HT Motor + Shift Kit + 6V/12V generator

Discussion in 'Electrical' started by AussieSteve, Feb 18, 2010.

  1. AussieSteve

    AussieSteve Active Member

    I'm thinking about putting together a generator/dynamo charge system for 6V/12V 5-7Ah batteries to run from a shift-kit jackshaft via belt-drive.
    The generator is only about 1 1/4" diameter and 2 1/2" long - not too intrusive if they work OK.

    If the generator that I have in mind does the job properly, there should be about 30-50 Watts of continuous power available, or more for intermittent use, at 6-12V.

    I will also build a regulator to suit.

    I'm wondering if there'd be enough interest to make more than one, just for myself.
    If practical, I'll make them for sale, but wanted to do this little bit of 'market research' first.

    I've been thinking about this for quite a while but have been busy on the main parts of the build. That's almost done.

    ... Steve

  2. AussieSteve

    AussieSteve Active Member

    No replies, so I'm only making a 1-off for myself, it looks like.
    I just posted all of this in another related thread instead of here, so I copied it and pasted here where it should be.

    I got as far as working out how to mount the motor, (hereafter called a generator), probably just above the jackshaft, it fits like a glove and the approximate gearing to start with, about 8:1 or 10:1. That's just doable in the space. (At 10:1, the generator will be spinning at 1.4 times the speed of the motor. Might be too fast yet. At 7000 engine rpm, the genny will be spinning at 9800RPM. Trial and error will get things right.)
    Incidentally, this method has one drawback - it will only generate when the bike is moving. ie The clutch must be engaged to turn the jackshaft, so the battery must carry the lights while the bike is stationary.
    Not much of a problem. This type of system needs a battery to function well, otherwise everything stops working when the engine stalls or the lights dim when the idle is low and there'd be something wrong if the battery couldn't run the lights for a short time without generator input.
    ie A 12V 7Ah battery could run a 60W headlight for an hour or more. (Not that we need 60W of light.)

    The generator is small but gutsy, as a motor it uses about 120W under load, (10A @ 12V). It came from a 12V portable compressor for pumping up car tyres.
    It's 57mm x 36mm, with a 3mm shaft that has a flat spot for a grub-screw.
    Should go close to doing the job.
    For now, at least, I'm setting up with plastic pulleys and a belt, but I'll have to get metal pulleys if it works OK. I'll probably mount the drive pulley on the side of the 17T sprocket, or hard up against it.

    I haven't thought about the regulator yet, but that bit will be easy. I want to ensure that I can get usable power first.

    Pic of the motor below.

    ... Steve

    Last edited: Feb 23, 2010
  3. HseLoMein

    HseLoMein Member

    im thinking of doing something similar. My buddy and i are designing a regulator and battery charger, with the logic for a full lighting setup, all LED using a total of 2 amps of power @ 6v, 12v would work too. The generator attached to the jackshaft is a great idea. If you can get it working and geared right i would be a poenetial customer.
  4. AussieSteve

    AussieSteve Active Member

    Hi HseLoMein.
    There's no reason why it wouldn't work, once the right generator and gearing are found. Hopefully, the current motor will do the job. They're cheap, readily available and fairly high power for their size.

    Now, to my specialty, electronic design. Sounds like you might know what you're doing there, too.
    The first bit is mechanics and 'trial and error' to get enough usable power. The voltage is irrelevant, that can easily be converted with a buck/boost style switching regulator.
    I've still got tons of spare parts left from my old business, (I no longer work), that would be perfect for the regulator. ie Very low Rds [on] MOSFETS, of the order of 5-10milliohms 'on', several types of DC-DC converter IC, heaps of cores, winding wire and a coil-winding machine. No trouble making a regulator/charger to suit the system.
    I've also got Circuit Simulation software, PCB design software, blank pre-sensitized S.S PCB material, etc etc. My specialty was really microcontrollers, and I still have heaps of those, (PIC 12C508, 16C711, 16F84A, 16F876), along with a compiler and programmer, so I could make it a 'smart' system if necessary.

    I'll keep everyone posted on how this develops.

    ... Steve
    Last edited: Feb 24, 2010
  5. HseLoMein

    HseLoMein Member

    I need to hop in the first flight the AUS, you sound like you have the perfect workshop. my next project will be trying to wind a more powerful coil. I think i can get more than 10 watts out of the extra coil i have installed. I just dont feel like winding and counting by hand. and i dont have a real good understadning on winding a coil. know of any resources?
  6. AussieSteve

    AussieSteve Active Member

    Resources? I've got lots of books here. When do you arrive?

    Best I can say regarding resources is to do a good web search. It's pretty complicated.
    I mostly work with high-frequency coils, using (powdered iron or ferrite) cores that I have all of the specs on, especially relative inductance and core saturation figures etc.
    First, it's not too hard to work out the number of turns and wire gauge to be used, along with any fancy winding such as double-spacing etc, depending on voltage and current, then the core is chosen to suit.

    You're sort of working the other way here - make a core, see how many turns you can fit on it, then cross your fingers as you measure the output.

    I had a go at an extra coil under the magneto cover, opposite the original coil, but it didn't show enough promise to be worth continuing, hence the latest effort.
    I know that this will work.

    The problem with the extra coil is that only the windings are near the magnet, rather than a section of closely-spaced core. That reduce's the coils efficiency dramatically.
    If you can make a core the right shape and size, there's not enough room left for a decent number of turns on the coil without going down to too thin a wire for the job.
    I had a final attempt with 0.2mm enamelled copper wire, as many turns as I could possibly fit. The voltage came up nicely, but the series resistance was too high under even a moderate load.

    The coil I mentioned will be an integral part of the regulator, switched at 20kHz+, for step-up/down to 12V. (Actually, a miniature high-frequency transformer, about 1" x 1", but I'm lazy and call them all coils.)

    ... Steve
    Last edited: Feb 23, 2010
  7. Scotchmo

    Scotchmo Member

    A couple of issues: It will only charge when moving and you will have to gear it way up since it is running off a reduced output speed from the gears. It might work but you would be better off adding a pulley to the crank or driving it directly off the crank.
  8. AussieSteve

    AussieSteve Active Member

    Of course it will work.
    I covered both of the issues you mentioned, earlier, in post #2.
    (The crankshaft to jackshaft ratio is only 6.97:1, not hard to overcome.)
    And where exactly do I fit the generator if I run it off the crankshaft? Of course it would be better, but it's not practicable.

    ... Steve
    Last edited: Feb 23, 2010
  9. Scotchmo

    Scotchmo Member

    You are right. I did not read your second post. You were already aware of those problems.
  10. AussieSteve

    AussieSteve Active Member

    No worries, Scotchmo.
    As I said, of course it will work, that's a given.
    What I don't know is just how well it will work and how long the motor/brushes will last at those rpm. I might have to gear it a little lower, but then it might not provide much current at lower revs.
    All trial and error. And fun.

    ... Steve
  11. AussieSteve

    AussieSteve Active Member

    I just spent half the afternoon searching (eBay) for potential belts and pulleys.
    Maybe I was using the wrong search terms or something, but found nothing suitable.
    I think that a v-belt would be best, but I'm open to suggestions.
    Also, the pulley on the generator would be best if it was metal.
    I considered a small timing belt and pulleys, but I'm not sure if that type would stay on at the speed.
    Can anyone point me in the direction of a supplier of this sort of stuff?
    For the generator end, I'm after a couple of pulleys, in a couple of sizes about 10mm to 15mm diameter to suit a 3.175mm, (1/8"), shaft.
    For the jackshaft, a couple of pulleys from about 80mm to 120mm diameter would be good.

    Any help appreciated,

    ... Steve
    Last edited: Feb 24, 2010
  12. Fabian

    Fabian Well-Known Member

    Hi Steve

    Have you considered toothed belts out of 1/8 scale R/C cars.
    Those things are very strong and just don't seem to stretch.

  13. AussieSteve

    AussieSteve Active Member

    That's the sort of thing I've been looking at. Those actual belts and pulleys aren't suitable, the belts are too short and the pulleys don't come in the right sizes. eg. I need a 100mm to 120mm pulley for the jackshaft.
    As spare parts for RC cars, they're sold mostly by part number and not by length, pitch, etc.
    I'm not sure if timing belts will work well at high rpm, either.
    I found a place called MiniBearingsAustralia last night. They have a great range of belts and small pulleys, both notched and timing styles, but none in 100mm+.
    I was thinking v-belts, but most that I've seen won't go around a really small ~10mm pulley.

    The search continues.

    ... Steve
  14. gothicguy64

    gothicguy64 Member


    have you tried a modelshop like as model planes cars ?
    hi buddy i think its a great idea im watching with great intrest
    ohhh as for my built num 2 ,,,,i found a frame mtx1 cell i have the wheel an rotor of num 1.
    the exhaust i ran orig was a stock drilled an cut by tony
    i got poo poo off goege an it mades 2x bottom an mid but looses 10 at top
    i ould blast off after 2 pedals and leave cars standing for 40khp was funny
    i intend to add the jackshaft as well
    if not i,ll run a 36 tooth rear
  15. AussieSteve

    AussieSteve Active Member

    Howdy, Brad.
    There aren't any model shops that I'm aware of in this area, within riding distance.
    I've checked out a couple of online shops but they didn't have much.
    I'll have another look at MiniBearingsAustralia later. I might be able to get the generator pulley and belt from them, then just find another supplier for the jackshaft pulley.
    I've got to bottle a batch of my home brew now, but later when I get time I'll continue the search.

    With the jackshaft, you'll be able to leave the cars behind to 50kph. Much safer, you can sit in the traffic stream on 50kph roads - much safer than riding in the gutter.
    It's great being able to idle along at walking pace in 1st, too.

    ... Steve
  16. wildemere

    wildemere Member

    "Razor" scooter wheels are urethane and are 100mm, the center hole is 20mm, you could friction drive the generater from this wheel using a rubber roller on the generator. Or machine a groove in it and use the band and drive pin from an old upright Hoover or similar appliance.

    Have you thought about friction driving it from the back wheel? On a spring loaded mount? Like a bottle dynamo mounted sideways.
  17. AussieSteve

    AussieSteve Active Member

    - I realised that I can't go above 80mm for the jackshaft pulley. Also a scooter wheel is too wide for the space and very hard to attach properly to the jackshaft.
    - A belt drive is better for the setup I'm planning - I wouldn't even consider a friction drive - harder to set up and more problems.
    - No I haven't considered running a home-made bottle-type dynamo friction-driven off the rear wheel. I can buy one of those ready made.

    I'll need a bit better belt than an old hoover one - this will be spinning the generator over at up to 10,000rpm and have a fair bit of load on it at times.
    I'm looking at modern reinforced belts. I'm leaning toward timing belts more, now, because v-belts don't run well around extra-small pulleys.
    Since only an 80mm pulley fits the jackshaft well, the generator pulley needs to be ~8mm+.

    No offense, but I've worked out my design and didn't ask for help there, only if anyone knew of suppliers of belts and a range of pulleys.
    I'll need to buy a few sizes to dial in the gearing. I'm still working my way through MiniBearingsAustralia, a slow, hard-to-navigate site, but I'm starting to find what I'm looking for. If I can find them, I'll get an 80mm for the jackshaft and an 8mm, 10mm, 12mm and 14mm for the motor. That should get me in the ballpark.

    At MBA:-
    Found a suitable 10mm timing pulley - $18
    Also probably need at least 12mm and 14mm for testing - $42
    And an 80mm pulley, (this will need boring to suit the jackshaft). - $34
    A timing belt to suit - $10

    It's hard to spend that much on the belt & pulleys, but use a cheap $10 motor.
    By the time I get a quality motor and the above, this will cost me an arm and a leg.
    (Still needs the battery and electronics on top of that.)

    Unless a reasonably-priced belt and pulleys turn up, I'm done with this.
    I've spent over 12 hours now, just looking for them.

    ... Steve
    Last edited: Feb 25, 2010
  18. AussieSteve

    AussieSteve Active Member

    Since the pulleys will be so expensive, I've decided to do this properly and fully test the motor for output first, then I only need to buy (the correct) 2 pulleys and one belt.

    Did my first tests and they're fairly promising, power-wise, but I have no idea of rpm, so I just stretched the budget and bought a digital optical tacho. (A good toy to have around for other stuff.)
    I've been running the generator pretty slowly for testing so far.
    Measurements indicate that if I can run the generator at 4 times today's test speed, I'll get 49W at 12V. Just need to know how fast I'm running it before I up the speed too much.

    Still after cheaper pulleys.
    (Maybe I should just go the whole hog, use a bigger motor and small chain and sprockets then make a starter-motor/generator like on some ride-on mowers?)

    The saga continues.

    ... Steve
    Last edited: Feb 25, 2010
  19. has lots of different pulleys and belts. They do alot of custom stuff as well.
  20. AussieSteve

    AussieSteve Active Member

    Thanks, breaksalltherules, I just checked out McMaster-Carr.
    A much easier site to navigate, but similar prices.
    ie. $39US for the jackshaft pulley, $9US for the generator pulley.
    Great range of stuff, though.

    At this point, it looks like I'll probably be buying the ones from MiniBearingsAustralia.
    First, a new multimeter, it seems, before I can do much more. It died of old age last night.
    Gotta wait for the tacho anyway, so I'll put things on hold until then.

    ... Steve