Motor upgrade help Yukon Trail Inc. SM24

[danielkr]

Hello,

I need a motor upgrade for the subject e- bike. I'm trying to get to at least 750W. The bike has 175mm dropout, the hub has a drum brake on the left side and a single freewheel? (its a one sprocket that spins free when not being driven by the chain? not sure if thats the right word) on the right. It is a 24v 250W geared motor. I'd like to stay with the geared motor type for no particular reason but I often pull a small trailer. I've been hunting around and almost clicked the button to commit to purchase many many times and stopped myself unsure if I'd be able to attach the drum brake and single gear to the new motor. Does anyone know of a motor I could source that would allow me to do this?

The web site for the e-bike mfg. is yukontrailinc.com (audio warning they've splashed a picture and the audio of Alice Deejay's "better off alone" at the top level) and the bike looks like a chinese electric bike, long battery pack sits behind the seat post tube? (the tube that the seat post goes into?) Except now the battery box has a 48V 1000W controller in it and the batteries are going to be in the trailer.

Thanks,

Daniel

 

[Chalo]

That's a band brake most likely, not a traditional drum. It mounts on a normal freewheel thread. That's the good news.

The bad news is that you're not going to find a 170-something mm hub motor that has a band brake thread along with the amount of power you're talking about. Basically, for that spacing you have a choice between another motor like the one you have, or a much more powerful motor designed for fatbikes with disc brakes.

But a band brake plus a cheap low quality linear-pull brake like what you have aren't going to be safe and sufficient for an over-750W bike even before you hitch a trailer to it. I've worked on bikes similar to yours. They go 15mph and they're designed and equipped for 15mph, not more. If you want to go much faster, start with a better bike.

 

[amberwolf]

You could just add another motor, on the front wheel, and go 2WD. It doesn't have to be much, even 300-400w plus the rear existing motor would possibly do as much actual work, together, as a single 750w would. A 500w geared hub would do it, plus the rear 250.

I'd use dual torque-arms on the front fork though.


I've found that two motors together work harder especially at startup from a stop than a single motor does, for about the same loading on the battery. Plus there's redundancy.


i'd still improve the brakes, though, with better rim brakes on the front, at least. (a brake booster arch will also help) You could also add brakes to the trailer (I need to do that with mine; the last almost-600lb load I carried made it tough to stop quickly. :lol: ops;


If you used a DD motor instead of geared, you could use regen on the front motor to increase braking power. But you'd probably get more benefit from the freewheeling of the geared motor than you would from the braking power, and it's easy enough to get and setup good rim brakes on there.

 

[Chalo]

You could just add another motor, on the front wheel, and go 2WD.

That's a very good idea that circumvents all the spacing and compatibility issues in the rear motor.

For best results, the front motor's free speed should be the same or a little higher than the rear motor's.

The battery on that bike may not be rated to carry the load of two motors, or one much more powerful motor than originally equipped. If you exceed the max discharge of the BMS, the battery will turn off momentarily and cut all power to the bike. For this reason, it may be necessary to get another battery of similar capacity to power the second motor.

 

[danielkr]

When I first got this bike, second-hand, first thing I did was take the batteries out and use the space for a 48V 1000W controller; then, I got two wire baskets and hung them like saddlebags off the rear rack with a pair of 12V 17Ah SLA batteries in each one, and cruised around for about two weeks at about 30MPH. That was fun until one day the motor stopped working on my way back from Wal-Mart. I tested the setup later with a 16" scooter motor so I know the motor is toast.

I know I was pushing the motor way beyond its limits. And, I was putting way too much weight on that frame. My 170 lbs, plus the 120 lbs SLA bouncing around in those wire baskets on every bump (I had a 5th 12V SLA for powering lights), was definitely scary, unsafe, and lots of fun, for a time. I even rolled the back tire once speeding around a corner, lol. I'll never forget the day I flew past the guy pedaling and crossed the tracks just before the gates came down for the 15 minute long freight train.

So the second motor isn't really going to work for me in this case, I'm really needing to replace the first. I too have thought given the dropout width that fat bike motor and rim would be the way to proceed, and I've come close to hitting the buy button a few times, but as I said I'm so unsure I'm going to something that will work, that I can put the one single gear on. I'm also willing to switch to disc brake and fat, I have measured out and know the fat tire will fit the frame. And, having the batteries in the trailer will reduce the strain on the frame. The frame will be supporting just the rider, since the trailer hitches to the hub and the weight of the batteries will be centered on the trailer's hub points. Just four SLA's now, I've got a 48v to 12v transformer wired in to handle accessory power.

Could you please link something(s) from e-bay or amazon with that in mind? Rim, motor, spokes, disc; or, all-in-one, if it exists; 24" wheel; either with the single speed gear already on it, or that I can transfer it to; I would want mechanical caliper on the disc. I've already got two torque arms to attach.

I've already tried calling around, and the answer I always get back is "we sell what we sell we're not going to be able to help you find something to fit that." Also, no matter how many pictures I look at, they just don't give me 100% confidence. So believe me when I say I'm grateful for your expertise,

Daniel

 

[danielkr]

amberwolf, thanks for the brake ideas, I especially like the idea of fitting brakes to the trailer! I hadn't thought of that before, and with so much mass trying to keep the bike moving when I try to stop, it makes a lot of sense.

 

[Chalo]

Lithium batteries. Like, really.

If you gotta go cheap as hell, and you gotta go with SLA chargers, there's this:

http://m.ebay.com/itm/351864366128

SLA is not for vehicles anymore. Trust me-- I was one of the holdouts. But no. Don't carry that crap. It's not even cheap by today's standards.

 

[danielkr]

I know, I shake my head every time I look at them. But those Tenergy cells, Wow, affordable!!! At that price, I'm probably only two weeks away from starting to build a lithium pack. A few hours of overtime is all it would take...
THANKS I say that is spirit lifting, as tonight I've been testing old DeWalt battery packs trying to find NiCad cells to salvage sooo tedious, and still depressing knowing they're only 1500mah each cell. I think I'll just stop now, lol.

The SLAs came to me free and brand new; but yeah, damn heavy. They destroyed the kickstand that came with the bike. I did spend on a halfway decent charger for them -
https://www.batteriesplus.com/charger/car-and-truck/duracell-ultra/slc10005 which can be used for lithium also, 24V at a time... the packs came with Anderson connectors, so I attached two Anderson connectors to the controller, in such a way as to get 48V to the bike when plugged in, and when I needed to charge I disconnected the batteries from the controller and plugged the Anderson connectors of the packs to each other making for one big 24V pack so I could charge them together overnight.

 

[d8veh]

I've not tried it, but the Bafang 750w fat bike hub-motor should work as it has a drop-out width of aound 170mm and a spacing on the side where the band brake was. The only problem is that it's for a disc brake. I think Luna have them as a kit.

You can get disc brake adapter plates to hold the caliper, but I don't know how good they are.

https://www.alibaba.com/product-detail/48V-750W-Geared-Motor-Fat-Electric_60600493157.html

http://www.ebay.ca/itm/Bike-Disc-Brake-Bracket-Frame-Adaptor-for-160mm-Rotor-Bicycle-Mounting-Holder-US-/111746832211?hash=item1a04a15753:g:TVwAAOSwcgNZDUDv

 

[dogman dan]

uh,, IMO that frame is worth so little, its time for a complete do over.

Or, if its steel, modify it. Like bend in the frame enough to fit a typical rear hub motor. Or weld larger changes into it. Good bike to convert to a long tail cargo bike if it is steel.

There are a few things about the frame that are nice to have, like the sturdy welded on rack. But on the other hand, if there is anything you'd rather have in a bike, this is the time to go get it. Particularly, think about how the bike fits your body. if its perfect, sweet! if its not, then this is your chance to fix that. Maybe you'd be happier in the long run, to get a nice bike like an electra townie, or whatever fits your body real good and is a joy to ride.

 

[danielkr]

I thought I had started with a good foundation. I saw value in the frame because it had been designed for the purpose of being an electric vehicle. That sturdy rack really stood out for me as well; the extra pipe at the bottom; it is all steel, and that bottom tubing is fat. When I measured the dropout width I was like "Yes!" knowing I could put a sturdy moped wheel in it if I wanted to, and the hole in the tubing for running wires out-of-sight means that it wasn't going to look like one of my Frankenstein ideas when I was done messing with it. When I imagine where all the stress would be, including where the force is applied during drive and what is backing it up, it seems to be accounted for.

But now that I've had my fun with it, and since reading Chalo's post as well, I'm concerned about the safety of it long-term. I can't discount the fact that no matter what it looks like to me it was designed in China and manufactured in China for the purpose of going 15-17 MPH and probably won't handle much beyond that, because the Chinese are quite efficient at meeting specifications.

As far as fit and feel, I can't deny that I felt dangerously high off the ground when moving over 25 MPH. I have given serious thought to frame modifications that would put me closer to the ground, lowering my center of gravity, even if it meant losing the pedals altogether. Lengthening the frame, perhaps putting 20" fat wheel on the rear instead of 24", cutting the head tube off and reattaching it 30 degrees different; I just bought a Razor MX650 from wal-mart and feel safer on it than I ever did on this.

Maybe it is time to cut the cord and hang this one on the shop wall. I have learned a ton of things about motors, controllers, troubleshooting, etc. in the time I've had it. I've taken apart and reassembled the motor so many times I could do it in my sleep, trying to find the power leak. The new knowledge and hands-on experience is worth many times more than the $350 I have invested in the whole thing.

I just bought that set of batteries pointed out in Chalo's post and a cheap e-bay kit to convert my mountain bike, I'm going to commute with that until I have a solid plan for something I can truly appreciate and enjoy.

I'm truly glad I stopped and asked for input and opinions. I simply never asked myself if I'd really be happy with it in the end until now.

Thank you,

Daniel

 

[amberwolf]

If you really want something lower that could handle the higher speeds, and are comfortable with building/modifying frames, you should look into my CrazyBike2 thread.


I only ride it at 20MPH, because that's the limit here in AZ, but it gets there in around 4 seconds. I know it can do 25-30MPH with what's on there now, probably more, though stopping from those speeds woud need better brakes, probably better tires (moped or motorcycle types).

If I had the controllers/motors on there setup for it, and brakes were replaced with something that could stop it from those speeds, it could safely handle 30-40MPH (it's done over 30 on a kart track race in a previous configuration that wasn't nearly as good as it is now).

 

[dogman dan]

Well, if its steel, time to get a cheap wire feed welder and start experimenting with it. Once you get a bit of practice with the welder, start modifying that frame.

Move seat lower and to the rear, and add disc brake mounts to start with. Maybe later, even modify it to that small moped rear tire.

But for now,, maybe a steel 7 speed beach cruiser would be a good choice to put your new kit on. There are models with the welded on rear rack.

Or,, make your own, as a first welding project.

Turn that bike into something like this. It started as a Schwinn one speed, now its a longer ( more stable at speed) 7 speed with dual disc brakes.

Eventually, you could work up to this.