A2B build

I picked up an A2B. It was a show room unit that has been collecting dust for several years. It's in pristine condition. The pack was run down pretty good, but recovered nicely. Geez these things are sloooooow and weak! Who in their right mind would EVER pay $2600 for a weak EV like this? Yeah it's a nice frame, but geez that's highway robbery! what's worse is the controller is inside the motor...that's just a failure waiting to happen!

The frames are super nice TIG welded aluminum and precision made with decent components. The back shock feels too soft despite cranking the tension screw. Maybe the gas cylinder has leaked? The front shocks are fine. I think I'll switch over to hydraulic brakes and replace the back shock but otherwise leave the components as is. The back dropouts are pretty weak, but OK for 500 watts. They will need reinforcing.

Other than a thick layer of dust the bike is perfect. There's zero wear on the tires. I bet it has less than 10 miles on it.

I pulled apart the back wheel and motor. That was a royal pain! You have to unlace the motor from the rim so you can pull the motor apart. It's 2 halves press fit together along the center line. You need a 3 jaw puller that can either hold to the brake rotor screws or around the spoke flange. The puller screw sits on the shaft end on the brake rotor side. Put some tension on the puller screw and then using a block of wood and hammer start knocking around the perimeter of the other spoke flange. The motor will give a disconcerting "POP" as the glue or just metal to metal bonding gives way. Apply a bit more tension and repeat. Slowly the 2 halves will migrate apart. Do NOT use puller force alone if you want to reuse the motor. That's a perfect way to break the cast aluminum motor shell! After about an inch of movement, the 2 motor halves are apart. I think it took an hour to unlace the motor from the wheel and 10 minutes to take the motor apart. I know Ultramotors is long gone, but I think they forgot about side access plates on hub motors! GRRR!

Once Ihad the motor apart I noticed the phases are 2 strands of 20 awg. This motor was wound to NEVER see more than 500 watts. With the factory wind over watting it might get you to 700 watts. I plan on rewinding the stator...there's lots of empty room on here. I'm thinking 60% full at most. The magnets are N40 or maybe N45 and LARGE. It seems like rewinding it ought get a serious wattage boost. The stator has .3mm lams. Other than the pathetic copper fill, it looks to be a decent motor design. I'm really curios to see what she will do after a copper rich rewind. Worst case a friend wants it for his weak e-bike. I'd be happy with 2-3kw out of this motor. It has 18 stators and 16 magnets. I have 2 of the hub motors. I might turn the other one into a 60 Kv outrunner.







I haven't checked it yet but I have a brand new 4kw QS hub. If it fits the drop-outs, it WILL look ridiculous with this monster in the back, but it ought to be quite quick too. It's a V3 so 4kw is just the starting place...probably more like 8kw peaks with 7kw continuous.

So...this motor...AND by the power of the EV gods, it WILL fit the drop-outs. I'll need to reinforce them no matter what. I might as well just lengthen the swing arms a little and create some width to accommodate the wider motor at the same time...hmmm...60mph+ on an A2b...should be interesting! That's more than 3X the factory speed and at least 8X the factory power. I bought this motor new a couple of years ago and then abandoned the project in favor of non-hub based builds. It's been sitting in it's box for the last 2 years. Might as well use it for something ridiculous.



On here...

Many shocks that are extremely cheap and coiled don't have oil dampers at all. Wouldn't be surprised at all.

Tommm said:

Many shocks that are extremely cheap and coiled don't have oil dampers at all. Wouldn't be surprised at all.

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It's an A2B...they tend to have decent quality components. It's probably not just a spring.

The stock shock on mine was just a spring with no damping. A real shock was a big improvement.
I’ve pushed mine to about 2.5kw with the stock windings. I can only get it to draw about 55A at 52v during takeoff. I think this is limited by the resistance.

ElectricGod said:

Tommm said:

Many shocks that are extremely cheap and coiled don't have oil dampers at all. Wouldn't be surprised at all.

Click to expand...

It's an A2B...they tend to have decent quality components. It's probably not just a spring.

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Never underestimate corporate greed.

fechter said:

The stock shock on mine was just a spring with no damping. A real shock was a big improvement.
I’ve pushed mine to about 2.5kw with the stock windings. I can only get it to draw about 55A at 52v during takeoff. I think this is limited by the resistance.

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Really?! 2500w...that's far more than I expected from 2 strands of 20 awg. Mine is already wired delta so I can't do that trick to lower phase resistance.

I'm sure rewinding it for more copper fill will help bump its wattage a good bit and lower phase resistance. It's not for lack of good magnets, just the windings. I know I can get more copper on it and not change the turns per tooth.

What shock did you use to replace the factory one? I think I probably have like you do...no damping at all.

ElectricGod said:

fechter said:

The stock shock on mine was just a spring with no damping. A real shock was a big improvement.
I’ve pushed mine to about 2.5kw with the stock windings. I can only get it to draw about 55A at 52v during takeoff. I think this is limited by the resistance.

Click to expand...

Really?! 2500w...that's far more than I expected from 2 strands of 20 awg. Mine is already wired delta so I can't do that trick to lower phase resistance.

I'm sure rewinding it for more copper fill will help bump its wattage a good bit and lower phase resistance. It's not for lack of good magnets, just the windings. I know I can get more copper on it and not change the turns per tooth.

What shock did you use to replace the factory one? I think I probably have like you do...no damping at all.

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The shock is a DNM that was in my junk pile from another scooter. The spring it came with was way lighter so I transplanted the stock spring, which is 1500lb/in. This was not easy, but worked. I looked for a shock with the right rate and length but couldn't find any.

With a 52v battery, I can run mine for pretty long stretches at 40A and it does well. I am using ferrofluid. It will overheat on long climbs off road where my speed is below 10mph. If I can keep the speed up, the air cooling is enough to keep it from overheating. I have a temp probe stuck to the windings.

fechter said:

The shock is a DNM that was in my junk pile from another scooter. The spring it came with was way lighter so I transplanted the stock spring, which is 1500lb/in. This was not easy, but worked. I looked for a shock with the right rate and length but couldn't find any.

With a 52v battery, I can run mine for pretty long stretches at 40A and it does well. I am using ferrofluid. It will overheat on long climbs off road where my speed is below 10mph. If I can keep the speed up, the air cooling is enough to keep it from overheating. I have a temp probe stuck to the windings.

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Thanks for the "shocking' image.

I've transplanted springs before...it can be a PITA!

10mph...OH GEEZ...definitely rewinding before I put up with that! Ferrofluid is against my religion...One leak in the shell and what mess!

I'll vent the side covers. I need to pull the stator just to get rid of the factory controller. I might as well open the shell up while I'm there. Paint the bare stator with electrical paint. Do a proper copper fill rewind. Maybe put a small EDF inside too for cooling. My bearings are crunchy...they need replacing despite being brand new.

The factory hub motor will get rewound this weekend.

I'm going to use 28 awg. It's easy to wind and that helps a lot. I know I can get more copper on the stator. I'm hoping for 40% more at least. Last rewind I did, I got 60% more copper on the stator by weight and that was from 20 awg (factory) to 28 awg (rewind).

20 awg is a lot better for maximizing the copper to insulation ratio, but it's lots harder to get tight winds with it. As a result, it's much harder to get that maximum copper fill that slightly thinner strands make easy at slightly less copper per strand.

All dampers need to be serviced with use. Even if it's not leaking the oil thins out after a while.

flat tire said:

All dampers need to be serviced with use. Even if it's not leaking the oil thins out after a while.

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OK...assuming I have a gas/oil filled shock...what kind of oil do you use? Will air compressor oil work?

No. You need a special oil with anti foaming additives. I would just buy fork oil (search it up on amazon). You can also use automatic transmission fluid but it may be thicker and give stiffer damping than you want.

ElectricGod said:

flat tire said:

All dampers need to be serviced with use. Even if it's not leaking the oil thins out after a while.

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OK...assuming I have a gas/oil filled shock...what kind of oil do you use? Will air compressor oil work?

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If it's the damper oil, it should be specific for the fork. If it's the bath oil in the lowers, then you have more flexibility (some people use Mobil 1).

Oils are NOT specific to your suspension, just pick a good damper oil with the correct weight. If you don't know the weight pick whatever and see how it performs. Your manual will tell you which one(s) to use.

Thanks guys...that was useful. I have shocks on stuff, just never thought about the oil inside before.

flat tire said:

Oils are NOT specific to your suspension, just pick a good damper oil with the correct weight. If you don't know the weight pick whatever and see how it performs. Your manual will tell you which one(s) to use.

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You may mean the correct viscosity, since for fork oil, the weights versus viscosity is all over the map between manufacturers. Yup, the owners manual is a good place to start and if you go with another brand oil, there's generally information available to determine the equivalent weight for that brand.

E-HP said:

flat tire said:

Oils are NOT specific to your suspension, just pick a good damper oil with the correct weight. If you don't know the weight pick whatever and see how it performs. Your manual will tell you which one(s) to use.

Click to expand...

You may mean the correct viscosity, since for fork oil, the weights versus viscosity is all over the map between manufacturers. Yup, the owners manual is a good place to start and if you go with another brand oil, there's generally information available to determine the equivalent weight for that brand.

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I got on Amazon and looked at fork and shock oil.
It seems that 5, 7.5, 10, 15 and 20 weight are common.
I have nooooo idea what's in the shock already...if anything...that may be why it's so soft.

Looking at this mechanically...
There's a long lever (swing arm) on that one smallish shock. Since it's really squishy right now. A thicker oil will produce a stiffer shock.
I'm thinking to help the shock as much as possible that I get some 10 or 20 weight.

I can make a comparison judgement easily enough. I know what 5 and 30 weight engine oil are like. While a different formulation, the viscosity of oils is a standardized thing. I should know pretty easily by feeling the shock oil with my fingers, what it's probable viscosity is now.

http://www.mediaturbo.com/clients/marzocchi/forkoilviscosity.html
http://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid

A2B look awesome. I want one!

looking at that shock, it doesn't look like an oil filled shock. In fact it looks more like the kind of "shock" that's really just a spring.

When you sit on the bike hard, does it bounce at all, or does it softly sag like sitting on a pillow? if there is any bounce or spring back, then it's likely not a real shock, but rather just a spring.

If it says KS 260 on the label at the tire end, then it's kind of just a rod in a tube with a spring attached. no dampening at all. not really a shock.

E-HP said:

http://www.mediaturbo.com/clients/marzocchi/forkoilviscosity.html
http://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid

Click to expand...

Thanks for that second link. I loved what they said about using motor oil to guesstimate the viscosity of shock oil...aka...don't bother.

Drunkskunk said:

looking at that shock, it doesn't look like an oil filled shock. In fact it looks more like the kind of "shock" that's really just a spring.

When you sit on the bike hard, does it bounce at all, or does it softly sag like sitting on a pillow? if there is any bounce or spring back, then it's likely not a real shock, but rather just a spring.

If it says KS 260 on the label at the tire end, then it's kind of just a rod in a tube with a spring attached. no dampening at all. not really a shock.

Click to expand...

YUP...KS-260...just a frigging spring.
Well that won't do at all!

Well...not quite as much done on the motor as I expected.

The motor controller is in a little plastic pan and covered in potting. When I pulled it out, I was really surprised that there was no thermal grease between the controller and the center of the motor. It was held in place by 3 M3 screws. Once the screws were out, the controller fell right out. No wonder these controllers burn out.





The stator came out of the shell very easily. I was really surprised that both shaft bearings are crunchy. This motor has maybe 5 miles on it. Why the bearings are this bad off is a real surprise! The stator is dipped in something...not lacquer. Lacquer isn't really a very good glue, but these windings are really hard to get apart. I wanted to unwind the stator, but the wires are bonded together so well that I can't unwind it. I have to cut the wire off instead. I've kept all the loops on 2 of the teeth and there are 64 loops so that means at 2 strands that there is 32 turns per tooth.





Took a while, but finally got the stator cleared off.

I've clipped off all these loops from each stator tooth. I've counted the loops from 4 stator teeth now and consistently get 64 loops or 32 turns. They average about 5" long. The motor had 32 turns per tooth with 2 20 awg stands. With 6 teeth per phase that's 960" or 80 feet per phase. That seems awfully long! Admittedly, I've rewound outrunners at much higher Kv's...like 50-80, not a motor with a kv more like 8-10.

Thanks for posting the info. That does seem like a lot of turns and would help explain why I can only get it to pull about 55A at 52v max. You might want to use fewer turns unless you plan much higher voltage.