Gazelle Chamonix conversion

[jonescg]

Hi All,
So I will be convering my wife's step-through Dutch bike (aka tall person's bike) to electric. She's got an electric ladies bike but doesn't ride it much as its not exactly a sturdy machine for longer trips. The Gazelle frame always suited her as she's quite tall, but it was never an electric bike. It's got a hopelessly inefficient gear hub in the rear which I might just replace with a single speed set for a comfortable cadence.


Now that we live in the Perth hills, an e-bike is kind of essential for travelling further than the local market, so I'm aiming for a 500 W direct drive hub motor in the back with a frame mounted battery pack. I might mount the speed controller behind the seat or something.

Direct drive is essential as we need to take advantage of the regen braking. These bikes had brakes which were painted on, presumably because they never went faster than 20 km/h on flat ground. I don't think the front brake is all that flash, so I might try and see if there's a better option on the market.

I bought about 50-odd Molicells for testing. They're an honest 4 Ah, and 3.7 V with litle sag. I'm building a 48 volt, 17 Ah, (14s,4p) pack using the same capture plate method I used for the Prelude battery build. 0.9 mm thick copper busbars jetcut with nickel tabs soldered to them will make assembly easy, and they should be capable of sustaining 80 amps continuous (5C). Which is quite likely given the 10 km, 250 m elevation gain at the end of the day. She'll probably need to charge the bike at work, but that's no big deal - I want to make the battery as easy as possble to remove and charge remotely.


The machined polycarbonate plates have provision for copper busbars to be folded inwards and terminated internally using 8 AWG (13 mm2) wire and lugs, while a sandwich of FR4 and thermal epoxy will finish the outside. I might 3-D print some brackets which allow me to drop it right into the frame vee without too much fuss. Maybe something as simple as a strap to hold it down?

The current path is a bit convoluted, but the least-worst arrangement I can devise given the shape.



Will keep you posted!

Chris

 

[99t4]

What are the current brake pads? Why not try some upgraded brake pads first?

If you go with a rear dd hubmotor you will lose the 3-spd IGH anyway.

What are you going to use for TAs?

 

[jonescg]

Current brake pads are whatever the bike came with standard, so probably nothing special. From memory they are the spiral mechanism ones. Definitely not hydraulic.
The rear hub should have enough torque to carry her up the big hill but the exact gear ratio will probably be optimised for a natural cadence. Last time we had big power ebikes we only ever rode them in top gear and used the throttle to launch.
Sorry, what's a TA?

 

[99t4]

Sorry, what's a TA?

Torque Arm, to prevent dual-flatted axle spinout in the dropouts:
https://ebikes.ca/product-info/grin-products/torque-arms.html

About the brake pads-- try genuine koolstop salmon before ripping everything out.
https://endless-sphere.com/forums/viewtopic.php?t=40910

Also, running dd hub gives you the option of regen braking.

 

[jonescg]

Ah. Yes will definitely be using torque arms. Big hubs can very easily do a number on a dropout.

Thanks for the tip on the brakes. The front wheel will probably retain the current calliper but more fricticious pads will help. The hub will definitely have regen, but I need to find a friction option too, and I doubt the existing pads will line up.

 

[E-HP]

Ah. Yes will definitely be using torque arms. Big hubs can very easily do a number on a dropout.

Thanks for the tip on the brakes. The front wheel will probably retain the current calliper but more fricticious pads will help. The hub will definitely have regen, but I need to find a friction option too, and I doubt the existing pads will line up.

You could use the existing rim and they would line up for sure, or if you're sticking with the same wheel size, then there should be no issue as well.

 

[jonescg]

Having now looked at the bike, its got silly drum brakes and no discs. This won't be easy or cheap...

 

[Chalo]

Having now looked at the bike, its got silly drum brakes and no discs. This won't be easy or cheap...

I think you mean very low maintenance, all weather brakes instead of easily contaminated and bent discs.

This seems like a good candidate for a front hub motor with a Rollerbrake spline, so the brake can use the same fork fitting.

https://bafang-e.com/en/oem-area/components/component/motor/fm-g320250r/

Someone is selling wheels with these for $40 plus shipping on eBay, but they're in Houston.

https://www.ebay.com/itm/363614574558

 

[99t4]

Wait-- did you bait and switch the photo in your first post? I distinctly remember cantilever brakes on the bike in that photo... :?

 

[jonescg]

Yeah sorry I did switch the image. I only got a chance to take a look at the bike yesterday where I learned its the Chamonix Pure which has drum brakes. The front wheel can stay exactly as it is, brakes and all. But the rear wheel which is getting the hub motor will need a new brake calliper assembly.
Also the motor needs to be pretty beefy as the 10 km, 250 m elevation gain is quite steep in parts, so I doubt I can get away with a single speed.

 

[jonescg]

Think I'll abandon this project before I even get started. The Gazelle Chamonix Pure has to be the most badly engineered bike ever. It's almost impossible to service; a flat tyre means the bike is in a million parts before you even put a tyre lever to it. So many captive nuts, unique fittings, and intermeshed components...
I reckon I might be buying a decent bike instead

 

[jonescg]

OK, some redeeming features...
The drop outs are 135 mm, so they can be stretched a bit to fit the rear hub. The front chain ring is a 38 tooth, fairly thick sort of a ring too, as the chain looks to be quite wide. This means a sensible cadence and reasonable flat ground speed means I'd need to fit a 12 tooth cog, which seems... unlikely? I think 14 is about as small as they get, so changing the front chainring seems necessary.

Rear brakes are still an issue. I might be able to get a bracket machined to suit a conventional disc calliper and fit that to the left side dropout.

 

[99t4]

Rear brakes are still an issue. I might be able to get a bracket machined to suit a conventional disc calliper and fit that to the left side dropout.

When it gets to that point, that's when to start looking for another (better suited) candidate. Really it depends on your fabrication skills and desires.

There are no large framed step-over common component bikes in your area that would make a better starting point?

 

[jonescg]

Decided to make a go of it. I took the crank and chainring off, bought a DD hub motor and fitted the brake disc and an 8 speed cluster. I'm yet to find a suitable crank and chainring, but will look for something in the Fixie world.




The hub fit nicely after stretcing the frame a little, and I reckon with some clever fabrication I can make a decent sort of a fixing point for a read brake calliper.




I might need to fit a deralieur yet - not sure what ratio is ideal for a typical cadence, but it's not the kind of bike you'd get up and churn on. I suspect the motor will be doing a fair bit of the work.

 

[99t4]

Nice. :thumb:

Depending on the power you are going to be running, don't forget the Torque Arms.

Fortunately, you have large flat dropout geography there, so something simple like Grin TorqArm_V2 might work, minus the additional slider plate.

https://ebikes.ca/product-info/grin-products/torque-arms.html

 

[jonescg]

I need to fabricate a derailleur hanger on that side anyway, so I might as well incorporate the torque arm into it.
On the other side, the disc brake calliper needs an adaptor of some persuasion made, which I can probably get machined out of 12 mm aluminium. Time to get drawing!

 

[jonescg]

I'll try and 3D print this tomorrow and see how it looks. Might need some adjustment.

 

[jonescg]

Few minor adjustments, but that's pretty darn close.

 

[jonescg]

Bit of steel, some drilling and tapping...

 

[jonescg]

Some progress today - seems to work quite well. Eventually we;ll get a controller capable of regen so the brake pads last a little longer.
[youtube]lBr_VIpSUYg[/youtube]

 

[99t4]

Looking very clean :thumb:

Still going with the plan for the battery down in the "V" of the frame?

 

[jonescg]

Looking very clean :thumb:

Still going with the plan for the battery down in the "V" of the frame?

Yeah, it's too easy to pop a wheelie / damage the rim with all that weight over the back. It's not as nice to step over, but the bike will handle a lot better.

I tightened things up and went for a quick spin with the battery strapped to the back. Goes like a shower of shit and so smooth too. The motor controller doesn't have regen, but at this stage it's not a big deal since the new disc brakes are pretty stoppy. The current gearing has it sitting on about 1 pedal = 3.2 revolutions of the wheel, so a comfortable cadence = 25 km/h, which is spot on for the roads around here. Any faster it shakes up too much.

She hammers up fairly steep inclines at 35 km/h if you're keen, so I don't think I'll be too fussed about finding a gear shifter at this rate. Only reason you need them is for when the battery goes flat and you need to pedal home. Time to find some brakes though That roller brake on the front is painted on...

 

[calab]

I like the way you made a torque arm and a hangar one piece out of steel.

I like front hub setups, its not ideal but for me it takes away many flats and many broken spokes.

 

[Chalo]

Time to find some brakes though That roller brake on the front is painted on...

BR-IM70, IM80, and IM81, or BR-C6000, are all wildly more effective than what you have there. Also, like all drum brakes, Roller brakes are finicky about lever pull ratio. Avid Speed Dial (with the mechanical advantage turned all the way up) or an old Shimano Servo Wave lever, with long lay "compressionless" brake housing, should get the best from any drum or Roller brake.

As for me, I would have solved that problem first, and then found a front hub motor with a Roller brake spline on it.

 

[jonescg]

Minor update - managed to install a basic 5 speed shifter which works well enough for when the battery is flat and you need to ride it home. Unfortunately the cable is about 100 mm short but it works.

I'm going to fabricate the rear disc brake calliper bracket from steel - way cheaper than CNC ally anyway.

I'll leave the current front wheel as it is, but my intention is to install either a horseshoe rim-brake calliper in place of the headlight, or at worst, devise a disc brake calliper to suit the front. At least it's pretty close to operational