First Conversion: Looking for advice

[Shcootr]

Hello this is my first time posting. I picked up a vintage motobecane super mirage (I think from the 80s) and would love to be able to commute on it to and from work. I've tried going straight leg power, but being in Seattle we have plenty of hills so I'm looking for a little electric assistance and would love some advice on where to start. From what I've found already, seems like mid-drive motors might be my best bet for preserving the look and function of the base bike, but I worry a bit about putting too much stress on an old driveline.

Details:
- Commute is 13 miles each way (though I usually take the bus for at least half of it), I can recharge at work easily
- Hills are fairly constant but I only have one nasty one around 5% grade and I like the idea of a throttle I can toggle if I feel like I need help (would love to be able to go raw leg power if I desire)
- Don't need much speed, 25mph max is probably good enough
- I am an engineer/machinist, so I'm confident in the DIY portion and would love a fairly involved project

Thanks!

 

[glennb]

Mid-drive is an over complicated solution for your use case. You're right to be concerned about it.

Your rear will be 126mm, which is a tad narrow for a rear motor, presuming you want to retain use of rear gears.

Front hub is the obvious solution, especially since you have a steel fork. Just about any hub motor will work for you. Bafang G311 is best in class, but AKM-100 is worth a look too, as are others.

Best approach is to settle on a motor model first, then work backwards from that to select appropriate motor wind (rpm/volt), battery voltage/capacity, then lastly a controller that suits your needs and budget.

 

[stancecoke]

for this classical bike, I would recommend a maximum stealthy conversion. The Yose A3 kit has just the bottle battery with the integrated controller and one cable to the motor and offers a much better ride experience than simple PAS or throttle systems due to the cassette integrated torque senosr. The A3Pro set comes with an additional plug, that can be used instead of the display.
But as @glennb mentioned, you would have to widen the rear triangle to 135 mm. Should be feasable for a steel frame, I think.

 

[glennb]

Yes, cold setting the frame is simple, and torque-sensing should be seriously considered.

If the shifters and drivetrain are in reasonable condition you could retain them by making a custom 6sp cassette. Not something I'd normally advocate if it's a 52-42 front double, but with a motor it's acceptable gearing.

Or is it 7sp? If so, even easier, no customisation required, you can happily use 7sp cassettes.

25mph could require custom firmware though

Or strong legs and lungs.

 

[highlandr]

How important is noise? I was attracted to mid drives initially, but even the quietest ones don’t compare to a DD hub. I really appreciate my silent DD hub compared to the mid drives I have ridden. But I would say I’m overly sensitive, many people don’t care.

 

[99t4]

I picked up a vintage motobecane super mirage (I think from the 80s) and would love to be able to commute on it to and from work.... 25mph max is probably good enough

Riding a skinny tire non-suspension bike under pedal power is one thing but once you start reaching into the 20 MPH range the bumps and potholes change from annoying and mild uncomfortable to dangerous and crash inducing. But maybe your route is nicely paved?

In case you haven't seen it, here is some good introductory reading material for you:
DIY Newb FAQ?

 

[Shcootr]

Mid-drive is an over complicated solution for your use case. You're right to be concerned about it.

Your rear will be 126mm, which is a tad narrow for a rear motor, presuming you want to retain use of rear gears.

Front hub is the obvious solution, especially since you have a steel fork. Just about any hub motor will work for you. Bafang G311 is best in class, but AKM-100 is worth a look too, as are others.

Best approach is to settle on a motor model first, then work backwards from that to select appropriate motor wind (rpm/volt), battery voltage/capacity, then lastly a controller that suits your needs and budget.

This is good info to have, one general question though: for the most part my commute is pretty flat and I only really need the assistance for hills, do the hubs let you toggle assistance on and off? @stancecoke was saying that hub will give me a better ride experience than a throttle, I'd been drawn to the throttle so I could choose when to help myself out.

I'm also a bit of a newb for general bike things so am not sure how to tell what condition everything is in. Was planning on taking it to my local bike shop and seeing what they think it could take

 

[Shcootr]

How important is noise? I was attracted to mid drives initially, but even the quietest ones don’t compare to a DD hub. I really appreciate my silent DD hub compared to the mid drives I have ridden. But I would say I’m overly sensitive, many people don’t care.

Doesn't matter at all to me, normally I've got music playing in at least one of my ears since I don't need to ride on the road. Benefits of dedicated bike path to and from work

 

[joha]

Hello this is my first time posting. I picked up a vintage motobecane super mirage (I think from the 80s) and would love to be able to commute on it to and from work. I've tried going straight leg power, but being in Seattle we have plenty of hills so I'm looking for a little electric assistance and would love some advice on where to start. From what I've found already, seems like mid-drive motors might be my best bet for preserving the look and function of the base bike, but I worry a bit about putting too much stress on an old driveline.

Details:
- Commute is 13 miles each way (though I usually take the bus for at least half of it), I can recharge at work easily
- Hills are fairly constant but I only have one nasty one around 5% grade and I like the idea of a throttle I can toggle if I feel like I need help (would love to be able to go raw leg power if I desire)
- Don't need much speed, 25mph max is probably good enough
- I am an engineer/machinist, so I'm confident in the DIY portion and would love a fairly involved project

Thanks!

Hello and welcome! It's my first time posting too and I ran into your post and I hope I can help you from my experience, since I converted my bike too. So i believe that for your needs a hub motor can work perfectly fine, for example the kit I use allows to switch between pedal assist mode and throttle and was very easy install for me and I'm far from being a engineer hahah so I'm sure it won't be a problem for you

 

[glennb]

This is good info to have, one general question though: for the most part my commute is pretty flat and I only really need the assistance for hills, do the hubs let you toggle assistance on and off? @stancecoke was saying that hub will give me a better ride experience than a throttle, I'd been drawn to the throttle so I could choose when to help myself out.

I'm also a bit of a newb for general bike things so am not sure how to tell what condition everything is in. Was planning on taking it to my local bike shop and seeing what they think it could take

You can ascertain chain wear with a ruler.

With a good torque sensing setup you likely won't desire a throttle. But with whatever you choose, you might like to select a low baseline power level, then increase it on inclines. For that, if they're just short sharp rises, it can be more convenient to apply throttle than to toggle between power levels.

Probably best to test ride a few different systems if your bike shop allows that.

 

[neptronix]

What is your maximum budget?

 

[docw009]

Don't need much speed? How fast do you want to cover those 13 miles to work? Might be a problem for other riders if you want to ride 20+ on a bike path,

Most of my converted bikes have a practical throttle speed of 20-22 mph on 48V, but I'm sitting up blocking the wind. On your drop bar bike, I could get 25 mph with a 500W hubmotor. Suggest a 25A controller though,

My first conversion was a 500W rear hub with 22A controller on 36V. The cadence pedal assist was overboosted, but I got used to it. Installed in a steel frame Trek 800. I recall spreading the rear dropouts a bit with an auto jack. It topped out around 20 mph. After 10 years, I upgraded to a 25A controller/48V, It maxes out around 24 mph on throttle only. That's how I estimate top speed. A stronger rider could go faster by adding in some pedal effort.

Geared hubmotors with cadence sensor have no pedal drag because of the overboosting. They might coast a little slower, but only a roadie could feel it, Midmotor kits feel pretty light too. Both will feel heavy if you and your bike are like a truck.

My preference these days is the $280 Tong Sheng TSDZ2B torque sensing middrive kit. It sucks unless you change to 3rd party firmware, but after figuring that out I'm good with them. We have two as daily riders and I put away a spare motor. The $400 toseven DM02 mid drive rides the same out of the box w/o any re-programming, but its throttle is more for holding speed. It doesn't have much acceleration, For aesthetics, the motobecane would look good in a mid drive, but a lighter hubmotor will work.

Here in the USA, the Yose torque sensor hub motor kit mentione above isn't readily available. I would say it won't meet your speed aspirations.

 

[stancecoke]

Don't need much speed, 25mph max is probably good enough

most part my commute is pretty flat and I only really need the assistance for hills

This is a contradiction.

25mph is 40kph, that's pretty fast! You will need about 450W to reach it on the flat with your type of bike. If you push 150W yourself, the motor has to deliver additional 300W. This is no problem for a common hub motor. But you have to look for a motor that has a sufficient max speed at your battery voltage.
I would never ruin such a beautiful bike with an ugly middrive motor!

Probably best to test ride a few different systems if your bike shop allows that.

This is the best recommendation