Automobile starter motor to power bicycle?

[DerStrom8]

Good day, everyone

I am in need of a somewhat large DC motor, as I plan to motorize my bicycle. I am having some trouble, though, finding a motor that would work. I was wondering if you guys think an automobile starter motor would work for this? I know they are intended to run no more than 15 seconds at a time, but I don't imagine running it for 2-3 minutes at a time would cause too much damage. Then again, I could be wrong--the motor could heat up and burn out after 30 seconds or less. For this reason, I wanted to ask for some opinions. Do you guys think that a starter motor can put up with this kind of strain? If not, can you suggest any other motors that would work? This is a low-budget project, so if I can find motors in used equipment, it would be preferable.

Thank you very much for the help!
Regards,
Der Strom

 

[crutschow]

It could perhaps work if you used PWM to control the speed and limit the power. But starter motors are brush-type with simple bearings that are not designed for long operation so you could possibly have to replace them frequently. They also are series type, which are not particularly efficient so your battery life would not be good.

You would likely get much better results with a small, efficient, permanent magnet DC motor such as those used in small electric scooters.

 

[Diver300]

I think that you would find that starter motors are not easy to control.

30 years ago I would have said that a car dynamo would be a far better motor, but cars all have alternators so dynamos are nowhere to be found.

One of the other motors from a car, such as the cooling fan or power steering motor would probably be far better.

 

[DerStrom8]

One of the other motors from a car, such as the cooling fan or power steering motor would probably be far better.

I had thought of that, but I didn't think they could provide enough horsepower. I figured (with a bit of help ) that I would need about .4HP for this project.

 

[SABorn]

Do a ebay search as i know China makes PM motors for use with push bikes,like a flatish pancake style and dont think they are that dear, also the weight is much less and the efficiency would be far better. MPA (miles/amp)

 

[Jaguarjoe]

About half way down there is a chart listing 12 different electrobikes including performance, motor power and battery type:

https://en.wikipedia.org/wiki/Electric_motorcycles_and_scooters

The Velosolux has a 49cc gas engine that provides 0.8 hp

 

[Mr RB]

Check this supplier for tons of motors, prices are not too bad;
**broken link removed**
they sell motor drivers too.

Or check ebay for "electric bicycle motor" as there are a lot of Chinese motor suppliers sell motors there too.

 

[carbonzit]

I was going to say that I couldn't believe nobody had mentioned All Electronics yet in this thread. I have one of their catalogs here next to me, and it has lots of scooter motors in it, cheap, plus the other stuff you need (gears, chains, wheels, power controllers, etc.)

However, checking their web site, all they seem to have now is a single 24-volt, 250 watt motor. They must have gotten rid of all their other good stuff.

 

[kinarfi]

I would recommend checking with **broken link removed** and use a PMW to control the speed

 

[tcmtech]

Check with your local scrap yard and get a DC generator off of a piece of old farm machinery or similar type of older equipment thats been scrapped. Odds are you will get a good workable DC generator that you can set up as a high torque low RPM DC motor for less than $5 - $10.

You might even find one of the later model ones higher amp ones with the built in cooling fan and blow through cooling design setup too!

 

[DerStrom8]

Okay, after doing some more research I have organized my main ideas for this project. The update is as follows:

I plan to use either a pre-1980's automobile starter motor or an automotive/farm tractor DC generator (dynamo), connected to a set of heavy-duty batteries (not sure of the type yet--I guess whatever I can find) via PWM circuitry for the throttle. The bicycle will be chain-driven, with a sprocket connected to the motor shaft and one connected to the rear bicycle wheel. Because of the way the bike is designed, it will not be possible to run the chain from the motor to an existing sprocket, as it would turn the pedals and could cause an injury. Instead, I will be welding a sprocket to a sort of "flange" (not the right word, but you get the idea ) on the rear wheel. This way, the "freewheel" mechanism will allow the wheel to turn freely when the motor is switched on. To avoid a motor stall (and therefore, excessive current draw), I plan to pedal up to speed before turning on the motor (depending on the torque of the motor). This would only work, of course, if I matched the speeds perfectly--otherwise it would put intense strain on the rear wheel or the motor chain as the speeds begin to equalize. This is a part for which I could use some more suggestions.
I also hope to set up some sort of regenerative braking system to recharge the batteries. I hope to be able to use the motor for the regenerative brake generator, if possible. I had originally hoped to have a switch on the handlebars to select between "Drive" and "Charge", and charge the batteries by pedaling, but I was told the losses would be too high. That is why I decided on using a regenerative braking system, but I need more information.

That is the main idea thus far. I will post more updates as I get more suggestions.
Thank you all very much!
Der Strom

 

[HommerSimpson]

Old VW's had DC generators.. Most get removed and upgraded. And Chry Starters have built in Gear Reduction.
Food for thought when looking for parts. < that almost rhymes

 

[DerStrom8]

Old VW's had DC generators.. Most get removed and upgraded. And Chry Starters have built in Gear Reduction.

I have various Volkswagens around, mainly '70s beetles, but all of the parts are being used for something. I was going to use a starter motor from a super beetle, but I realized I had let a friend of mine use it for a rat rod he was building. I am still keeping my eyes out for a generator or starter motor, though. Thanks for the suggestions!

 

[Mr RB]

I think you will pay a lot more for a old generator from a vehicle wreckers (as they know what they cost!) than you will for a new electric bicycle motor from China or Ebay. The new motor will also be lighter and of a more efficient shape and better torque/RPM curve (large diameter rotor etc).

Starter motors are a bad choice for electrin bikes as they have poor energy efficiency and simple bronze bush bearings etc and are meant for very short intermittant time use at very high torques.

Regenerative braking requires fixed gearing (removing the freewheel ratchet) and most people agree it gives worse energy economy on a bicycle than freewheeling as much of the time on a bike you can freewheel along a flat or down slight slopes. Regen braking in a bike can also be dangerous as it has a high likelyhood of locking up the back wheel.

 

[HommerSimpson]

you dont want to use a starter motor off a VW unless its off an AUTOMATIC.. the end of the shaft on STD shift starters on vws is supported in the bellhousing. So you would have to build a support for it.

 

[DerStrom8]

Hello

I think you will pay a lot more for a old generator from a vehicle wreckers (as they know what they cost!) than you will for a new electric bicycle motor from China or Ebay. The new motor will also be lighter and of a more efficient shape and better torque/RPM curve (large diameter rotor etc).

The point of this project is to motorize a bicycle cheaply with readily-available parts, that can easily be scrounged up for little cost. My goal is to not have to buy anything online; If someone has the right skills and connections, it should be easy to find a generator for quite cheap

Starter motors are a bad choice for electrin bikes as they have poor energy efficiency and simple bronze bush bearings etc and are meant for very short intermittant time use at very high torques.

My hope was that a starter motor would work for slightly longer intermittent times at a lower torque (achieved by the gearing, or in this case, 'sprocketing'). I have heard of starter motors being used for small racecars and go-carts, and there hasn't been a problem.

Regenerative braking requires fixed gearing (removing the freewheel ratchet) and most people agree it gives worse energy economy on a bicycle than freewheeling as much of the time on a bike you can freewheel along a flat or down slight slopes. Regen braking in a bike can also be dangerous as it has a high likelyhood of locking up the back wheel.

If this is true, do you have other suggestions of how I can use the momentum of the bicycle to recharge the batteries?

you dont want to use a starter motor off a VW unless its off an AUTOMATIC.. the end of the shaft on STD shift starters on vws is supported in the bellhousing. So you would have to build a support for it.

I think that if I can get a hold of a motor, I will find a way to mount it, no matter what. Even if it is only possible to mount it the way you suggested, It wouldn't be too much work to build the support.

 

[ronv]

If you think about it the generator is a much better choice. They are made to run for 1000's of hours while the starter need only be designed for a 100 or so. The pwm for the starter will need to be bigger, but of course you get a several of horsepower out of it. Enough for super wheelies. The generator is more in line with your power requirements.
If you pick an rc time constant of a couple of seconds on the ramp up of speed it will save you on the jerky starts and be easier on the pwm. You want the ramp down to be fast of course.
PS.
I think starters are series wound so it will be harder to control.

 

[shortbus=]

Starter/generators were common on lawn tractors.
**broken link removed**
https://www.tpub.com/content/recoveryvehicles/TM-5-4240-501-14P/css/TM-5-4240-501-14P_200.htm

 

[Rando]

How about a motor from an electric wheelchair?

 

[SABorn]

Most of the motors used on retrofit bikes are a 3 phase PM motor for high torque and efficiency, not to point out the weight saving.

With a hungry auto starter motor the weight is high, then you will need a couple of car batteries to give a reasonable run time, dont know about you, but be buggered if i would want that weight on my bike.

China makes the 3 phase bike motors by the 1000s and also the speed controllers, a lot come with the litiumn battery too for extra weight savings.

It makes me giggle to think of some clunky old starter motor and a big auto battery on a push bike, gee i would be tired getting the bike out the shed.