School me on engine starters

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Brian Rupnow

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Up until this point I have built my engines with no provision for starters except a "starter hub" which bolts to one end of the crankshaft and is engaged by my 3/8" variable speed drill. I am now thinking about a "built in" starter which becomes part of the engine package. It would have to be powered by the same 12 volt battery which runs my ignition coil. I don't want a remote starter that is hand held and drives with a friction wheel or belt. I googled this and got about a million answers, so I am asking members of the small i.c. engine world for a recommendation.
--Brian
 

werowance

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I always thought that a one way bearing pressed in a gear that rides on the crank shaft and a smaller gear on the shaft of a old used battery drill motor might work. never tried it but just something I have thought about. that way you don't have to mess with a Bendix that flys in and out and the gears grinding etc... still holding onto a Makita drill with stripped gears just for the motor in it for this purpose. if I ever get good enough to make an engine that I could use it on.
 

Brian Rupnow

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Werowance--that would work but I'm thinking of a solution that I could just buy and bolt in place. Yes, it would need a one way clutch bearing so that once the engine started the starter motor wouldn't impose a load on the engine.
 

Tom 1948

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Will you have a charging system ? In the real world you can get many electrical starts before it pulls the batteries down.
 

Mike1

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Model Marine, and RC Car engines are fitted with a pull recoil starter which acts on the engine crankshaft, I don't know if they could be adapted for your engines, probably may need a engine designed around the starter.
Just a thought.
Mike 1
 

werowance

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you know this just reminded me, the traxxas dune buggy I used to have had a battery starter on it. u just inserted the battery pack thingie into the top and pushed the red button until it fired up. actually powered the glow plug and everything. unfortunately I do not have that buggy anymore but I bet I can find pictures of it.
 

werowance

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some google pictures, traxxas easy start

upload_2019-8-15_16-8-13.png
 

Brian Rupnow

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Tom--My engines are stationary engines and the ignition comes from a 12 volt garden tractor engine. I recharge it when necessary.--Brian
 

Charles Lamont

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Right at the start of this clip, an E T Westbury Seal (15cc) is started by a motor that is more or less to scale. I am amazed.


It looks as though it may be similar to the ez-start motors werowance posted, which seem to be available for $/£10 or so.

What are these things?

PS: I have identified that motor as a Graupner Speed 400, which has a case about 1-1/2" long.
I am still staggered that something that small will crank a Seal into life.
 
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XD351

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I remember when those Traxxas cars came out with push button starting - man that was convenient but it came at a cost - weight which slowed them down and made them corner sluggishly , but very cool anyway !
Here is a video showing a commercially available motor from everybody’s favourite country -PRC.
It uses a one way bearing on the crank to allow the starter driven gear to free wheel once the engine starts .
The engine starters i used for my model nitro cars used twin 540 dc motors to start the engine and one of these with a reduction gear would start a small ic engine easily
 

dnalot

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To get around issues of scale way not have the engine run a generator that can be used as a motor to start the engine. That's how the starter for my RV generator works.
 

ALEX1952

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The one way bearing referred to by XD351 is called a spragg clutch, and I believe that is the correct spelling.
 

bluejets

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PS: I have identified that motor as a Graupner Speed 400, which has a case about 1-1/2" long.
I am still staggered that something that small will crank a Seal into life.
If one takes a look at the reduction gearing both through the motor gearbox and then the pulley reduction, I'd say it would be in the range of 100:1 so, not really surprising.

All it takes for the engine to start is a cranking speed around 300-400 rpm.

Carby needle adjustment looks awfully close to that spark plug though...ouch!!!
 

Brian Rupnow

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I looked at the Graupner Speed 400 and it appears to require a controller. Will it run from a 12 volt car battery with just a momentary contact push button switch? I can buy a one way bearing from Torrington. I can machine my own gears and mounting brackets.
 

bluejets

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I looked at the Graupner Speed 400 and it appears to require a controller. Will it run from a 12 volt car battery with just a momentary contact push button switch? I can buy a one way bearing from Torrington. I can machine my own gears and mounting brackets.
Motors usually run on 7.2V nicads but 12v for a short burst such as shown with the Seal engine should be no bother, especially with the gear reduction shown there as I mentioned above.
Any switch directly wired to the motor would need to have a hefty current rating and most electronics push buttons are only rated at low amps.
One could use the small electronic type to operate a relay (10A) and then the relay from the battery to the motor.
 

Jennifer Edwards

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I agree with Bluejets,

I am not only a model engineer but also a ham operator, and build amplifiers with very high voltage and currents that requires switching on and off during transmit and receive.

For this I use some pretty specialised relays. But the purpose is the same to switch a lot of current quickly with a small underrated device.

A relay in the starter motor circuit would be prudent. In effect it is the same function that the Solenoid on your automobile performs.

Jenny - KQ4U
 
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gbritnell

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To get the required torque to start an engine and keep the starter motor size somewhere in the bounds of practicality a large gear reduction would be required. I don't remember what the operating rpm of the RC car motor is but it's in the thousands of rpm's so by gearing it down you can get the required starting speed plus the needed torque. The problem is the size of the motors. If you look at the thread about building the Harley engine by Terry Mayhugh you can see how he incorporated an electric motor into a starter for his engine.
gbritnell
 
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