Motobecane 40T Moped conversion

[northernmike]

Greetings! Taking inspiration from nasukaren, I'm converting my gas moped to electric drive. Here are a few pictures. I've ordered the same HXT motor as she is using and will be starting with SLA batteries. Though not shown in the pictures, I've converted my headlight and tail-light to LED bulbs already and mounted a Magura 5k potentiometer throttle control. Tires are 17 x 2.25 SAVA, a little oversize for this bike, but a nice supple ride.

My plan is to use a belt drive, direct from the motor to the reduction pulley. This feeds the chain-drive to the rear wheel and is used to receiving (I believe) up to about 4,000 rpm from the 49cc 2-stroke. I have a few different chain drive sprockets to play with to adjust the final ratio and will be looking into an appropriate pulley for the motor shortly.

The motor mount will incorporate the shock-absorbing rubber isolation of the Motobecane design, and will likely use support bearings on each end of the shaft to accommodate belt tension without undue stress on the HXT. I am toying with the idea of incorporating the Motobecane "Variator" transmission - a centrifugal clutch based CVT mounted on the motor shaft - to improve acceleration and to reduce the load on the motor at take-off.

Your thoughts and assistance are needed, and appreciated!

Regards,

- Mike

 

[oofnik]

Wow Mike, the Moby is in excellent shape!
I've toyed with the idea of converting my Puch Maxi... but I just don't have the funds or the time to do it the way I want to do it. A project of this magnitude is just no fun if it's under-funded.

As far as keeping the variator, I think that would be an excellent idea. You would get ridiculous starting torque plus a very comfortable (if not scary!) top speed.
Could you expand a bit on how the original engine drives the variator? Is it just a V-belt reduction?
What kind of range are you looking to achieve?

I am really interested in following this project and would be more than happy to offer my opinions along the way!

 

[northernmike]

Here is the Variator. It attaches, though, to a tapered & threaded shaft ... I'd have to somehow mate the 12mm motor shaft to this, and I'm not sure where to start.

Though it did provide great performance with the gas motor, I'm leaning towards a fixed pulley for simplicity.

The bike was repainted by it's previous owner, and looks a bit different now - the rack is back on the rear fender, I'm thinking I'll have to make or purchase some panniers for battery stowage.

 

[oofnik]

Is it a tapered shaft with a woodruff key and lock nut? Both the flywheel and the clutch on my Maxi are attached to the crankshaft in this manner. If so, it shouldn't be too difficult to have a taper adapter machined that would fit over the motor's shaft, allowing allow you to mount the variator drive pulley to it. I hope you have access to some machinery for this project - it would be next to impossible to do without! :?

Since the variator is already on the bike, I would strongly recommend using it. You will lose a lot of performance if you choose to fix the ratio in my opinion. Variators are the best thing that happened to those little machines. While they are much more helpful for a combustion engine (especially 2-strokes which have a very defined power band), they can also help you off the line and keep the wear down with an electric motor.

Also, this link may be of assistance. Moped Army has some great information on many mopeds.

 

[northernmike]

oofnik,

It was an AV7, so a tapered shaft w/o woodruff key. However, the Variator on a Moby is on the motor side, unlike the Vespa Boxer. Mobies are quite unilke Pooks. The engine swivels on a rotating top mount against a sprung bottom mount, providing belt tension for the CVT. I would have to engineer the whole thing... which could be fun! The variator was sold with the engine, but I can get another.

I rebuilt my variator myself, loosely following the procedure you mentioned and linked (thank you), about a year ago. (I have the same username on MA.) The bike was previously unvariated, so I pieced it together from junkyard motors and mail-orders. I was building it up with a Malossi 62cc kit and a Ninja G3 pipe, revised gearing, and a CDI when I realized electric would be way more fun.

I agree with you, CVTs are great on gas mopeds. My previous Peugeots were both variated and a joy to ride.

I think Karen is still running the CVT on her Boxer ... I have to look further into this.

I'm really on the fence about adapting the Moby Variator for the electric drive. They're quite heavy and so would add a considerable amount of rotating mass to the drivetrain. I like your idea about a taper adapter - I do have a spare bottom end + crank I could try to mill down. But will it all be worth it?

I do have a lathe and a milling head, drill press, etc. available to me ... but am a bit of a noob in terms of their use!

Here are a few shots of the old powerplant:

and the spare bottom end:

Your thoughts / experience / opinions appreciated!

 

[oofnik]

Hmm, if you've already gotten rid of the variator, I suppose it would be more work to acquire a new one. It's really up to you whether or not you want to incorporate it into your design. I think that despite the added weight, it will improve your acceleration and top speed. I don't know how it would affect efficiency but I can't imagine it to be more than 5-10% lower than it would be with a direct drive, assuming the belt was tensioned properly. The Moby is quite a unique design in how it accomplishes belt tension - it shouldn't be hard to keep belt tension set with a motor drive. Just look at how all the other mopeds and scooters with variators do it. None of the other ones to my knowledge have rotating spring-loaded engine mounts!

 

[northernmike]

So. The motor has arrived! No pictures for you, yet, but it practically drops into the hole left by the AV7. It looks just like Karen's, but it's gold where hers is purple.

Also added to the kit this week: a four foot length of 4 wire #10 SJ cable, from the scrap pile at work. Thanks boss! (yes, I asked) And brake levers; Magura, matching my throttle and grip. More updates soon.

 

[northernmike]

 

[northernmike]

Hi folks. A few updates, witness:

Sorry for the blur, too much egg nog I guess!

 

[Drunkskunk]

Any new year updates?
I've been following this with intrest. I bought a Peugeot the fall with the idea that I would do the same, but then I accidentaly got it running. Now I can't bring my self to tear it appart.

 

[northernmike]

I've owned two Pug 103s, loved them both! If it's running well, enjoy it. I'm looking forward to the quiet speed this should provide.

Updates: sourcing a pair of Pelican 1450 cases (or larger) to mount as rear panniers for battery storage ... bought a 15A digital AC Delco charger for cheap, found a source for a pulley (see other post)..

And that's about it.

The bike lives 40mins north of my current address, so it's tough to work on it. Expect more progress in a few paycheques!

 

[northernmike]

Ordered H-bushing and 3 pulleys - 3.15, 3.55 and 3.95" O.D.

 

[gwhy!]

This is very a simular transmission to what they use on all the modern auto scooter and something that I think can be adapted to work very well with a electric motor weight reductions can be made to i.e the clutch can be removed. Im thinking about fitting a custom cvt setup onto a pushbike using 2 variators. Keep up the good work I will be watching this one :wink:

 

[northernmike]

Hey folks.

Progress is being made, slowly - I have all the parts ordered for my brakes and have sourced a few larger sprockets for the rear. It looks like my original gears (which I'd changed for my souped up gas motor) were going to be too tall for the HXT, so I'm reducing it a bit.

 

[northernmike]

Update: Motor mount in progress. $35 in aluminum today. Pulleys and H-bushing have arrived. Controller and Castle Link are in the post.

 

[northernmike]

Update: brakes are functional, brake light switch is on order. New headlight from France has arrived, Castle Link and a GIANT Digikey catalog. No caps, as ordered, but a giant catalog, anyway. Promising.

Have a chrome luggage rack coming thanks to eBay... Looking for a horn. Might be useful, in this crazy city.

Freewheel adapter ordered from Matt to facilitate EMF-less coasting, Castle HV 110 should be delivered already.

Man, I wish I had a shop here at the downtown apartment. Having to wait for opportune weekends to work on this is just killing me.

$$ for a123s is being saved up, but it looks like it's going to be SLAs for the interim. Oh well!

 

[northernmike]

Update in non-hub-motor-drives forum. Goodnight!

 

[northernmike]

Status:

 

[fizzit]

Wait... Why are you putting a metal can around the motor? Won't that just heat up from eddy currents and simultaneously cause the motor to overheat? Sorry if I'm missing something!

 

[northernmike]

its a etek. no metal can.

 

[fizzit]

Sorry, I was referring to this:

 

[northernmike]

Yeah, gave up on RC controllers. Not enough off-the-line ability for me. I don't think aluminum cans are a worry, though, in terms of eddy currents. Steel might pose a problem, but I doubt alu would. The eTek has much better take-off power, and compatible controllers (Alltrax 4834 etc) are easily sourced.

All I have to contend with now is affording, mounting, wiring, and charging a battery pack that can feed this bike.

 

[Jeremy Harris]

I don't think aluminum cans are a worry, though, in terms of eddy currents. Steel might pose a problem, but I doubt alu would.

That motor will cook that alloy can quickly and it will suck a load of power, too. The eddy currents in aluminium will be much higher than those in steel, which is why I'm using an alloy disc for the eddy current brake in my dyno. You need to space that tube a lot further out from the motor rotor, with a gap of at least 1/2" all around it, preferably a bit more (the magnetic field will still be around 80 to 100G at 1/2").

The problem with putting lumps of alloy close to the motor case of an outrunner has already been documented here, and that was just a bit of alloy plate with a hole in it where the motor fitted - a tube will be far worse. I fitted my first boat motor inside an alloy box, with the motor too close to one face (around 1/8" or so) and the case got very hot very quickly.

Jeremy

 

[northernmike]

Ah! What is that unit, "G", Jeremy?

Interesting stuff.

No heating problems were experienced with that setup, but I didn't run it hard. I didn't have a chance to - I smoked my Castle hV110 a few days in.

The eTek runs nice and cool, too, as I'd expect it to. The bike only weighed 90lbs from the factory with the gas engine.

Now then, has anyone got any strategies for stuffing LiPo into the hole I made in the side of the gas tank? :wink:

 

[John in CR]

The bike only weighed 90lbs from the factory with the gas engine.

I've gotta get one of these. Stronger, lower, and longer than a bike, plus it's cheaper with cheaper but better tires and brakes with plenty of room for batteries. What's not to like? Get one with registration already done and that headache is out of the way too. Availability of these kinds of vintage mopeds is going to evaporate quickly after a few more e-conversions get done.

Do any of the mopeds have a reliable multi-speed tranny in the hub, or is it just those few with a planetary gear reduction? Actually a planetary gear reduction inside the hub has the makings for a simple Retro-Direct 2 speed with the chain running in reverse driving the sun gear of the planetary reduction for low gear. Then a chain reduction running forward for 2nd. You give up being able to roll backward, but that's easy enough to get used to and overcome as long as the bike isn't too heavy.

John