Starter moter

i am lookin at using a carstarter moter for my bot because i have a low budgit and can get one at a scrap yard for a couple of bucks i was wondering if they can go in reverse if the curent is reversed i know that i have to cut the field winding coil wires and conect them directly to a battery and take out the selanoid but if i reverse the curent after that will the motor reverse or is there some kind of mecanical catch to stop it from reversing
and dose the selanoid move the gear on the motor or the whole insides of the motor and the shaft that comes out how long do they last do they burn out after a certan amout of time or do they last a while can you give me rough specs of a starter motor like hp torke and rpm

I only have seven words for you!

http://homepages.which.net/~paul.hills/index.html

If youre strapped for cash, and still want to build a robot, then startermotors arent realy the way to go.
For the same amount of money you can get some wipermotors. With 4 or 6 you can get a heavyweight moving, giving more controle and upgrade possibilities in the future.It wont be fast, but you can use smaller cheaper batteries and due the low speed On/off relay control can be used.
And speedcontroling startermotors was a disaster, as my first robot used a startermotor, so I speak from experience.It isnt cheaper.

my new (well, havent actaully started it yet but got the bits sitting on the table) featherweight uses a starter motor.

wont say any more than its name.....

Trauma.

Or you could call it Fireball :)

I can almost smell the Nicads burning already.

:)
who said it had NiCads????

yeah ok, it does :sad:

go away..... snot fair.... blub.

(being serious though, Im not daft, Id thought of the current requirements.)

Starter Motor 4kG, battereis to run it for 5 min 2kG, over half the weight gone, doesnt leave much left for anything else.

When we got the Litton Motors they were £35 each. Pitty the CIM2s are more but they are better built. Starter Motors can work but are very unreliable and this is probably why hardly any are used. To use them you really need a current limit.

In all fairness, i do not recommend starter moters in a robot, not for drive at least. Not because they are unreliable because the ones ive used in 2 robots were very reliable and powerfull, but simply because there too hungry for amps, and speedcontrol is virtually out of the question.

We had a 40Ah SLA battery on board, 2 startermotors for drive, and we could barely make it last the 5 mins in a fight. We had heaps of power though, and loads of torque.

--
Leo

thanks for all the help so they draw a heap of power you said like how many amps and i still didnt ancer my question about reverse or if the selanoid moves the gear or he whole shaft of the motor thans for the help how fast do you think it would go on 20 amps

mine drew well over 180 amps during acceleration, and about 100 during driving.

Perhaps these will answer some of your Qs Davd..

http://www.m.case.btinternet.co.uk/html/stater_motor_mods.htmlhttp://www.m.case.btinternet.co.uk/h...otor_mods.html
http://www.mgcars.org.uk/electrical/start_sol.htmlhttp://www.mgcars.org.uk/electrical/start_sol.html
http://www.mgcars.org.uk/electrical/start_motor.htmlhttp://www.mgcars.org.uk/electrical/start_motor.html

if you limited the curent i could get how low do you think you colld get the curent and still get a reasionabel amout of power and dose the selanoid move the gear on the shaft or the whole shaft

Forget limiting a startermotor, you will rob the only advantage those have. Torque for amps.
And only 1 brand of relay I know and trust,useable in RW and capable to switch startermotors or bigger on A. Albright. At least a SW 80B .Or when you want reversing, the SW 88B.

On the later pre-engaged type it moves the gear on the shaft.

If you would have read the link that I posted above, it would have answered all your questions!

But please, learn how to spell properly. Your posts are really difficult to read.

people assume there is only one type of starter motor on the planet. 4kg??? nope.

In case our friend hasnt read the links above, basically, you have to open the motor, disconnect almost everything, all armature brush wires and the feild coil wires, then take them all outside of the motor. Then you have the wonderful job of wiring them, which is a little tricky, especially at 3am when rushing for an event.

I havent bothered. It runs one way only, as the motors Ive rewired in the past havent been that great as drive motors. If you are considering them, Id say for weapons only. just a personal view though.

Is this still true for permanent magnet starter motors? I would have thought these would run in either direction without modification.

You still have to isolate the motor case from the chassis, though.

true, there was me thinking there was only one type of starter motor on the planet too.

never used one myself, but yep, theres lots of ways and means.

Current limiting any motor will always reduce the power it can deliver if it hits that limit. It does however conserve batter power and prevent damage to the motor and controller. The problem is most starter motors have very low resistance and when starting act like a short circuit. Without a really good current limit (for PWM controllers it needs cycle-by-cycle limiting for best performace) it will damage the MOSFETS over time. We only use 4.8Ah for our two 800W motors with a 70A limit and we have never run out of power in a 5 minute fight.

There are of course more than one type of start motor. But in general the ones Ive seen are usually alot heavier than other motors for the same power output and require big batteries. James, looking at your other robots if you say it will work then Im sure it will and I look forward to seeing it in action.

i did read the link it told me a lot but it did not ancer the question about the gear sliding on the shaft or the whole shaft sliding and limiting the curent is out of the question im tying to build on a very low budgit so is there any other motors that will work that i can pickup at a scrap yard thaks for the help one of you said wiper motors are good and you can wiper motors at a scrap yard to right thanks for the help

wiper motors are best for featherweights. if your looking at bulding a heavy, then wheelchair motors would be the easiest to get hold of on a scrapyard (we got ours from there). they may also have the control gear as well, which can be easily modified.

Theres a special chapter on that page called http://homepages.which.net/~paul.hil.../Starters.html

I used starter motors for the drive power in Velocirippa for 2 years and actually qualified for series 3&4
with them. They had tremendous torque at only 12v but the current draw was horrendous. In combat I
would often find cables stripped of insulation or even melted together, and lots of puddles of solder.

Reversing was pretty straight forward with heavy duty relays, but speed control came from switching from
6v to 12v batteries (2 speed). It was almost impossible to make the batteries last 5 minutes, if they did they
were totally flat, so I had a car full of charged spares.

I finally bought 2 littons but to match the torque output of one 12v starter I have to push 36v through both
motors.

That said I would not touch them again ever, even as a weapon drive. I now have reliability, batteries that
will go 3 or 4 fights without charging, speed control, and smaller cables. I also don€™t have a box full of
melted relays.

If you are working to a budget I would recommend scouring the scrapyards for air-conditioning fan
motors from audi or VW€™s, some of these use 12v Bosch motors and are pretty powerful, I know, I have
one that was given to me by a friend and it only cost him a tenner. Visually they are identical to the 24v
Bosch motors used by many builders.

Also dont for get the radiator fan motors ,some of them are quite big ,i got some bosch motors very similar to the 750 GPA a while back.

:)GORD

So David the recommendation of seasoned Roboteers is .... Leave starter motors alone!

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Christian has been helpful in providing a link to one of the best resources for this sort of thing on the web. The fact that you have not read it (you cant have, or youd have the answers to most of your questions) does not give you the excuse to address other people in that manner.

I could provide you with quite a few in depth link describing the relative merits or using wheelchair motors, but you are really not deserving of the time that people have gone to to try and help you.

Suggest we have some moderator attention in this thread before we end up with the second pointless flame war of the week.

Yupo swearing like that is a big no no and i will not be suprised if admin ban his account.

I was trying to help you, but the fact that you didnt read the link is quite obvious, it would have answered most of your questions (including that about the solenoid).

But as Im not easily offended, I will still try to answer your questions. You may also want to look at the Reliance motors from Roger Plant. They may not be the best motors in the world, but theyre fairly cheap and have moderate power.

The choice of wheelchair motors is huge. They can produce anything from 300W to about one horsepower. But most importantly, they already have gearing.

The radiator fan motor in most cars will produce something like 400W if theyre run at their recomended voltage (four times that if you double the voltage). Theyre also quite cheap and might be a good choice.

If you decide to go for them, try finding the motors from an old Audi 100 (they weigh about a kilo more, but peak at about 600W instead).

but i did read the link it said 2 difrent things about the seanoid i couldent tell what it was trying to tell me that i moved the shaft or the gear thaks for the help with the wheel cair motor and the radiator fan motors sory about the last post i had a bad day

one more question about how fast do the whele cair motors go with the gearing what rpm and how many amps do they draw and the same question for the radator fan motor and do either of them need any moding

The fan motors Ive used are from a Peugot 405 (not sure how many of them you will find in the scrappy)

The main reasons I chose these motors are.....

High torque, they are large diameter motors and have some grunt!

relaible, they last forever and so far have not kicked out any EMI of note.

arguements against.....

heavy, 2.2kg each.
back emfs, not too gentle on controllers.

I used mine to spin a 3kg, 18bar up to 6000rpm inside 3 seconds, without gearing. May be a bit underpowered for the current generation of heavyweights, bt using 4 will compensate for that.

I used the very same fan motor for an electric skateboard! Its quite capable of propelling 100kg of me at 12mph (running a 12v motor on 24v, geared 5:1 on 10cm diameter wheels). Motor barely even gets warm.

The Audi 100 type motors produce more torque - but burn out half way to the pub!

Si