Tach generator gearbox

[markberry]

Hi All,
while SaxMan has a thread going on right now about His Tach Drive Generator, I was wondering if any of you have disassembled and lubed the drive gearbox? I'm not even sure if these things need to be lubed; But I doubt it has been lubed in the last 55 years. I'm getting close to firing this thing up after 8 years of sitting and I'm starting to think about all the things that might have dried up and/or might be due for some preventative maintenance. I've heard the reproductions of these gearboxes aren't very robust so maybe taking care of this one might be the way to go.
if anyone knows anything about disassembling and/or lubricating these, I'd appreciate the info .
regards
Mark
P.S. figured out my bonnet prop question from last week.

 

[AN5Sprite]

They need to be lubed. That's what the screw on top is for. What should you use....? Heavy oil, thin grease? I settled on JD Cornhead grease. I'm using it in a modern repro though. Then again if it can keep that piece working I'd think an original unit would like it too.

Also, I've been using John Deer Cornhead grease in my tach-drive for 4 years without any problems. First I disassembled the unit and lapped the mating surfaces on a granite surface plate. Then made a thin paper and silicone gasket. Lubed the inside and reassembled.

I did this because I've had a number of these things, new and old fail. The new ones that failed all failed because there was virtually no lube inside and what was there leaked out when it warmed because the the halves of the case did not fit together. The old ones that I lost usually went because of a problem with the generator or a problem with dummy working the wrench. (me)

 

[markberry]

thanks Steve. I'll look for the screw in the top. anything to look out for if I take it apart?
regards
mark

 

[AN5Sprite]

Na, nothing to fear in there. No springs or anything loose. I'd just look for wear and if none is present, clean and lube it then put it back together. On the old ones the cases seem to fit really well so there's no need to COMPLETELY disassemble or do the lapping I mentioned. I'd only do that to the new ones.

 

[smaceng]

I had one seize on my startup and it threw itself across the garage. Lucky I was not in the path

 

[markberry]

Na, nothing to fear in there. No springs or anything loose. I'd just look for wear and if none is present, clean and lube it then put it back together. On the old ones the cases seem to fit really well so there's no need to COMPLETELY disassemble or do the lapping I mentioned. I'd only do that to the new ones.

Thanks. I think I'll open it up then and grease it since it doesn't sound too fiddley.
Regards
mark

 

[markberry]

I had one seize on my startup and it threw itself across the garage. Lucky I was not in the pathView attachment 40369

Jeeeeez! I would have thought something would strip or shear internally before ripping itself free from the generator! I'll move the "lubricating the tach generator" up on the priority list of "before first start tasks".
thanks for the heads up!
mark