crappy chinese components(specifically magneto)

[AussieSteve]

Bending a conducter changes resistance, thats how loadcells and other transducers work.

True, but not measurably in copper, with normal instruments.
I have a bit of experience with load cells.
A typical load cell is made of metal, but there isn't enough change in resistance under load to use. Thin wafers, usually 2 or 4, are attached to the sides of the bar and their resistance varies with load, (bending). I can't remember exactly what the wafer is made of, but it's not copper.
Even then, a very carefully balanced wheatstone bridge circuit and amplifier must be used to accurately measure the very minute change in R.

Other transducers commonly use a piezo-electric element.

So, (to all intents and purposes), the resistance of a wire doesn't change when it is bent.

... Steve

 

[Fabian]

I've been thinking about another electrical issue - running a small dynamo/generator from the jackshaft to charge a small 6V/12V 5-7Ah SLA battery for lights etc.
I'll let you know if I come up with anything decent. It's weeks away, but who knows?
It would only be useable with a SBP shift kit jackshaft, though, because anything else would be too hard to implement. If I do come up with anything decent, I probably should have a chat to Paul and Jim at SBP.

Steve we think alike.
I've been planning an idea to use a 2.7kw DC motor running off the chainwheel side of the jackshaft to even out the stresses once power is supplied to the DC motor.
My concept is to have the 11T jackshaft gear machined to accept an additional toothed belt or 9 speed chain sprocket and locate the motor towards the top of the A-frame where the seat post tube connects to the top tube and the down tubes.

Photo's of the motor attached.
I'd have to rig up some sort of electrical speed controller and a method of allowing the motor to reverse operate by supplying current to a 12 volt SLA battery.

http://www.hobbypartz.com/mo1602brmo.html


Fabian

 

[AussieSteve]

Do you mean an e-bike, or a hybrid?
If a hybrid, don't forget that whatever power is generated is robbed from the HT engine.
ie If you generate 1kW, it will rob a bit over 1kW of power from the HT engine.
I designed a regenerative controller a couple of years ago, but it won't drive a 2.7kW motor, only a couple of hundred watts.

I'm thinking of using a 12V, 120W DC motor, to produce about 30W, I hope.
(No-one would miss 30W of engine power.)
I started a thread on this, in the electrics section.
If enough people are interested, I'll look for commercially available motors/generators before I start, but if I'm only making a 1-off, I have a suitable motor here. (At least, I hope it will produce a usable amount of power, even at idle.)

I was thinking of running a belt from the centre of the jackshaft, to the motor/generator mounted directly below the jackshaft, then a bit of electronics, of course.

On many bikes, there's enough room under the engine, in the 'V', for a small battery.

I just checked out the pic of that motor - it's not a standard DC motor, it's brushless.
A regenerative system might be hard to accomplish.

... Steve

 

[Fabian]

I guess you could call it a hybrid system.

I intend for the piston engine and the electric motor to power the jackshaft system at the same time and also to use each on their own, but allowing the piston engine to generate electrical power, recharging the battery.

The thought of 1.5kw of petrol power (maybe more with the new Pirate Cycles stage 3 engine) and at the same time slamming in 2.7kw of electric power really appeals to me.

Fabian

 

[Fabian]

The method of location i intend to use.

 

[wildemere]

How are you going to gear the high speed (probably over 4000rpm) brushless motor to the slow speed (around 600rpm) jack shaft?

Also that motor is 36v and 60A, any thoughts on the controller and power supply setup?

 

[Fabian]

No thoughts on the technical intricacies as yet.

Step 1 will be to bolt the motor into the frame - you've got to start somewhere and once it's attached to the frame you're compelled to go forwards and complete the project.
Step 2 will be working out the mechanical drive system to the jackshaft.
Step 3 will be leaving the set up of the electrical system to a friend of mine who is an electronics engineer.

 

[AussieSteve]

2.7kW of electric would be nice, but not practical. Besides wildemere's observations, have you thought much about batteries and range? (You won't fit the battery(ies) under the motor in the 'V'.)

Speed control of the brushless motor will be another big issue. My e-bike has (had) PAS intelligent pedal-assist and even that was totally inadequate at pedalling speeds, so I eventually disabled it.
Matching HT speed to e-motor speed will be another big tripping point. (A hall-effect sensor throttle coupled to a cable throttle, or electronic (PAS-type) control, either won't be easy. As an ex- electronic designer, I'd pass this one up.)

My e-bike hub-motor is 200W and has a 36V, 10Ah batt - about 5.6A current drawn at 200W. It only has a range of 32km. (Have a look on my profile page album to see the size of that battery, then transpose up to your requirements. Possibly a small trailer full of Lithium batteries.)
Imagine the size of battery you'll need to get any range with a 36V, 60A, 2.7kW motor, even used in conjunction with the 2-stroke.

(Sorry to rain on your parade. As I said, it would be nice to have a 2.7kW electric, but.....)

... Steve

 

[Fabian]

I never said i intend to use the electric motor at 100% duty cycle.

The electric motor is more intended as a charging system to top up the batteries (to be housed in the trailer) and for powering an automotive lighting system.

My intention is to run the piston engine at 100% duty cycle.
When going downhill, i'll hold full throttle and let the system generate power.
When riding on the flat, i'll use the piston engine on it's own and when going uphill, the electric motor supplies additional "burst power".

Fabian

 

[AussieSteve]

The biggest problem there is that you'll still need a battery big enough to supply up to 60A current. That's a small car battery in lead-acid or a big bank of Lithium cells. 60A is one **** of a lot of current. Your wires would need to be almost as thick as those going to a car battery.
Then there's the brushless controller...
(Duty-cycle on an electric motor is slightly different and will vary depending on speed, as well as the 'duty cycle' you speak of, ie how long the motor is used for. If you're giving it a bit then you will draw 60A.)

I'm honestly not trying to upset you or start an argument, but it really isn't practical on an MB.

The censorship is over the top, I only said h e l l.

... Steve