A2B build

[ElectricGod]

I have 2 of these motors. I'm thinking one will get wound for more copper, but the same kv.

Now that I have one apart all the way, I can see how this motor could be rebuilt into a proper outrunner driven from the shaft. I'll see about rewinding it for more like 50kv. It will take some machining and a couple of custom parts to make it spin on a shaft, but this motor will probably make for a really good pancake style outrunner. I'm thinking I'll be able to get something like 10-15kw out of it.

 

[ElectricGod]

The hub rewind is coming along nicely. It's going on a friends A2B so I'm teaching him how to rewind a motor in the process. I thought I was slooow...he's even slower. Once I have pics of the rewind...I'll post them.

I've been tempted several times to pull strands for the phases and figure out what is the maximum amount that will fit. Nope...he needs to do it all.

 

[ElectricGod]

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.

Factory runs 10S or 36v. We are going to 66v so I don't want to bump the Kv at all. 32 turns per tooth will probably not change.

 

[fechter]

Factory runs 10S or 36v. We are going to 66v so I don't want to bump the Kv at all. 32 turns per tooth will probably not change.

That should be good. With some field weakening, it should go faster than you want to go on that frame.

 

[ElectricGod]

Factory runs 10S or 36v. We are going to 66v so I don't want to bump the Kv at all. 32 turns per tooth will probably not change.

That should be good. With some field weakening, it should go faster than you want to go on that frame.

I picked up 2 A2B's at the same time. My freind Dave will get the rewound hub back in the wheel. Mine will get reworked into an outrunner and rewound for more like 80kv and mounted as a mid-drive. With more like 8 turns per tooth, whatever Kv that is, there will be loads of room for more copper per turn. The motor ought to become more like 8 kw or more. So on Daves A2B, he'll probably see 40mph tops and acceleration will be moderately good like 0-30 in 30 seconds. He will get a PowerVelocity 12 fet controller...more than enough for his motor. Mine...who knows...lots more wattage, speed and acceleration and probably 18 fet. I'm betting 60mph+ top speed.

 

[fechter]

You'll probably want to upgrade the tires on those. The stock tires have terrible handling and go flat easily.
I put moped tires on mine. There are some good choices out there.

 

[ElectricGod]

You'll probably want to upgrade the tires on those. The stock tires have terrible handling and go flat easily.
I put moped tires on mine. There are some good choices out there.

For mine...absolutely. For his, I bet he wears them out before replacing them.
I'll probably give him mine. I did notice they were not great.

 

[fechter]

The stock tires are downright dangerous in tight corners. The sharp edge on the tread washes out if you lean over enough to get on it. A round profile tire is a huge improvement.

 

[ElectricGod]

The stock tires are downright dangerous in tight corners. The sharp edge on the tread washes out if you lean over enough to get on it. A round profile tire is a huge improvement.

I had weak tires on my Currie scooter at first, they were like you describe...more dangerous than anything. Good shoes on your wheels is always the best option!

 

[ecross]

Hello EG,

thanks for the A2B infos. Is the rear good for a QS 205 Motor?

BR
ecross

 

[ElectricGod]

Hello EG,

thanks for the A2B infos. Is the rear good for a QS 205 Motor?

BR
ecross

Sure, you can unstring the factory hub and replace it with a 205. Get a 36 hole version. The 205 is somewhat larger diameter so you'll need shorter spokes.

 

[Amiran]

A2B Metro dropout plates for metal cutting.
This worked for me after i snapped ears off the original one.

 

[ElectricGod]

A2B Metro dropout plates for metal cutting.
This worked for me after i snapped ears off the original one.

yes...thanks...i was already skeptical the factory dropouts were more than suggestions. I'm thinking of making an add-on set that extend the swing arm another 3-4". That will give me some space in front of the wheel to mount an outrunner.

 

[Amiran]

Then watch for cracks if they start to appear ear the welds of tubelar and cast alloy sections of swing -arm. You never know.

 

[ElectricGod]

Then watch for cracks if they start to appear ear the welds of tubelar and cast alloy sections of swing -arm. You never know.

I'm going to assume they will break and just reinforce them before they ever get the chance. Most people with A2B's that run more than the factory motor invariable have to reinforce the drop-outs. Might as well just assume it's going to happen...

 

[ElectricGod]

I've been helping my friend rewind his A2B hub. He's not ever done anything like this and he's really slow. Last night I got him a single phase worth of wire and in an hours time he got one tooth wound and then miscounted the number of turns several times. LOL.

Well...at least the entire stator is marked up so if he follows that, he at worst will miscount the turns per tooth. I sent him home with the wire and the stator. Hopefully he will get that one phase done.

My hub will get rewound for like 80kv...when I have time for it. I have 2 other motors to rewind first.

 

[ElectricGod]

Edit:
I found the cross section area for 28 awg (.081 mm squared) and 20 awg (.5176 mm squared)
10 x .081 = .81
14 x .081 = 1.13
16 x .081 = 1.3
2 x .5176 = 1.035

That was a waste of time at 10 strands. 14 strands would have gotten him 1.13 mm squared. I probably could have gotten 16 strands to fit.
Fooey! I knew I should have insisted he pull it all back off and do another 4 strands. All that rework for nothing. I should have checked the cross sectional area before I let him wind it with 10 strands. The total diameter of 10 strands of 28 awg with insulation is more than 2 strands of 20 awg with insulation.

Well that took him forever...
He gets a phase done every time he visits...so finally all 3 phases are rewound. Hopefully they are all correct too! I tried to convince him to add another 4 strands for a bit more fill back when he was half way through the first phase. That would have meant unwinding it again and he was unwilling after having just counted to 32 3 times without messing up This is 10 strands at 32 turns of 28 awg. There's more room here that could have been filled. I would have gotten a good bit more on the stator. Ah well...it's his first attempt at anything like this. I coached him and he did all the winding.

The original wind.

New wind close-up:

Old wind close-up:

 

[kdog]

Hate you add more bad news to your build EG, but I built up that exact frame and can add a few more draw backs.
The front forks are shit... They look nice with a low friction coating but are dirt cheap inside with only a spring and no dampening. They are also manufactured with not enough rake so they are very twitchy and unsteady at high speed. Anything over about 60kph is unsettling although it only gets mildly worse as the speed increases. I've had mine up to 90pkh and it's pretty bad but tolerable for short periods. And, if you want to replace it you'll need to order a fork with an extra long steerer tube cause of the custom frame.
The rear swing arm is a pos all round but I think that's been covered. Lots of photos of that broken weld if you google it (what were they thinking putting a weld there )
Watch out for razor sharp edges inside the frame.

I've done several thousand Kms on mine and it's been OK... Not great but not the worst. Kinda stuck with it now cause it was an expensive build. (adaptto midi-e, 3000w motor and big battery)

 

[ElectricGod]

Hate you add more bad news to your build EG, but I built up that exact frame and can add a few more draw backs.
The front forks are shit... They look nice with a low friction coating but are dirt cheap inside with only a spring and no dampening. They are also manufactured with not enough rake so they are very twitchy and unsteady at high speed. Anything over about 60kph is unsettling although it only gets mildly worse as the speed increases. I've had mine up to 90pkh and it's pretty bad but tolerable for short periods. And, if you want to replace it you'll need to order a fork with an extra long steerer tube cause of the custom frame.
The rear swing arm is a pos all round but I think that's been covered. Lots of photos of that broken weld if you google it (what were they thinking putting a weld there )
Watch out for razor sharp edges inside the frame.

I've done several thousand Kms on mine and it's been OK... Not great but not the worst. Kinda stuck with it now cause it was an expensive build. (adaptto midi-e, 3000w motor and big battery)

This hub motor is for a friends low power build. I'm not worried about his A2B being mostly stock. He has very low expectations and would have been happy with the bike working as is from the factory. It's me pushing him to go for more performance.

Mine wont be using the factory hub motor or any hub motor. I have a Revolt RV-100-Pro outrunner that I will be mounting to the underside of the swing arms right in front of the tire. I'll run 219 chain to the back wheel. I'm planning on 82v and that will get me 50-55 mph on level ground.

In this set up with a much lighter back wheel and the motor weight at the pivot, the stresses at that bend in the swing arms is greatly reduced since there won't be very much unsprung weight past those welds. Regardless, I'll add steel to the joint to strengthen it. in the same piece of metal I'll extend to the rear dropouts to reinforce them as well.

Front forks...thanks for the input. I already knew they were just springs, but I didn't know about the rake issue. LOL...this bike was never intended to be powerful or fast...no surprises it has issues at greater speeds and power. AND...of course...I have every intention of making my top speed right where you say they get twitchy.

Inside the frame is of little concern to me. My pack will be far too large to fit inside anything. I plan to build it to fit around the square tubes and low as possible around the V shape between the seat tube and the main tube. I want its weight in the middle of the frame as much as possible. The controller will mount on the top of the swing arms above the motor. I might just make a single bracket that mounts the motor and controller together on the same bracket. That development will come later. I'm waaaaay early into my personal A2B build.

I have bought a track hub for the back wheel. They are fairly inexpensive. Mine cost $50. They have freewheel threads on both sides of the wheel hub for mounting sprockets and brake rotors. I have new spokes for restringing my back wheel for use with the track hub. I'm still waiting on 4mm ID washers to arrive so I can strengthen the rim holes for the spokes. Restringing the back wheel is easy. Here's most of the parts for the back wheel.

Somebody spent a lot of effort in making the A2B frame and making a good looking e-bike. It is all nicely fitting parts. Sometimes cheap parts, but it all has good fit and finish with no slop and rattling like Chinese crap has. It's a nice looking e-bike design. Some e-bike designs...it takes all my effort to not vomit when I look at them. All the welds are TIG...which is expensive and NOT easy to do. The entire frame is anodized as a single part or painted with decent grade paint. The A2B does have design oddities...like non-straight swing arms, weak rear drop-outs and spring shocks, but it also has a lot of good qualities too.

 

[ElectricGod]

It's time to get better tires...
1. They need to hold 5kw at the back wheel.
2. They need to handle a top speed of around 55mph.
3. Street riding will be 80% and dirt riding 20%.
4. I was thinking 1.95 to 2.4" wide.

What tires are you using?

I've done some research on tires and picked these out. Some are better for what I intend than others.

INNOVA: https://www.amazon.com/dp/B07H2P433V/ref=as_li_ss_tl?SubscriptionId=AKIAJO7E5OLQ67NVPFZA&ascsubtag=513862178-2-2091242132.1575421835&tag=shopperz_origin3-20&th=1

Kenda Kontact: https://www.amazon.com/KENDA-Kontact-Black-Bicycle-Tires-1/dp/B01AVOM5Z2/ref=sr_1_10?dchild=1&keywords=Kenda+Kontact+Tire+20%22&qid=1575536791&s=sporting-goods&sr=1-10

Goodyear folding bead: https://www.amazon.com/Goodyear-Folding-Bead-2-125-Black/dp/B019Q77GPE/ref=as_li_ss_tl?ie=UTF8&qid=1549565421&sr=8-4&keywords=bmx+tires&linkCode=ll1&tag=jon190e-20&linkId=e5c648f2e02e62b0eda73af13ad5a126&language=en_US

Sunday Street Sweeper: https://www.amazon.com/dp/B06Y3CHRPF/ref=twister_B01M3Y4W7Q?_encoding=UTF8&psc=1

Callaway Odyssey: https://www.amazon.com/Callaway-Odyssey-Tires-Slick-20X2-4/dp/B01MR7ZBKT/ref=sr_1_7?crid=Y2O59OAY8QOM&dchild=1&keywords=20+x+2.4+bmx+tires&qid=1575535712&sprefix=20+x+2.4+%2Csporting%2C179&sr=8-7

I got another track hub. The first one is 32 holes, not 36 holes. It arrived today. I put brass washers under the spoke nipples to help hold the 5kw of mid-drive power I'll be getting from the Revolt RV-100-Pro outrunner. Stringing up the back wheel was not hard and the rim runs nice and round.

The track hub has freewheel threads on both sides. The right side will get a 219 sprocket and a single bike sprocket on a freewheel so I can pedal. The left side will get a freewheel threaded brake rotor adapter.

 

[fechter]

I used 16" moped tires on mine. The 16" tires fit a 20" bicycle rim. Moped tires are much heavier and I trust them at high speeds much more than typical bicycle tires.

This place seemed to have the best selection:
https://www.treatland.tv/SearchResults.asp?Search=16"+tire

 

[ElectricGod]

I used 16" moped tires on mine. The 16" tires fit a 20" bicycle rim. Moped tires are much heavier and I trust them at high speeds much more than typical bicycle tires.

This place seemed to have the best selection:
https://www.treatland.tv/SearchResults.asp?Search=16"+tire

Moped rear tire 2.jpg

I have chain line limitations. I need a narrower tire and I want to stick with the 20" rims...especially so since I've already strung the back wheel for it.

I do agree that moped tires will be tougher.

My right side of the track hub will mount a 219 sprocket and a freewheel/bike sprocket side by side. That means the 219 chain will be pretty close to the side wall of the tire. I can't use a 3" tire. 2.14" is all the more tire width I have available to clear the 219 chain.

 

[ElectricGod]

I've purchased a set of Schwalbe Big Ben tires in 20x2.5. They are rated for higher speeds and higher loading than most tires. The tread pattern looks like it will work well for road or off-road use. It might even do well when it snows here so I can ride summer or winter. There are sooo many tire options and not much feedback on any of them beyond use for BMX. I won't be doing tricks on the A2B or jumping. I'll be doing 35-50 mph most of the time riding to and from work.

https://www.amazon.com/gp/product/B009O0CN8Y/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

I'll be going tubeless. I have 1" wide electrical tape, but I really want to use something that doesn't possibly turn to goo in a year. I ordered some 30mm wide PET tape to seal the spoke holes. The glue used lasts for many years, the tape is really tough and I can use PET tape for lots of things besides this. I ordered some Stans tubeless tire sealant as well. All the rest of my EV's are tubeless, this bike should be too.

2.5" wide tires will leave about 1/8" clearance for the 219 chain. This image is of my Currie stand-up scooter. It has about that much clearance and the chain never rubs the tire. 219 is very stiff side to side so there is very little movement in this direction. I think I'll be OK at this clearance.

 

[ElectricGod]

The Schwalbe tires arrived. I'm still waiting on proper tape for sealing up the rim so this is with the 3" tube inside.

It's light...and that's what I expected from a bike tire. Delete the tube and that will just get better. At 30 psi, I can not roll the tire over with my hands. The side wall stays stiff. At least from that perspective it will definitely out perform the factory Kenda tires. Grip...who knows. Tread depth is about 2mm. It will be fine on pavement, dirt or grass. Mud or snow...fairly useless. Whether this tire can hold 5kw...we'll see. I know moped tires are more resilient and a better option. Everything else I have ever built has moped tires, but they are heavy. I'm learning...never built an e-bike before. Decent power on bike tires...I expect the back tire will wear pretty quickly. I have seen converted bicycles with more power riding on bike tires. They do OK...so should I.

These Kenda tires are truly awful...lol...like we didn't already know that! With the Kenda at 40 psi (MAX pressure) and the Schwalbe at 30 psi (low pressure), the side wall movement on the Schwalbe tire is easily 1/3 that of the Kenda. At 55 psi, I can't hardly make the tire flex at all on the Schwalbe. Purely subjective at this point, but so far so good.

 

[fechter]

These Kenda tires are truly awful...lol...like we didn't already know that!

Boy, you can say that again! Those Schwalbes look like a great alternative for a stock A2B, which I still have a couple of. The really bad feature on the Kenda tires was that sharp edge on the side of the tread. If you lean into a corner hard enough to get on that edge, it just washes out and you crash. That and they get flats just by looking at them wrong.