure where you are seeing a big aluminum ring. The magnet ring on the periphery is steel. -Jim

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by edamame » Sep 24 2012 11:04pm

mr.pibb wrote:Ok I wanted to go the cheapo route and go sla for my a2b velociti. I know know.... :roll:
But I liked what you did with the (4) 5800mah stick pack RC Lipos in the old case
How much did that run you with the charger?
That icharger wasnt able to fit inside the case too was it?
Did you use bms? Im sorry Im new to lithium...
The charger was about $200 US and the batteries were about $520ish. I would never run with the iCharger onboard since I always charge on solar at home and the rear battery case is heavy just with batteries alone (17 pounds). I do not have a BMS. I bulk charge the 10S Zippys to 40V and discharge to 38V. I fully charge and balance them about once every other Saturday to make sure they last a while. The Zippys fit entirely inside the rear battery case. I will try to upload some more pics tomorrow.

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by fechter » Sep 25 2012 12:24am

Thanks. If you get another one apart, I'd love to see what the edge of the stator looks like.
It also appears you removed the stock controller guts somehow. How is that done? Looks to be potted in epoxy.

Bummer you have to remove the spokes to take it apart. At least it's only half of them. I'd suggest making mating marks on the cover before removing it so it can be put back exactly aligned.

One thought I had is if you made a hole in the aluminum (under where the controller used to be) and placed a fan over the hole, it would circulate air from one side to the other and force it between the windings along the way. This would greatly improve heat dissipation from the windings and move it to the casing, which can dissipate it to the outside. The fan could be powered by a small voltage regulator/rectifier attached to a pair of phase wires. Anytime the wheel moves above a certain speed, the fan runs and no additional wires are needed through the axle.
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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by fechter » Sep 25 2012 8:29am

edamame wrote: I have another motor apart in my garage. I will take a look in the morning to try to answer your questions as an edit to this post. I'm not sure where you are seeing a big aluminum ring. The magnet ring on the periphery is steel. -Jim
I'm not sure exactly what you'd call this part, but see the red arrow in the picture below. If cooling was applied to this part, it would have direct contact with the stator teeth from below and be able to carry away a significant amount of heat. The more I think about it, an air circulation approach would probably be a lot easier and effective.

I'm also still curious about the stator tooth material. I was wild guessing they are some kind of ferrite from the appearance in the pictures, but they could just be painted. I don't think they would be solid iron as this would have massive eddy current losses. Ferrite is very brittle and cracks easily. If one took a file to a corner and filed it, you could tell. Most motors use laminated iron. It could be something similar to powdered iron that's pressed.

Where did you get the stainless torque arms? There is probably a market for those. :idea:
Water cooling location.jpg
Water cooling location.jpg (92.8 KiB) Viewed 8766 times
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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by edamame » Sep 25 2012 2:18pm

fechter wrote:
edamame wrote: I have another motor apart in my garage. I will take a look in the morning to try to answer your questions as an edit to this post. I'm not sure where you are seeing a big aluminum ring. The magnet ring on the periphery is steel. -Jim
I'm not sure exactly what you'd call this part, but see the red arrow in the picture below. If cooling was applied to this part, it would have direct contact with the stator teeth from below and be able to carry away a significant amount of heat. The more I think about it, an air circulation approach would probably be a lot easier and effective. Like I mentioned before, on average I usually saw no more than 175F in the windings from my thermocouple and datalogger. Would it make that big of a difference to lower the temps? I saw 227F as a super max but I was trying to make it hot.

I'm also still curious about the stator tooth material. I was wild guessing they are some kind of ferrite from the appearance in the pictures, but they could just be painted. I don't think they would be solid iron as this would have massive eddy current losses. Ferrite is very brittle and cracks easily. If one took a file to a corner and filed it, you could tell. Most motors use laminated iron. It could be something similar to powdered iron that's pressed. I'll take a look tonight at my spare motor.

Where did you get the stainless torque arms? There is probably a market for those. :idea: I made 30 extra torque arms to sell if anyone needed them.
Water cooling location.jpg
Last edited by edamame on Sep 25 2012 2:25pm, edited 1 time in total.

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by edamame » Sep 25 2012 2:23pm

fechter wrote:Thanks. If you get another one apart, I'd love to see what the edge of the stator looks like.
It also appears you removed the stock controller guts somehow. How is that done? Looks to be potted in epoxy. The controller is attached to the aluminum inner hub with 3 Phillips screws and the 9 hall sender leads. I removed the screws and cut the leads to remove the controller.

Bummer you have to remove the spokes to take it apart. At least it's only half of them. To replace bearings you need to remove all spokes. It would be a pain to work on the motor with the rim attached. I'd suggest making mating marks on the cover before removing it so it can be put back exactly aligned. That's good advice for anyone separating the Metro/Velociti motor.
Last edited by edamame on Sep 25 2012 8:50pm, edited 1 time in total.

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by edamame » Sep 25 2012 2:29pm

I wish someone with a lot of ebike experience (like Guru class) could ride this thing. I wonder what they'd think of it and what could be done to make it better. I am forever wondering if I missed something obvious.

I always wonder about these things when I build them alone, without help. Anyone else feel that way?

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by edamame » Sep 25 2012 3:42pm

One funny story: A couple of months ago I was on the way home from a downtown round trip and on the last straight road before getting to my neighborhood I noticed I was being followed by a San Antonio cop so I went only 20 mph and used up my whole lane as I always do. I got into the left lane to turn into my neighborhood and he followed me and turned on his lights as we went through the intersection. I pulled over in the first side street and got off and took off my helmet. He turned off his lights and immediately told me I wasn't in trouble. He said he was a fellow cyclist and was just so damned curious about my bike that he just had to know more. So we talked for about 20 minutes and I told him what it could do speed-wise and we agreed there was quite a gray area as far as electric bikes were concerned. His major concern from a legal standpoint was whether I could take up a whole lane on a bicycle or not. I've always heard that bikes can take a lane if they so choose but in some cases it would not be advised since car drivers would kill you for holding them up. Anyways, it was an interesting conversation!

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by mr.pibb » Sep 25 2012 7:19pm

I believe my mounting is completely different but I may be interested in one of those torque arms anyway. Where they very expensive to manufacture?

I will be splitting my motor here by the weekend. If I can find a camera I will take more pics. I have taken off my spokes and marked them. Should they go back in the exact spots they came off of?

They all appeared bent at the nipple. Is this normal? It looked like they were supposed to be but Im not sure. Other than that they looked ok. Should I just replace them anyway since Im here or am I most likely good to reinstall?

Question about the thermocouple.. Did you only hook up a temp gauge or did you also put an over-ride swith to turn it off at a certain temp?

I cant wait to see inside! :mrgreen:

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by edamame » Sep 25 2012 7:47pm

mr.pibb wrote:I believe my mounting is completely different but I may be interested in one of those torque arms anyway. Were they very expensive to manufacture? Per piece they weren't too bad but I had to make a bunch to get the price down. I'd sell them for $20 each which is the same as a soft factory part. I recommend two per bike.

I will be splitting my motor here by the weekend. If I can find a camera I will take more pics. I have taken off my spokes and marked them. Should they go back in the exact spots they came off of? I would not worry about what exact spots the spokes came from.

They all appeared bent at the nipple. Is this normal? It looked like they were supposed to be but Im not sure. Other than that they looked ok. Should I just replace them anyway since Im here or am I most likely good to reinstall? Mine were slighly tweaked at the nipples, too. They are very short so they have to bend a little where they go into the nipples since the hub is 2" wide.

Question about the thermocouple.. Did you only hook up a temp gauge or did you also put an over-ride swith to turn it off at a certain temp? Just had a meter velcro'd to the down tube to get a visual on temps. My motor builder told me not to worry unless I saw 180C in the windings. Most I have seen is just under 110C pushing it hard. I recently removed the datalogger to keep it from getting stolen. Temps don't seem to be a problem with this setup. I never had any sort of logic circuit with the thermocouple. I wouldn't know how to make one anyway...

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Re: Resurrecting an Ultra Motor A2B Metro with 72 volt power

Post by mr.pibb » Sep 25 2012 9:33pm

Ok you said you were getting max temps of 110C. Are you running at the full 40A or only like half?
I will be also buying a controller probably this weekend too. Are you pretty happy with the crystlyte and data logging?
It seems like the best route to go from what I see.

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