Advice for 20" hubs.

vfr400

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The Apollo Transition bike is a machine I know quite well, simple inexpensive and perfect for nipping round Tesco's and picking up the kid's from school, conversion to an e-bike, well that's a different matter.
The mechanical stresses on a folding bike are very different to a traditional diamond frame for starters, where would you say the weak point is on a folder...the hinge ? Folding bike enthusiasts reading this will know it's not so I wont go into the stress dynamics of the frame regarding shearing and torsional forces.
The Transition is a bike built to a price point...cheap, hence my reference to it's cost. As such it flexes creaks and groans which makes it entirely unsuitable for converting to an e-bike bearing in mind the extra stresses it will encounter.
Could it be done ? yes easily I'd say, I believe someone fitted a ram-jet to one once ! but IMHO the answer is don't.
I'll look forward to the 1000m review ;)
There isn't realy any extra stress because the motor is in the back wheel. The rear triangle will easily be strong enough and the torque from the motor only reduces the stress on the folding mechanism. I thought you'd have figured that out.
 

Benjahmin

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Thanks vfr, I now see that the chain whip is actually a fitting tool not a removal tool, and why would you need one anyway when you can stand on the peddle. I'll get the back wheel out and see which I need.

I did wonder about the 260rpm, I've seen 328rpm motors for 20" wheels, just can't remember where.
Just found it, it's the Q100CST on BMS. I guess that's for cassette and it's less powerful.

Torque arms, absolutely. I like these, similar to what cyclezee used to do.
https://www.ebay.co.uk/itm/Torque-Arm-e-bike-Heavy-Duty-Stainless-Steel-14x10mm-electric-bikes-ebikes-/153380848840
 

RossG

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Feb 12, 2019
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C'mon vrf you're old school like me, you know full well where the max stress is on a folder and it's definitely not the hinge. You wont have to figure that one out...you already know (nice try though).

Incidentally I got my first folder in 1973 because my GF had one, she hit the roof! Mine was brand new, her's was an old Raleigh her mum got her S/H, do you know she never forgave me for that...true story.
 

harrys

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Dec 1, 2016
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Harrys, it's 20" both ends. I said the wheels only have 26spokes, perhaps that's the confusion.
I see that now. A quirk of the lens which makes the front wheel look smaller also confused me.

I have the Q100H 260 rpm motors (36V) on our folders. Bought bare motors from BMSbattery to save on shipping. Spoked them into 36H rims with Saphim Strong spokes which are 13G at both ends and 14G in the middle. Didn't save much money, but I feel it's a better wheel. I use DNP 11T-30T freewheels

The motors have a foot long cable with 9 pin connector, The provided extension is 4-5 feet long with Hall plug and bullets to fit controller.

36V/48V 22A KT-controllers (square wave) from PSWpower. Kits include LCD, brake levers, throttle, PAS sensor, speed sensor. You don't need the external speed sensor as the Q100/Q128 motors have an internal one already wired to the 9 pin cable. You will have to move the KT-controller's speed sensor input to the Hall connector. I put the controllers under my racks.

My wife's bike uses a 36V 9AH 10S-3P battery with Samsung GA cells. Fits in bag under the seat. My bike uses various packs. I like to use a 10S-2P 36V4AH hoverboard pack under the seat, with a spare in a handlebar bag. I often put two of these packs in parallel (makes 8AH) in a bag on the rack. I also have a 52V6AH 10S-2P pack that fits in the seat bag. I'm looking for a non-ebike appearance, and the smaller packs keep the weight down. I get 35 pounds and 38 pounds on our bikes with batteries.

The bikes are geared for about 17-18 mph with fast pedaling. The motors can drive them close to 18 mph. A 4AH battery can get me 14 miles reliably in nice weather at 13 mph, i.e. an hour of riding.
 
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harrys

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C'mon vrf you're old school like me, you know full well where the max stress is on a folder and it's definitely not the hinge..
I thought it was the hinge, but glad to know that I'm wrong. Is it the weld where the downtube meets the head tube, given that most folders have no top tube.

Our folders. Mine is the yellow.
P1080129.jpg P1080130.jpg
 
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vfr400

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Jun 12, 2011
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On the subject of conversions....how not to do it.
Guys like that are dangerous. He's got a thin aluminium rack between his frame and axle on a full suspension bike, and he has four SLAs sitting on it. As soon as his axle starts going up and down, it'll shake the rack to pieces and his batteries are going to get spewed all over the road.

I was going to message him about it, but then spotted that he had a follow-up vid, where he said he'd had a lot of messages about it and admitted that he hadn't gone far on it, but he still didn’t see it as a problem!
 

RossG

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Feb 12, 2019
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Yeah.. I though that vid would go down well, at least the chap's still in one piece. I hope his bike is !

@ Harrys

Ah, I see you have a couple of Yans bikes good choice, didn't realize you were in the states. He certainly knows how to design a good bike, rock solid no problem powering them up. I used to chat to Yan back in the days of the 'Great Tern cracked frame debacle' That changed the way folding bike frames were made.

As for frame stress.... when you press down on the pedals of a bike the whole frame distorts but a traditional diamond configuration handles it perfectly, it's the ideal shape hence it endures to this day.
With a folder things are different, with no top tube all the stress is torsional along the tube connecting the front wheel to the back, a folder literally twists along the frame.
Imagine taking a long solid rubber tube and twisting one end one way and the other end the other way, that's what's happening with a folding frame. Now the rear section is strong with not much movement because it usually has it's own small triangle as Neal rightly pointed out. The front end however has little or no bracing so the whole frame tube twists in relation to the rear section. Now consider this, the main tube isn't one whole solid section as it's a folder so flexing cannot be absorbed readily in the rear half of the bike. The hinge has to take all that torsional twisting force. ok, so how come it's not the Achilles heel ? Well you can make a hinge as strong as you like on a folder but it's still all down to the welds and how the frame tubing is connected to the hinge itself that matters.
The weak point is that weld that joins the front section of frame tube to the hinge, if something gives you can be sure it will be there. That's why Tern had to do a recall on thousands of it's frames thanks to design & weld problems. I'm pleased to say I played my part in that but I don't expect a Knighthood from the Queen !
These days folders are much stronger, hinges and frames are better designed at the fold with internal raised sections and indents that lock together to keep the hinge more rigid, internal abutments in the frame tubing by the hinge and extra material welded to the frame around hinge to create a greater weld section. Better hinge bolts and latches all make for a safer folding bike, that's why I still maintain it's all down to cost. Cheap bikes just don't have that attention to safety detail that the more expensive machines possess , and hence IMO at least don't make ideal candidates for conversion to e-bikes.
 

Benjahmin

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Seems to me that you've just made the best arguement FOR converting these bikes.
The motor in the rear triangle will put a rotational force onto the dropouts but will be spread by a torque bracket. This force will have a steady nature, not the pulsing nature that comes from the rider pedalling. That force will still be there, of course, but my guess is that it will, mostly, be lower, only maxing out on hills.
As to the oscillating strain put on the hinge and welds - I see your point. However the design can either take this or it can't. If anything, adding a rear motor serves to alleviate some of this strain as the rider does not have to work so hard.

This is not a commercial conversion, it's favour for my neighbour. The bikes will spend most of their time folded in the garage of his camper. Used mostly for river/canal path rides, with the odd jaunt into town for a bottle of wine and a baguette. Purely leisure rides with nowhere to be at any time and no point to prove. The conversion is going ahead subject to final parts selection.

Ross, your investigation on the suitability of folders, in general, for conversion may well have merits beyond my scant engineering knowledge. But this is a thread asking for component advice, please start a thread where the engineers can present cogent facts to each other. I will read it with interest.

For myself, I would never have a bike with anything less that 28" wheels. I just can't take them seriously:oops:. Folders have never appealed or been needed. So 700c and double front ring all the way for me.
 

Benjahmin

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Now I've got the rear wheel out (so I can order a freewheel removal tool) and I see that the dropouts are 130mm. Can anyone confirm if a Q100H will fit? I seem to remember standard dropouts being 140mm. As the rear triangle is so short I can't see this springing a whole 10mm.
 

vfr400

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I've never had one that didn't fit, but those folders with a big fat seatstay that curves round from the main spar can be very stiff. Yours will be OK. No disc brake saves you about 5mm because you don't need the spacing to keep the disc away from the caliper and stays. You can reduce the motor's width with a narrower freewheel, like a 5-speed one. How many gears are you planning?
 

Benjahmin

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It's got 6 on it with a twist grip changer. Frames aluminium whereas the forks are steel, so a front hub is still a possibility.DSCF3197.JPG

DSCF3198.JPG

So I've got about 11" to spring 5mm/side. I can do about 4mm total with my hands, think it'll go?
 

RossG

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Feb 12, 2019
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I might be a pain in the R's I'll admit that , but I'm also a responsible pain and I have to say springing aluminium is a no no. I'll leave it to the experienced guys to tell you why that is.
 

vfr400

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I'm an experience guy and I'll tell you it's absolutely no problem to spring an aluminium frame. The only time I've seen problems mentioned is on forums, where the theorists, who never tried it, do their scaremongering. It's another urban myth. With a 6 speed freewheel and no disc, your motor will be narrower than normal.

Just about every bike with a Q100 or the even wider Q100C had to have its frame sprung a bit to get the motor in. Have you ever heard of someone that broke their frame because of that? In fact how many broken frames for anything can you remember? About 3 or 4 in ten years is my count. One was a Haibike with a broken suspension bracket and the other three were all broken seatposts due to dodgy design.
 
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Benjahmin

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OK, so there's a difference of view on the flexibility of aluminium, I've heard that ally frames give a harsher ride because of it's lack of flex. Can't say that I've noticed.
The issue here is, am I going to be able to get the motor axle inbetween the rear forks. I can see how not having a disc makes the motor less wide, but I'm not clear how that would affect the axle length. Is it because there are spacers or nuts that can be removed from the axle?
Obviously I've got to be uber careful here because it's not my bike and I also don't want to end up with two kits I can't fit.
Thanks for all the help guys.
 

RossG

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Feb 12, 2019
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No offence intended and I hope none taken but I have to say vr's advice on ali frame springing is incredibly irresponsible.
Aluminium has an almost crystalline structure, it's soft but not malleable as such, that means when bent it actually cracks which results in the material eventually falling apart. Have I known it to happen ? dozens and dozens of times. No so long ago a pal of mine had a near miss when we were coming down a really steep hill at nearly 40mph and an alloy bracket he'd fashioned gave way (stress fracture) and almost went into his front wheel, a real close one that. You also risk fatiguing the welds holding the rear triangle together, it happens to planes all the time that's why they're constantly X-rayed. There's a saying in the cycle world when it comes to frame springing ' Steel, sure, Titanium yep ok, Aluminium..never ! ' Don't believe me ? Google is your friend.
Incidentally I've been cycling for over 65 yrs (gulp) that doesn't make me a genius but it does indicate a tad of knowledge. Bending aluminium to suit something it was never meant do:eek:, this should be an enlightening thread.
 

vfr400

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Jun 12, 2011
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No offence intended and I hope none taken but I have to say vr's advice on ali frame springing is incredibly irresponsible.
Aluminium has an almost crystalline structure, it's soft but not malleable as such, that means when bent it actually cracks which results in the material eventually falling apart. Have I known it to happen ? dozens and dozens of times. No so long ago a pal of mine had a near miss when we were coming down a really steep hill at nearly 40mph and an alloy bracket he'd fashioned gave way (stress fracture) and almost went into his front wheel, a real close one that. You also risk fatiguing the welds holding the rear triangle together, it happens to planes all the time that's why they're constantly X-rayed. There's a saying in the cycle world when it comes to frame springing ' Steel, sure, Titanium yep ok, Aluminium..never ! ' Don't believe me ? Google is your friend.
Incidentally I've been cycling for over 65 yrs (gulp) that doesn't make me a genius but it does indicate a tad of knowledge. Bending aluminium to suit something it was never meant do:eek:, this should be an enlightening thread.
This is what they say every time someone mentions stretching a frame to put in a motor. Nobody has broken one yet.
 

RossG

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'There's always a first time' Besides do we know for sure no one has. Springing won't necessarily crack a frame in an instant, what it does do is weaken it's integrity. So you get some underwear but it's too small...no problem it'll stretch with wear, of course it will, but what happens to the elastic ? ok hardly the same thing but you get my drift.
Fact is if you stretch aluminium it compromises it's integrity, that's not me thinking out loud because I'm bored it's a scientific fact. Can't change the laws of physics I'm afraid.
 

Woosh

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Fact is if you stretch aluminium it compromises it's integrity, that's not me thinking out loud because I'm bored it's a scientific fact. Can't change the laws of physics I'm afraid.
Aluminium 6061 has an ultimate tensile strength of at least 290 MPa (42,000 psi) and yield strength of at least 240 MPa (35,000 psi), Young's modulus : 68.9 GPa (9,990 ksi) Elongation at break: 12–25%.
The last bit (12% elongation before break) is an important point.
When you spread 5mm on a 20"wheel, the maximum elongation of the tie at the weld where the two branches of the rear triangle are tied together near the bottom bracket is roughly (5mm/130mm) * (100mm/250mm) = 1.5%. It's much more than spreading 5mm on a 26" or 700C frame. However, it's not a huge risk.
 
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Benjahmin

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WOW!
This is getting way beyond my pay grade.:oops:
I know that aluminium stress fractures, on repeated bending, easier than steel. But this will be a static bend, won't it? In other words once the stretch is made it stays there (the 140mm axle holds it apart) it's not a repeated action.

I don't know how you derived that formula Tony, but I assume that the 250mm is the measurement from dropout to the chainstay tie. If so, then the actual measurement on this bike is 270mm. When I plug this into the formula I get 1.42%. I know - confirmation bias:( (By the way, neat maths for a quarter to six in the morning. Is that before or after coffee?)

I do see your point Ross. Intuitively I know that aluminium is not as maleable as steel, otherwise I wouldn't be hesitating.
I think all I can do at this point is talk to my neighbour and see if he wants to take the risk or not.
There's always the front hub option.
 

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