Will this bike break if converted to ebike?

[Brett1010]

Hey I’ve got this weird/cool bike (pics) I found and fixed up and want to convert to an ebike for burning man (flat but bumpy terrain).

A guy who does a lot of ebike conversions told me the motor would pop out if I put a motorized front wheel.

Guys at my bike shop also told me the frame might break if subjected to bumps.

I’m willing to take some risks here if it’s a 50/50 chance it breaks. But if it’s a 90% chance I probably wouldn’t take it.

Does anyone have any opinions on this as far as the strength of the bike?

Pics attached.

Video here: NycBicycle.MOV

 

[Hummina Shadeeba]

Just do low power and surely be fine.

 

[Slowchris11]

Don't put a motor in the front. It will not like it at all. Middle and rear are OK if you take something cheap and weak.
Maybe you try to get it up to 20mph downhill and judge how safe you feel and how well the brakes work.
Better wear a helmet.

 

[marvin78]

No to front hub motors, afaik the straighter your steering tube angle the more issues with handling you will have. And old bikes are usually pretty straight.

I love the looks of the frame, I would love converting something like that! Not sure which mid drive would fir that frame due to the almost horizontal downtube coming off the bottom bracket.

Also, unless I'm sorely mistaken, that's a steel frame. Steel frames don't break ( .. don't correct me, lol ). Well not easily anyway. You can bend a steel frame back into shape a whole lot more as any alu one. Also makes it easier to weld / fabricate.

I would like to have a battery which would fit nicely into the bottom of the curve on the upper, preferably with the controller all nicely worked in that nice triple piece frame.

Anyway enough about that, wasn't the question. Strength wise, can't judge from photos as it depends on the state of those rusted parts -> superficial is not an issue.

Sand it down to bare metal to be sure, but I think it should be fine, and that thing will be a sick beach cruiser ( well in my mind, I'm looking forward to see what you'll do with it ).

edit: I would make this ofc 'street legal'. The faster you want it to go, the more rigidity you need in that frame.

That fork looks mighty interesting, I would restore it as a bike if not sure it could handle an ebike motor it looks like a gem.

edit2: Burning man is in the dessert right? Those skinny tires won't do well on the sand.

 

[richj8990]

No to front hub motors, afaik the straighter your steering tube angle the more issues with handling you will have. And old bikes are usually pretty straight.

I love the looks of the frame, I would love converting something like that! Not sure which mid drive would fir that frame due to the almost horizontal downtube coming off the bottom bracket.

Also, unless I'm sorely mistaken, that's a steel frame. Steel frames don't break ( .. don't correct me, lol ). Well not easily anyway. You can bend a steel frame back into shape a whole lot more as any alu one. Also makes it easier to weld / fabricate.

I would like to have a battery which would fit nicely into the bottom of the curve on the upper, preferably with the controller all nicely worked in that nice triple piece frame.

Anyway enough about that, wasn't the question. Strength wise, can't judge from photos as it depends on the state of those rusted parts -> superficial is not an issue.

Sand it down to bare metal to be sure, but I think it should be fine, and that thing will be a sick beach cruiser ( well in my mind, I'm looking forward to see what you'll do with it ).

edit: I would make this ofc 'street legal'. The faster you want it to go, the more rigidity you need in that frame.

That fork looks mighty interesting, I would restore it as a bike if not sure it could handle an ebike motor it looks like a gem.

edit2: Burning man is in the dessert right? Those skinny tires won't do well on the sand.

Steel frames don't break. Look at that frame. Is it even from the 20th century? Is that fake rust or real rust on it? And he has rim brakes on the bike. A bike that probably doesn't ride very well even on pavement the way it is, and he's going to add 20-30 lbs to it and electrify it. Sorry to be overly cautious like his friend but I agree that this is an emphatic no on the conversion.

 

[Hummina Shadeeba]

The front suspension won’t take a powerful front hub but an old steel frame is strong and surely a rear hub would be fine. It depends how much torque and how well the hub is held in the dropouts

 

[marvin78]

Steel frames don't break. Look at that frame. Is it even from the 20th century? Is that fake rust or real rust on it? And he has rim brakes on the bike. A bike that probably doesn't ride very well even on pavement the way it is, and he's going to add 20-30 lbs to it and electrify it. Sorry to be overly cautious like his friend but I agree that this is an emphatic no on the conversion.

He should strip that frame down before we can be sure how deep the rot has gotten.

As I see this, it's piece of art. Like I said, I would love to see this fully restored even as a normal bike. If you build it to cruise along on festival grounds where you're not supposed to go quick anyway, I don't even see rim brakes as a serious issue. Remember road bikes have been using rim brakes for a long time, it just needs a rider to know their limits. Even on a bike path this would be more then fine.

Wouldn't take it in mixed traffic though, and since I am reminded that US infrastructure basically has no real interconnected cycling only infrastructure this would limit it's practical use over there.

I'd say the frame / bike itself is a gem waiting to be restored, and that the frame should surely be able to handle a low power rear hub motor. In my mind I would build it as stealthy as possible, keeping the motor size down as much as possible. Afaik those camp sites are flat as a pancake ( dessert ) so you don't need that much anyway.

But again, need to check that rust first. I hope he lives in an arid environment and that rust can be wiped off with some sandpaper.

edit: also, since you did mention it without outright correcting me -> steel frames bend or crack, compared with alu frames which can just snap almost as violently as carbon frames. Plenty of people swear with the chromoly steel frames for a reason even if you do need to take care they don't rust.

 

[Chalo]

That's a lowrider bike. It's not optimized for riding, but for parking in a visible location.

It's a safe bet that the frame tubing is thick enough that no normal amount of rust could compromise it structurally. That's not a concern.

The head angle is ordinary. It's the amount of fork offset that's out of the ordinary. However, that on its own is not a problem for front hub motor use. In fact, the "reverse caster" effect from excess fork offset may be somewhat tamed by the motor pulling the fork into its forward orientation.

The real problem with that fork is that it's a high pivot springer. It doesn't have actual fork dropouts, only tubing that's squashed flat and slotted for the axle. It won't withstand axle torque from the motor, and it doesn't provide good structurally sound places to anchor a torque arm.

There's another problem with a high pivot springer fork that is unrelated to e-bike conversion, but exaggerated by a front hub motor. The direction of suspension travel is at more or less a right angle to the desired direction. So its suspension action is more or less worthless to improve ride quality or traction, even if it moves around a lot while riding. But it will articulate from motor propulsion force or motor braking force, inchworming the bike's wheelbase without helping its ride.

There's no practical reason the bike can't be electrified with a hub motor, front or rear, but the technical details would be much easier to resolve with a rear hub motor. Also the bike isn't intended for-- or any good at-- fast riding, so a low (ish) speed electric drive would be much preferable to a high speed one. A system that maxed out at 20 mph would be as fast as I'd ever consider for a lowrider bike, and even that speed might be pretty hairy.

 

[marvin78]

That's a lowrider bike. It's not optimized for riding, but for parking in a visible location.

It's a beauty isn't it. I'm actually a bit jealous we don't have a lot of these style frames around here

It's a safe bet that the frame tubing is thick enough that no normal amount of rust could compromise it structurally. That's not a concern.

The head angle is ordinary. It's the amount of fork offset that's out of the ordinary. However, that on its own is not a problem for front hub motor use. In fact, the "reverse caster" effect from excess fork offset may be somewhat tamed by the motor pulling the fork into its forward orientation.

Thanks for the correction. I seen rust eat through thicker steel but it depends on the steel, how long it's been exposed and the humidity. I to think it's superficial, but tbh not sanding it down to bare metal and giving it a proper paintjob ( even with a spray can... ) should be a crime. Especially paying attention to the welds / connections and dropouts. Just to be sure.

Strange to realize I pictured this steering setup to feel less stable under load not more, I thought the motor would instead make it more twitchy.

The real problem with that fork is that it's a high pivot springer. It doesn't have actual fork dropouts, only tubing that's squashed flat and slotted for the axle. It won't withstand axle torque from the motor, and it doesn't provide good structurally sound places to anchor a torque arm.

On the close up, the pinched part isn't that long and you should be able to attach a longer torque arm. Considering how this is definitely not meant to be fast, I was more concerned about the handling then the torque. And the look.. front hubs are harder to get to look good, unless you got a really thick rear hub it just doesn't look proportional ( personal preference ).

There's another problem with a high pivot springer fork that is unrelated to e-bike conversion, but exaggerated by a front hub motor. The direction of suspension travel is at more or less a right angle to the desired direction. So its suspension action is more or less worthless to improve ride quality or traction, even if it moves around a lot while riding. But it will articulate from motor propulsion force or motor braking force, inchworming the bike's wheelbase without helping its ride.

.. it does look cool though, reminds me of those old American choppers, Indians I think? Maybe Harley had it to I'm not sure not that much into motorcycles.

There's no practical reason the bike can't be electrified with a hub motor, front or rear, but the technical details would be much easier to resolve with a rear hub motor. Also the bike isn't intended for-- or any good at-- fast riding, so a low (ish) speed electric drive would be much preferable to a high speed one. A system that maxed out at 20 mph would be as fast as I'd ever consider for a lowrider bike, and even that speed might be pretty hairy.

Street legal here is 18mph and I wouldn't think it needed more either. It's something to be seen on, to see on it's own and not something to go fast or even look fast.

 

[2old]

I built my daughter a front hub, cruiser bike which she decorates for BM. I would put a "normal" cruiser front fork (preferably with brakes) on that bike and as above a 36V, 250/350w front hub system. If you insist on keeping the fork, a rear hub would work but check the dropout width berfor considering (or plan on spreading the frame).

 

[marvin78]

I don't think he's going to escape having to spread the frame.

 

[Brett1010]

Thanks guys - appreciate all the useful advice here.

I’ll definitely sand down the frame to see what kind of rust is going on there and will stick to low power / low speed on the back wheel.

Does anyone recommend any kind of low power conversion kit for this tire size that has long range?

 

[marvin78]

Many of the big box bso's which they electrify to sell to people wanting to own an 'ebike' are using rebranded xofo motors I'm told. I have one in mine, no complaints ( though not sure how long it will last ).

250W Open size 120mm geared motor-250W-Suzhou XiongFeng Motor Co., Ltd.-Suzhou XiongFeng Motor Co., Ltd.

Suzhou XiongFeng Motor Co., Ltd.

www.xofomotor.com

That's 125mm and I think the smallest dropout width and it's more then enough for a cruiser.. you can throw a 48v battery and they won't melt right away and go 40km+ ( 24mph+ ).

Not sure where you could buy them as consumer directly though, sorry.

edit: I don't mean you should throw a 48v on them, just that they seem to be pretty well built for what they are. Do as the guy below says.

*except for not restoring the bike properly, please give it some tlc and a new paint job ( so in 50 years people can still be looking at it ).

Or, if you do like the rust.. maybe clear coat it? That way the oxygen will be cut off and the rust would not progress.

 

[Slowchris11]

Range depends mainly on speed and your leg work. I would take a look at the maximum temperature the battery likes. I suggest it will be quite hot around there. A white case may help a little.
Running a small hub on 48V will probably melt it. These hubs are very reliable, used up to 15mph, then the problems start. You will use a throttle most of the time, this will make things even worse. Better go slow and get far... You will do 25 miles at 15mph, while the same battery may lasts 10 miles at 25mph.
Anyway, I don't think you will make a lot of friends, throwing sand around while blasting though crowds at 25mph...

About sanding the frame. I love the look of this evenly rusted bike. Consider leaving it as it is.
If you want to look for stability issues, lightly knock at the tubes with a plastic or piece of hard wood. You will hear if anything has gotten thin from the inside.

Install a tracker inside your battery, that way you will know where your bike ends up. Think of building some kind of small trailer with an integrated solar panel, for charging over the day. Electricity is not that easy to get at BM.

Some LED installation is a must for the night!

 

[ATinkerer]

The significant problem I see is brakes, or lack there of, if you use a hub motor.
All I can see is a coaster brake on the rear. If you replace the rear with a hub motor, no brakes at all.
Mid-drive? Don't know how a mid-drive will respond if you backpedal to engage the coaster brake?
Other folks have already mentioned problems with the springer front suspension and a front wheel drive.

 

[amberwolf]

I don't think he's going to escape having to spread the frame.

If it has a 100-110mm rear dropout (like some IGH frames) a front motor can be used in the rear, in a couple of ways.

The rightside cover can be removed, and replaced with a rightside cover from a rear motor of the same model, so it has the thread-on freewheel mount, and a single-speed freewheel can be installed. If no cover is available, the right side flange and thread-on mount can be cut off a standard bicycle hub, the bearing cup/mount removed, and it can then be bolted to the existing motor cover (with appropriate holes drilled in both for appropriate hardware). (I used this option for an old 9C motor used first on CrazyBike2, then later on the early SB Cruiser).

If the front-type motor has a disc brake rotor mounting point, it can be mounted backwards (rotor mount on the right) a sprocket can be directly bolted to that for a fixie bike, but the pedals will be forced to turn with the wheel all the time, so the rider has to be able to deal with that (not everyone can, though most should be able to, if it's geared correctly for the rider to pedal it up to the max speed of the system, which is usually low).


But...what brakes are going to be used? AFAICS it only has a coaster brake in the rear. A rear hubmotor will take that out, leaving no brakes. A front brake might be hard to directly add to that fork. There are add on rimbrake boss U shaped units, or you can cut one off a suspension fork and weld or hose-clamp it to this fork (I've done this successfully). Something similar can be done in the rear to give rear brakes.

There are also some types of calipers you may be able to fit on the front that ride on the central bolt above the fender. My experience with these isn't extensive; the only ones I've used like that have been on very old or very cheap bikes (or both), and did not provide significant braking; it could probably be improved in a number of ways if that turns out to be the only option, but I don't know exactly what those are.

A DD hubmotor can give you regen braking, but that's not usually a good replacement for physical brakes; it won't normally bring you to a stop, and it often has an upper speed (or voltage) limit, too, and most of the typical controllers only have on/off regen, with no control over amount of braking...which is usually insufficient to replace a physical brake anyway.

(you can get controllers with better braking options, but if anything goes wrong with any part of the system--battery, motor, controller, you then have no brakes).

 

[docw009]

Isn't Burning Man 2023 in about 3 weeks? You got a lot of work to do.

I'd go with a hubmotor with a squiggly ring painted on front. The videos indicate everyone just cruises along there at a few mph, and I thought most of the bikes ridden there are so worthless that they are thrown in a pile and left?
.

 

[Epithemeus]

I feel like a big part of the beauty of that bike is the ludicrous amount of spokes on the wheels. So I wouldn't do hub motor unless it was the only option. I think the tsdz2b mid drive has a coaster brake option and is relatively cheap. I'd be super sketched out relying only on coaster brakes though. Like I personally wouldn't go faster than a slow jog.

 

[Slowchris11]

This bike is not made for front brakes. The construction is too weak and the damper spring will extend during braking. Must be a funny feeling.
This is just like some Harley Davidson chopper, that only have a serious brake at the rear wheel. The driver is sitting far in the back, hardly any wheigt on the front wheel.

If the owner can weld, a disk brake at the rear would be the simplest solution, as all hubs have the holes. You have to build some simple steel part, screwed to the caliper adaptor. Then correctly position the caliper on the disk and place it so it has contact to the frame. Fix it there by pulling the brake lever. Tack weld the steel part to the frame, unscrew caliper, remove wheel and do the final welding.
Fitting a usual 135mm Hub will be no problem, the frames steel will flex, even better and permanent if you apply a little heat.

I agree with the spoke thing. Maybe a silver hub and some fake spokes, made from chromed plastic wire and epoxied in, could restore the look?
Also agree with the mid motor. TSDZ2 would even enable a coaster brake, but to fix it into the non standard frame, some metal work and welding will be needed as well. There will be some problems to get the chain line right.
The middle motor makes for a cleaner look IMO, as you don't need a separate controller. Just Motor, battery box and a very small display you can even put under the saddle, anything else optional.
Motor and battery have a high resale value and fit into your backpack, if you don't want to take the bike home...

 

[Chalo]

This bike is not made for front brakes. The construction is too weak and the damper spring will extend during braking. Must be a funny feeling.

Schwinn Krate models had front drum brakes on forks like that. The Atom drum brake they used wasn't a powerhouse, and maybe it did feel weird, but they sold a jillion of those things without incurring a stain on their reputation.

Also agree with the mid motor. TSDZ2 would even enable a coaster brake, but to fix it into the non standard frame, some metal work and welding will be needed as well. There will be some problems to get the chain line right.

Yes, all those problems, plus the fact that the frame uses an American bottom bracket shell which most mid drives aren't intended to accommodate, means a mid drive will be at best a kludge, without the advantage of multiple gears that's the only real advantage of a mid drive. This thing is a simple bike, incapable of high performance riding, and any e-bike conversion should likewise be simple and not too fast. That means hub or friction roller drive or maybe V-belt drive.

 

[marvin78]

Schwinn Krate models had front drum brakes on forks like that. The Atom drum brake they used wasn't a powerhouse, and maybe it did feel weird, but they sold a jillion of those things without incurring a stain on their reputation.

I like the big hub but the main appeal of the bike was in the spokes. 3 weeks doesn't feel like enough time to find a front hub with drum brakes which could use the same lacing pattern. But if you want functional over looks it's still period correct with the bike frame ( and since you're using a rear hub, you've already lost the rear wheel and it's beautiful spokes ).

Yes, all those problems, plus the fact that the frame uses an American bottom bracket shell which most mid drives aren't intended to accommodate, means a mid drive will be at best a kludge, without the advantage of multiple gears that's the only real advantage of a mid drive. This thing is a simple bike, incapable of high performance riding, and any e-bike conversion should likewise be simple and not too fast. That means hub or friction roller drive or maybe V-belt drive.

... friction roller... like a Solex? Now you mention that, this would look pretty sick. But that means adding a mount to the front fork, it will require some welding skills as you need to strengthen it most likely.

*kind of sad, I really like the form of that bike, even a friction drive would mean you'd need to butcher the fender. But it could turn out well I guess.

Just not seeing that happen in 3 weeks. Though with the things I'm hearing about throwing them on the bonfire I guess we're not going to see a lot of added manufacturing over 'just get it rolling'. Which makes me a sad panda

To to mid drive, well I can ride pretty well using only the 44t 13t with tsdz2, the only reason I shift is because I 'want' to ride a higher or lower cadence not because the motor couldn't pull it ( though I am a skinny dude so maybe the torque wouldn't be enough for someone heavier ). So maybe a fixie isn't out of the question if nothing else seems feasible. I was a bit afraid the housing wouldn't allow a flush mount due to the downtube angle but that shouldn't be an issue. No idea about an NA BB shell.

Imo, if given no time limit, I would not choose a mid drive because I would hope to find a hub which could be laced like the current wheels ( with shorter spokes on the motor wheel ) so to keep the theme of the bike in tact.

I'm trying to picture the frame with mid drive and it just doesn't feel that good.

I don't think this is a good '3 week quick project' bike, the bike deserves more ( imho ) and probably needs more for a proper conversion.

 

[Slowchris11]

Schwinn Krate models had front drum brakes on forks like that. The Atom drum brake they used wasn't a powerhouse, and maybe it did feel weird, but they sold a jillion of those things without incurring a stain on their reputation.

Sorry, you miss something.
If you would exactly compare the fork on you picture and the bikes, you could see that there is a grave difference.
Show a picture of the whole fork and anyone can see it at once.
Your brake fork is build on two tubes per side, giving it strength. The bike only has one, long tube, that is even weakened with holes to connect it and a kind of cork screw flat steel. You may not be an engineer, so let me explain to you. The fork will fail at this point if you pull the wheel forward. The cork screw part will not help in this direction as a tube would do, that resists to bending. It will indeed help a little more when braking.
This is cheap old steel tubing, not forged titanium. If you still don't understand, imagine taking away one of each sides tubes holding the wheel in place at the bikes rear end. then replace it with a rope. What kind of stability would be left? You are right: None. The bikes fork was build for show, not for function, maybe at a time when manufacturer where not sued for the harm their products caused or even by DIYS .
The bike's fork is weak and will bend with very little load, the owner can check this in a second.

 

[Chalo]

Your brake fork is build on two tubes per side, giving it strength. The bike only has one, long tube, that is even weakened with holes to connect it and a kind of cork screw flat steel. You may not be an engineer, so let me explain to you. The fork will fail at this point if you pull the wheel forward. The cork screw part will not help in this direction as a tube would do, that resists to bending. It will indeed help a little more when braking.

It's true that a springer fork isn't especially strong. I think that has less to do with the shape of the truss elements (though the twisted flat steel surely doesn't help compared to a tube) and more with the entire fork structure attaching with a single ~3/8" bolt, usually mild steel, that pokes through drilled or punched holes in squashed mild steel tubing and articulates without a bearing of any kind.

Despite shortcomings, despite the fact that they don't work all that well, this is a fork style with a long history and millions of examples. Its failure modes tend to be more progressive than those of a monolithic conventional fork-- it becomes wobbly or crooked and then gets stashed in the shed indefinitely, rather than breaking off and precipitating a personal disaster. I doubt that putting a drum brake or low powered hub motor in one will change that general pattern. Even a high powered hub motor tends not to exert as much force on the fork as a decent brake, and we know from lots of other people's experiences that such forks can tolerate brakes at least somewhat.

I like the big hub but the main appeal of the bike was in the spokes. 3 weeks doesn't feel like enough time to find a front hub with drum brakes which could use the same lacing pattern.

Lowrider bikes customarily have 72 to 144 radially laced spokes. A 36 hole hub motor can have extra holes drilled in the hub flanges between the original holes, and chrome steel rims are available already drilled for the higher spoke counts. Because the primary purpose of a lowrider bike is personal expression, there's a robust supply of spare parts for custom work.

72 or 144 spoke bicycle wheels are often referred to as "baby Daytons" after the Dayton brand wire wheels used on lowrider cars.

 

[CONSIDERABLE SHOUTING]

Depending on what you're willing to spend (say, if you used an ESC to run a small hub motor) you could brake using regen. If you seriously doubt you'll be going anywhere fast, that could be a great option and keep you from having to fabricate something.

 

[nicobie]

I think the best thing for that frame would be a rear mounted friction drive. Too cool.