Working with my OC3 over the weekend. On Sunday about noon hit the starter button and the starter just "whirled". When I removed the starter to investigate I found that the armature was now in two pieces. Not a good thing!! Was able to cobble together a functioning unit out of spares but the bushings are pretty sloppy. Called on one of the major part suppliers on this list to get a quote on a rebuilt replacement unit. When I explained my situation the first question was are you using a 12volt battery....I indicated I was as I have read in numerous posts that using a 12 volts will not "hurt" the starter and it also makes sure that the cranking rpm is up for a hot spark from the mag for easier starts. Apparently this may not be the case as they are getting more calls for starters as others have experienced armature breakage also when appling 12 volts. I'll let you guys make your own decisions as to what you want to use. But if you are using 12 volts I'd have a spare starter on hand just in case. Oh and just so you know a re-built unit with shipping will set you back a little over $400.00.
Never had 12 volts hurt a 6 volt starter. I would think it takes the same amount of torque to turn the armature shaft when using 6 volts as when using 12 volts. I don't think the shaft is heavier in a 12 volt starter.
What would probably hurt an armature shaft more than anything is too much spark advance.
Thanks Blake, I'll check the advance on the weekend and see what I've got. I also noted that the fracture surface also had the tell-tale clamshell markings of a cyclic fatigue fracture with a oval shear at final failure in the center of the shaft. This occurred at the step out board of the bushing in the face of the starter body. Made me think that possibly the starter had been dropped at one time and without the support provided by the nose cap found in most "modern" style starters, the shaft may have been bent contributing to the failure. I say this but the starter seemed to turn smoothly when engaged with no noticable loading and unloading that one would think might be associated with a bent armature. All the electrics are there to set-up the original 6 volt system. Is there anyone out there that use six volts to start their OC3's? Do find starting your machines any more of a challenge as compared to applying 12 volts?
Hey Tom. Chris here. I run a few machines on the original 6v. and yes, from time to time, in challenging conditions, they can be less effective than 12v. As I am sure you know, the trick on 6v. is to have thick cables with excellent clean connections. Now I look after those connections, and I find I am usually OK. On machines that are kept outside, as mine often are, those connections fade over time. I service them regularly.
Lately I've had a lot of trouble with the solenoids sticking in cold weather on my OC4s. Very annoying. But usually a sharp tap frees them up.
I also have one or two machines where I have rebuilt the old original 6v. components to 12v. - both generator and starter. I sell 12v. HG/OC3-fit generators on eBay once in a while.
On my OC3-31 snowplow I have a 12v. gear reduction starter that I got off eBay. Sticks out the side a wee bit, but it works great.
I sell rebuilt starters for HGs & OC3s for $190-$210 or so + shipping. But I don't have them available all the time. A bit more for OC4 - 3 cylinder.
Although running 12 volts through a 6 volt starter can cause extra stresses electrically and mechanically, usually and in most cases the old 6 volt starters were build robust enough to operate fine if not better with 12 volts applied.
You must consider that when you apply 12 volts to a 6 volt motor the inrush current and subsequent running current will be much higher than the original 6 volt currents. This produces higher RPM and available torque. When the starter is initially engaged the bendix unit will shoot out toward the flywheel at a much higher speed and may impact a hard stop (nose) at the end of travel with enough force to break things. If the engine is exceptionally resistant to rotation the armature shaft will experience higher 12 volt torques which will put extra torsional loads on the shaft. Additionally the motor windings will experience higher heat from the extra currents.
I've stated before that I've run 12 volts on 6 volt VW's, trucks and tractors and never had a starter issue because of it but I know for a fact I am applying more energy to these components that was originally intended. It is of no matter to me. The benefit has outweighed the consequences so far.
We've had a number of bent armatures over the years, but never a broken one.
Running both 6 and 12 v, and all in the last 30 years have been 12 v.
The cause has been kickback, from timing too far advanced, or a second cause - the impulse delay adjustment on the mags getting out of whack.
When this occurs, even with the timing set properly with a timing light, the impulse can let go before TDC, and presto - kickback and bent armature.
Maybe somebody moved the tractor on the starter or foot slipped of clutch pedal while turning engine over with trans in gear.
Actually, the armature shaft broke in the Delco starter on my OC-12 several years ago. No apparent cause - just fatigue I guess.
Blake
This 6v vs. 12v thread will be of interest:
http://cletrac.org/forum2010/index.php?topic=3146.0 (http://cletrac.org/forum2010/index.php?topic=3146.0)