Starter/generator question

MFDAC

MFDAC

Tractorologist
Senior Member
Member
A co worker is building a Struck mini dozer from a pile of parts with lots missing. He's got a long way to go but is getting close to it running at least.

FJ struck.JPG

He asked me the other day if a automotive generator can be used for the starter/generator. I didn't have an answer. Logic told me yes but I'm not certain!
Anyone have an answer for me?

I know nothing about the Struck, if that is how they were originally. A 8 hp Tec with a pulley on the flywheel came with the basket case and it appears it was set up with that engine. He said there were brackets for a starter/generator setup with the engine.

Thanks in advance for any info on this subject.

DAC
 
I agree with Lance. If he needs one find a junk yard with the older cars and trucks. They are a lot less expensive than buying one for a tractor. Delco Remy are good ones.
 
If you just wanted a generator to charge the battery a regular 12 volt automotive generator should work fine if you find one that is wired the same as the one in the picture of the generator wiring I have attached. If you are wanting it to work as a starter as well as a generator I would strongly recommend that you find a true starter generator or devise some other means to start the engine. If you do decide to go shopping for a true starter generator be aware that starter generators were made to rotate in either a clockwise or counterclockwise direction and this direction cannot easily be changed so make sure you get one that turns the correct way. Also be aware that generators are not designed to be run backwards due to the way the brushes engage with the commutator.

I will assume that we are talking about the Delco Remy brand of starter generator versus a regular automotive 12 volt Delco generator as to my knowledge they were the only supplier that manufactured a starter generator in North America that can be found on a lot of small engine applications – they actually called it a motor generator. I believe that Bosch offered a similar Dynostart unit that was common in European applications. I am familiar with the Delco Remy starter generator used on a Wisconsin TRA-10D engine to start the engine and charge the battery once the engine is running. While the units may look very similar to a regular 12 volt Delco generator they are wired differently internally and originally the two field coils were quite different in construction - some of the rebuilt units offered today may not use the original style field coil for starting. Since the starter generator was a combination starter and generator it was designed as a compromise to be able to do both jobs in my opinion. The one field coil that is utilized mainly in the starting process was originally constructed as a ribbon of flat metal that current flows through before it reaches the non grounded brush – it is wired in series with the armature. I assume that one of the reasons it was made out of such thick material was so it would have very little resistance to the current flowing in or out of the starter generator. The other field coil consisted of numerous turns of much lighter magnet wire which assists a bit when rotating the armature during starting but its main purpose is to control the output of the SG when it is running and acting like a generator – it is wired in parallel with the armature. I have attached pictures of the two field coils so you can see the difference. I have also attached pictures of both the starter generator internal wiring as well as how a Delco generator for an automotive application was normally wired. The true generator utilized both field coils to control the output and was not really designed to act as a starter motor – both the field coils are connected in series to each other and in parallel with the armature. While a generator can be powered with 12 volts and will run like an electric motor my concern would be that it would not have enough torque to start a hot engine rotating from a fully stopped position. If you study the wiring on a regular generator as shown in the picture you will see that both field coils are connected in series rather than the series parallel set up that is shown for a starter generator. There are other generator internal configurations that were used but I believe this is the most common that was used for automotive applications. A generator may be able to start a cold fully stopped engine but I would think they might tend to struggle and eventually fail as things inside got hot during the process – the sizes of the drive and driven pulley would also be a factor in starting as well as what speed the generator armature would rotate at when the engine is running at wide open throttle - just my opinion.

1 Schematic Drawing Of Original Starter Generator Setup.jpg 2 Common Delco Generator Internal Wiring.jpg

3 Field Coil Wired In Series Used For Starting.jpg 4 Field Coil Wired In Series Used For Starting.jpg 5 Field Coil Wired In Parallel Used For Charging.jpg

6 Field Coil Wired In Parallel Used For Charging.jpg
 
Thank you all for the comments!

29 Chev, may be just your opinion but it is very valuable information! I still drive a truck with a generator on it so at least know a little about the generator. I also have a couple of starter generators around here, but never knew there was a difference. Now with this information I think we can get a starter system set up for his Mini Dozer---Thanks again!

DAC
 
MFDAC said:
29 Chev, may be just your opinion but it is very valuable information! I still drive a truck with a generator on it so at least know a little about the generator. I also have a couple of starter generators around here, but never knew there was a difference. Now with this information I think we can get a starter system set up for his Mini Dozer---Thanks again!

DAC
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Glad to provide the information. If you are interested I did a thread on another site that shows a starter generator that I repaired to have as a back up unit for my Bolens 1053. It contains links to the Delco Remy Motor Generator service manual and other reference materials.
Delco Remy Starter Generator Used On Some Bolens Tube...
 
I think that 29 Chev knows what he is about. As an aside, I worked many years ago as a young mechanic in a garage that had a customer who had restored a 1923 Dodge touring car. It had a starter/generator that was original. The S/G unit was a large square block unit that was gear driven. It worked very quietly and efficiently. So, starter/generators have been around a long time.

Sheenist
 
sheenist said:
I think that 29 Chev knows what he is about. As an aside, I worked many years ago as a young mechanic in a garage that had a customer who had restored a 1923 Dodge touring car. It had a starter/generator that was original. The S/G unit was a large square block unit that was gear driven. It worked very quietly and efficiently. So, starter/generators have been around a long time.

Sheenist
Click to expand...
Very interesting comment, Sheenist! Yes I'm sure 29 Chev is right on with his info! Thanks for the reply!

DAC
 
I ended up having one laying around here that had the same model number as the one you rebuilt on the thread at GTT, @29 Chev ! It spun nicely but had a bent pulley. He said he had a pulley. Still waiting to hear if it is going to work for him. Thanks for your help!
gen1.jpg gen2.jpg

DAC
 
29 Chev said:
Should do the job with a different pulley as long as the armature is not bent at the end from whatever bent the pulley and it rotates in the correct direction for the Tecumseh engine.
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That pulley was worn paper-thin so it didn't take much to bend it. Obviously that unit has a lot of hours on it. Should know tomorrow if it works. I don't remember where I got it. Probably have had it laying around the shop for 25 years or longer. Your info at GTT is the only way I would have ever known it was the "real deal". Thanks again!

DAC
 
MFDAC said:
That pulley was worn paper-thin so it didn't take much to bend it. Obviously that unit has a lot of hours on it. Should know tomorrow if it works. I don't remember where I got it. Probably have had it laying around the shop for 25 years or longer. Your info at GTT is the only way I would have ever known it was the "real deal". Thanks again!

DAC
Click to expand...
Attached is a two page pdf of the motor generator numbers and specs that Delco Remy produced for small engine applications that may help you if you encounter another model number (as long as it is still the original configuration and someone has not changed it internally). To my knowledge they were all made as 12 volt units except for one which was made as a 24 volt unit as per the pages.
 

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