Mad Max Schwinn Chopper, should I?

Rousabout

100 µW
Joined
Oct 13, 2020
Messages
8
I've been wanting to build an ebike for sometime, but lacked the inspiration. Then I came across this in a junk pile.
20220524_133105a.jpg

As you can see, it's clearly been neglected. But otherwise all the major parts look to be straight and true. In the short term I want to get this bike going safely as cheap as possible and embrace the Mad Max look.

It's not home yet, but from a quick once over, I think mechanically all it needs is a few spokes, new tires, tubes, brakes, a chain and a full overhaul of its bearings.

The 120mm bottom bracket and fat rear aren't regular standards where I live in Australia. So if I take this project on I'll need some guidance from our North American friends who have more experience on these things before I start ordering parts online.

I don't know if tires are available for this bike. As I understood it, I was told at the bike shop the rims on these Schwinn choppers aren't standard and wont accept regular 20" fat bike tires. Am I better off ordering new wheels with 175mm axles or was the guy at the shop misinformed?

Is there anything I should know about the 120mm bottom bracket? will I be able to drop standard cups and bearings in? will it be possible to drop in a new sealed bottom bracket later? I haven't worked with these old style bearings for over 30 years, are they easy to order?

I'm nomadic, but where I live now, Darwin, Australia. It's all flat and the weather is perennially hot and swings between dry or brutally humid and monsoonal.

My Goal in the short term is to get the bike going and powered as cheaply as possible with a view to upgrade and if I don't like riding the chopper, be able to adapt the electricals to another bike. In the longer term I'd like to move the motor from hub (if I take that route) to mid frame, add an internal geared hub and a torque sensor.

The cheapest kit I can find is available in Australia mail order. A 26" 1000w Voilamart AU$260 front or rear, that could be dropped into the forks or have the rear re-laced with the 20" rim (with a customized 175mm adapter?) . As far as I can tell, other options are twice the price and need to be sourced from abroad.

I would really appreciate any help from the community and I'll endeavor to keep you posted on my progress.
 
Take the wheels off and measure the dropout width for the rear if you want a rear hub motor.
 
A geared rear hub motor makes sense for that bike. You should get an unlaced hub and lace across the rim to the opposite side, otherwise you'll end up with a wheel that has no effective bracing angle.

Look for a drum or roller brake front wheel.
 
Calab I don't know what I want yet, I'm seeking advice. I took these measurements when I saw the bike.
IMG_20220602_182129.jpg

Thanks Chalo, Why do you recommend the geared hub and drum or roller brake for the front wheel? There are plenty of gearless hubs advertised online already laced. I laced a new hub into a bmx wheel when I was a kid, but that was a simple case of copying the pattern from the old hub. I'll have to look at a picture of another wheel online...

There is a lot of space in the rear triangle, I thought it might be a good place for a mid mounted motor. What are your thoughts? I was thinking of using a hub motor from a bike or scooter because they have such low Kv ratings with good torque without excessive gearing requirements. What are your ideas on this?
 
G'day Roundabout.
Go for it mate. I'm down south near Melbourne & knocked together a chopper out of the same bike,,
chopper.jpg
You'right about the rear triangle. I mounted a small hub motor there for a mid drive setup. Lots of room.
Had to replace the rear V brake with a disc brake.
One thing to watch is the seat post. I weigh around 81kg & the post tended to bend until I added a sissy bar to help support it.

AussieRider
 
Well, you said 'Mad Max' and that got my interest. Can't wait to see how this comes out!

Here is an image search for inspiration:

https://duckduckgo.com/?t=ffab&q=mad+max+motorcycle&ia=images&atb=v149-1&iax=images
 
Rousabout said:
Why do you recommend the geared hub and drum or roller brake for the front wheel?

Drum or roller brakes don't require brake mounting points, which your bike doesn't have in front.

A fat geared motor will have wider flange spacing, maybe enough that you don't have to lace spokes to the opposite side of the rim. Also it will pull harder watt-for-watt at low speed than a direct drive motor, and allow you to coast better without motor drag.
 
Looks like a good project.

The bottom bracket is English type, so, regular cups and bearings fits. The spindle is getting hard to find. Amazon have 120mm BB sealed unit. You can get by just clean up the spindle because you can't pedal much to catch up the speed of the motor, unless you replace the rear free wheel to 6-7 sp. But that's another can of worms.

Regular size rear motor won't fit, because rear drop out is about 2" wider than ordinary bikes. The axles are too short. You have to get a motor for fat bikes. If you want to put a front motor, most of motor fits.

It looks like, you don't have front brake. Some Stingray comes with V brake pins, some don't. If that the case, you may want to put the pins. I took the foot rests out and used the bolt holes to put a bracket and pins.

Looking forward to see the progress.
 
AussieRider said:
G'day Roundabout.
I mounted a small hub motor there for a mid drive setup. Lots of room.
Had to replace the rear V brake with a disc brake.
One thing to watch is the seat post. I weigh around 81kg & the post tended to bend until I added a sissy bar to help support it.

AussieRider
Not a bad effort for something 'knocked together'! There's no way I could out do your work, so I think I'll def have to embrace the Mad Max in me! Your disk brake caught my eye and I had concerns about the seat pole. I'm not a fan of sissy bars, but I don't have a better solution...
I have a few questions for you. Did you have a problem finding the rear tyre? I've been told this rim has a different diameter to the other 20" fat bikes out there we see now. It looks like you have 2 free wheel hubs on the motor, how did you do that? And did you do anything to stop the free wheel from winding itself off the hub? Your battery box like the rest of the bike looks professional did you custom build it? Most importantly, how is it to ride? Is it comfortable on longer rides? I can spend a full day riding and it's as important that I'm comfortable as I am proud of what I ride!

Every detail in your work complements and improves on the original design well done mate!

Thanks for the inspiration.


Ishikawa said:
, Thanks, all very helpful! There are mountings for v brakes from a doner bike. Down the road I think I'll look at disc brakes, internal geared hubs if I find this is something I enjoy riding.

Chalo said:
A geared rear hub motor makes sense for that bike. You should get an unlaced hub and lace...
It looks like I won't have a lot of choice. All I can find for sale in Australia for 170mm is an all in one kit laced to a 26" hoop and a piddly 36v 13ah battery...

4πr^2 said:
Here is an image search for inspiration:
Thanks mate! I feel more inspired
 
I second going bigass rear hub motors, mostly because I think the "filled wheel" would benefit the look and let you cruise like a custom chopper when you want (I think that's also why Chalo advocated for the geared hub, low speed torque). I absolutely LOVE the Mad Max aesthetics, just remember that everything in that series has a place and purpose- I suggest, going to local wreckers and taking a peek at whats there, and letting art and inspiration guide you.

Because your weather is pretty brutal with wild moisture swings, I'd honestly recommend potting of whatever battery you choose or build. Hummina Shadeeba here has done so and gave me points, and discussions with LFP at his job at a lithium battery recycler implies that most batteries die due to corrosion and condensation buildup within the pack. Hopefully, I'll be joining you soon on the Mad Max bike look!
 
G'day mate.
Thanks for the kind words.
AFAIK, the rear tyre is standard 20" fat bike ( maybe Chalo can clear that up ).
I have only 1 freewheel on the motor
midchop1.jpg
The inner sprocket that goes to the rear wheel is a fixy thinned down a bit so there's enough thread for the outer freewheel that goes to the pedals. The freewheel acts as a locknut to stop motor torque unwinding the fixy.
I built it all myself. The battery box top cover is a heat sink reshaped a bit. Motor mounts were cut with a jigsaw & hand folded.
When I first added the sissy bar I used a banana seat that was slim, firm & hardly any padding, unlike my 63 year old arse. After 10 minutes riding I'd feel violated so I made some mounting brackets & fitted the Stingray seat.Nice, fat. & soft like my bum.
I agree with Chalo about the front brake. A roller brake is a neat solution though they're not always that powerful.
Not that it matters since the back brake does most of the work on a bike with this much rear weight bias.
Hell, in the classic movie Easy Rider Peter Fonda's chopper didn't even have a front brake!
Not that I'd ride it, a shovel head with foot clutch & hand gearshift?

AussieRider
 
CONSIDERABLE SHOUTING said:
I'd honestly recommend potting ... Hopefully, I'll be joining you soon on the Mad Max bike look!
haha I'm glad a few people are with me on the mad max theme. I honestly thought I'd be on my own there. The bike will evolve slowly. I've so many ideas for it and some will have to wait. Right now my focus is getting the it in a condition I'm happy and comfortable to ride. This town has few wreckers, it's like the wild west, availability is poor and nothing is cheap let alone free. :shock:

Feeling stupid I had to google "battery potting" haha Great idea! Are there any cheap and easy way of potting batteries without insulating them? I don't think keeping them above min operating temperatures is my biggest concern. :flame: :flame: :flame:

Is there any way I can protect/water proof the motor? I'm afraid IP56 will have ingress from humidity alone.

I'm still undecided which way to go with the motor. Everything requires me to re-lace the hub, so I was thinking I could skip this step and mid mount it. I'm tempted to be completely impractical and fill the frame with an obnoxious direct drive hub and down gear it to match pedaling cadence for more torque. I've narrowed the choice down to the 1000w direct drive hub kit or the smaller geared hub. Link below.

https://www.ebay.com.au/itm/165202876433?hash=item2676dbd811:g:74kAAOSwJGthoGRr

AussieRider said:
G'day mate.
Thanks for the kind words.
AFAIK, the rear tyre is standard 20" fat bike ( maybe Chalo can clear that up ).

The inner sprocket that goes to the rear wheel is a fixy thinned down a bit...

AussieRider
Genius! I'm pretty sure I'll do that. Cheers!
As much as I love your battery, I don't think I'll be able to emulate it. Reality is pushing me towards something conveniently removable. I'll probably drop the motor in that space.
 
Rousabout said:
Feeling stupid I had to google "battery potting" haha Great idea! Are there any cheap and easy way of potting batteries without insulating them? I don't think keeping them above min operating temperatures is my biggest concern. :flame: :flame: :flame:

Shadeeba recommended to me going 60D for hardness, and used a water-clear poly from this site. I think they used this one:
https://bjbmaterials.com/polyurethanes/castable/rigid/non-fire-rated/tc-861-rev1-a-b/
I also found this site looking for details as well- that HTCPX really interests me, because then the pot also acts as a massive heat sink- potentially, it could spread the heat out and could be combined with copper/nickel sandwiching for connections for great heat control.
https://www.electronicsweekly.com/news/products/emech-enclosures/thermal-potting-compounds-batteries-2020-08/

Is there any way I can protect/water proof the motor? I'm afraid IP56 will have ingress from humidity alone.
There's a coating people have used here on their high-power builds that's red in color, I know someone mentioned it in the leafbike motor thread in the last couple of pages (~86).
 
Hi people's.
Mate, I gotta fess up. That battery box is just MDF tarted up with some carbon fibre look vinyl film that the street wankers wrap the fake aero bits on their rice burners in. Respect to the fair dinkum JDM tuners, but a Kia Rio with a 6" tip on the standard exhaust, vinyl wrapped plywood wing & rattle can painted wheels ( with matching overspray on the tyres ) just gives me a soft on.
Rousabout, since you're going with a Mad Max look, I don't think you need worry about chasing down the tyres like mine. On your project there's only 1 way to go. Knobbies. Ice spike tyres would reply look the part but on paved road would be like riding a vibrator.

AussieRider
 
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