Large 12 Volt Motors?

[Bruce]

Hello,

I'm interested in building a Bonneville Salt Flats Bar Stool Racer. Since they are limited to 12 volts, I'm wondering what the most powerful motor might be?

At first I thought that a large truck starter motor would be perfect, but the biggest starter motors I could find were only about 5" in diameter.

Are there 12 volt motors larger than that available?

What are they used for and can anyone tell me where might I be able to find one?

Thank you!

Bruce

[speeddemon0308]

this is an idea to try to try to get some killer speed... my freind tryed on his race mower.. with sucsess.

get a one way bearing ( like what come on bikes.. the way they freewheel when you dont pedal ) and hook that up to motor #1.. so have that geard to get you to say.. 50-75 or so.. and since its hooked to motor #1 when motor #1 tops out.. you have motor #2 geard much higher to get you to say..100-150 or what you want and when your turn #2 on it will start to move faster and then #1 will start to free-wheel so that you can either shut it down.. or just turn it down to save some battery power!!!!

[Bruce]

Thanks for the clever idea of using multiple motors with a freewheeling clutch to gain more speed. I'm sure this would work fine, but unfortunately the Salt Flats rules,

http://www.saltflats.com/barstool.html

specify: "limited to ONE single 12 volt motor".

So what I am looking for is a 12 volt motor that is bigger than a truck starter motor. Preferably 7 inches or larger in diameter.

24 volt motors are quite common, but big 12 volt ones seem to be quite rare. Perhaps something from a sweeper / scrubber or other industrial DC motor application? Do forklifts ever use 12 volt motors?

[speeddemon0308]

run it to a jack shaft and used some cent. clutches!?

one motor!!

[Bruce]

A jackshaft and two centrifugal clutches could certainly work with one motor. But they have another rule...

"No Gearbox, or Mechanical Shifting Device."

I think this would be considered a shifting device.

The gassers have a saying that's something like, "There's no substitute for cubic inches". To which I'd have to agree. A bigger motor should allow for higher top speed, all other things being equal.

So where do we find 12 volt motors bigger than starters?

[Terry Skinner]

So where do we find 12 volt motors bigger than starters?

they have some pretty big starters on diesel trucks. Also you might try a 6v starter with a 12 volt battery. Shorten the life but up the HP. More than once I have put 12v to an old Ford to get the engine to turn over fast enough to start..........Terrt

[Frank McGrath]

I am working on an electric stool, but I am using a 24 volt fork lift motor. Are there any rules about using variable speed controlers at b-ville? If you can, I have a control panel with contactors that came from a 12 volt unit. And yes, there are 12 volt electric lifts on the market. Mostly pallet jacks. Check with your local fork lift dealer. they may have a derelict laying around somewhere. Call and ask for the rental dept or the shop foreman.

[Thunderbolt51]

contact D & D and ask about a motor/controller/battery BEST suited for your application. Battery and controller selection IS as important as PROPER motor selection, it all needs to work together as a combination to be succesful, keep in mind that BIG/LARGE in electric usually means HEAVY and heavy means SLOW. Do the research first, there's a lot to learn the peculiarities of battery and electric motor systems. Some EV suppliers are eager to help with info. There are also EV forums with a wealth of knowledge from members.

http://www.ddmotorsystems.com/
http://evparts.com
http://cloudelectric.com/

http://tech.groups.yahoo.com/group/ev/

http://www.saltflats.com/barstool.html

[Bruce]

Big (http://barflyracers.com/showthread.php?p=11212#post11212) starters from diesel trucks end up not being as big as one might expect. Though they still may be the best option. One company that makes heavy equipment starter motors is Prestolite. They were the only company I could find that quoted specifications such as size and power for their 12 volt starter motors. I found some good information on these 2 pages:

http://snipurl.com/1txa8

http://snipurl.com/1txa9

Their MS2 series starter motor is 5.118" diameter, 56 lbs, 12 volts, 7.5KW and is suitable for starting motors up to 915 cu in. Their MS9 series is the same diameter, 12 volts but more powerful at 8.2KW.

8.2KW comes out to about 700 Amps or 11HP. My (admittedly crude) calculations indicate that more power than this is needed to overcome the wind drag of a bar stool at 60MPH.

Of course, like using a 6-volt motor on 12 volts, you could just rewind the motor with thicker wire for more power. But now you will be facing overheating problems such as burnt insulation / shorted windings and melted brush holders, etc. The solution would be to start with a bigger motor which could dissapate and withstand the heat better.

As far as I know, there are no rules that prohibit using electronic speed controllers on B-ville racing bar stools. It would seem that a speed controller would be almost a necessity to keep the tires from spinning when getting up to speed, if you had enough power to go 60MPH. This bar stool has a speed controller:

http://snipurl.com/1txac

So, I wonder how big a 12 volt motor from a pallet jack is? Larger than the Prestolite's 5.2" in diameter?

Using a 24 (or higher) volt motor with 12 volts is going to result in it running slower than it would at higher voltages. You could increase your gear ratio to compensate, but you will reach the current limits of the motor before you get the full power out of it.

I checked those links to EV suppliers. Lots of interesting parts there for sure. Few 12 volt motors though. One was this one:

http://cloudelectric.com/inc/sdetail/608

I liked it since it was a series wound motor. But it was only rated for 95 Amps on 12 volts. The ideal motor would be capable of drawing 2,000 Amps (24KW or 32HP).

Another interesting 12 volt motor,

http://snipurl.com/1txad

was this 5KW Lemco. But being a permanent magnet design, I'd be wary of giving it too much current for fear of damaging the relatively fragile magnets. Big powerful motors use wound fields, not permanent magnets. And at a whopping $1,650 the Lemco didn't seem like a good value either...

I'm not too worried about the motor weight. I'd rather have a 100 lb 30HP motor than a 50 lb 15HP motor as I believe the larger power is necessary to overcome the aerodynamic drag at speed. Increased weight is not as large a penalty in land speed racing as it is in other kinds of racing. And if the barstool weighs 200 lbs instead of 150 lbs, that's only a 14% increase in total weight including a 200 lb driver.

[NED FRY]

Bruce -- how did you ever turn out on your project ?

[Bruce]

Thanks for asking Ned. Unfortunately my Bonneville Salt Flats Bar Stool Racer project is on indefinite hold. I am still quite interested in it though. Hopefully some of the research that I have done can help others. Here's what I have come up with so far:

Large 12 Volt motors are not that easy to find. The ones in pallet jacks and small lift trucks are too small. Maybe there are bigger ones out there, but it seems like the most powerful stock units are heavy equipment starter motors. You could certainly rewind any motor with thicker gauge windings so it would give high power on 12 Volts, but as I understand it, the limiting factor is the area of the brush to commutator contact surface. That area is directly proportional to the amount of current that can be drawn without excessive arcing. Motors that are built for high current have large diameter commutators for more area. The commutator on some high current / low voltage motors is even larger in diameter than the armature.

Here's a recap of my research:

Bruce's Barstool Racer Research on Motors, Controllers and Batteries

Controllers:
Two 12 volt high current controllers are commonly available, the Curtis 1205-3XX rated
at 400A maximum current and the Altrax 2444 which is also rated at 400A maximum.
These controllers can be modified to output 1,000A max.
A controller is nice to have as it allows for slow speed use when not racing.
It also makes getting up to speed easier as you can accellerate smoothly up to the
top speed of the controller and then engage the bypass contactor to directly connect
the battery to the motor.

Motors:
Leece-Neville 12 volt starter motors:
MS2 series - 5.1" diameter, 56 lbs, 7.5KW
MS9 series - 5.1" diameter, 8.2KW

Delco Remy 12 volt starter motors:
40MT - 5" case diameter
42MT - 5-1/2" case diameter, 7-3/8" long - 7.76KW, 10.4HP, 1,650 Amps, 58 lbs
50MT - 5-1/2" case diameter, 10-1/4" long, 8.5KW, 11.35HP, 2,000 Amps, 75 lbs
The DelcoRemy 50MT motor is a common large starter motor, used in locomotives and
heavy construction equipment like earthmovers. It has 6 field windings vs the 40MT and 42MT which have 4. But the 42MT may be a better choice unless the battery can reliably produce 2,000 Amps.

Batteries:
Optima Yellow Top Group 31 - The largest Optima. Reasonably good current output
but it would be better if it was bigger.
Eagle Picher Horizon 12D2000 - 57.6 lbs, rated at 2400+ Amps for 5 Seconds @ 80F
to 10.7 Volts. Better current output than the Optima. At 30 inches long, it
may not fit under a barstool easily, however.
Eagle Picher also has the 12A5000 battery that may be good.
Trojan 8D-AGM - 155 lbs. Shorter than the Horizon batteries, but the current output
probably is not as good.
The Horizon 12D2000 is a common large truck starting battery and is probably the best
choice if it can be fit into the vehicle.

I hope this helps. Please feel free to add any corrections or let me know if you think I'm on the wrong track.

All the Best!

Bruce

[NED FRY]

Hi- Bruce-- I have been busy running a sprint car--- but have the Bonneville Project up on 4 wheels and air package installed-- It looks alot like a pointy Indy car-- except for the bar stool way up in the air ---LOL----I'm ready now for the starter motor--What tooth gear would you put on motor-- and what on axle--- I did not plan on running controller.---- I don't think Cec McCray ran one.

[ckoczara]

Bruce -- how did you ever turn out on your project ?

I race R/C cars with my sons, and they use Lipo batteries. Very expensive, but the difference is night and day on these motors. Is this a possibility for you? I'm not sure where you might find a unit, but the weight advantage may be advantagious to your salt flat run. Just a thought.

Chris K.