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View Full Version : TR4/4A Replacing brushes on TR4 generator



Scotsman
02-12-2014, 10:32 PM
Any tips on replacing brushes on a TR4 generator. Bentleys makes it look simple but sometimes looks can be deceiving. Note, the generator works fine. I just want to be sure the brushes are not worn to the point that the commutator is being damaged. If they are OK I will leave well alone.
Also while in there is there anything else I should be checking out/replacing.

While I am on the subject of generators. Is the stock generator sufficient to power halogen head lights. I wont be running any other extra peripherals. Earlier posts give mixed answers.

TR3driver
02-13-2014, 12:53 AM
Ain't broke ... don't fix it.

But the book calls for periodically disassembling, to lubricate the front bearing. Clean and inspect while you're at it.

HerronScott
02-13-2014, 08:44 AM
I ran 55W halogens with a generator in my TR4A along with a more modern radio and external amplifier for years without issues. Everything else was stock.

Scott

Geo Hahn
02-13-2014, 10:34 AM
Pretty straight forward -- I seem to recall that you can sort of **** the brushes in there carrier/opening (with the springs pressing on their backside) to hold them back while you get the armature into the rear plate -- then reach in with a small screwdriver and tip the brushes into position.

If you keep the rear bearing lubed these units seem to last a long time (forever).

You might be able to assess the wear on the brushes by peeking in the backside -- I think you can sort of see where the outer end of the brush is and get an idea how much is left. In my experience those brushes wear verrry slowly.


Ha ha -- what you do with the brushes to hold them back is start them in the holders slightly crooked so they don't go fully home, then straighten and release them once the armature in in place. I explain as my worded for 'slightly crooked' is offensive in some contexts.

Scotsman
02-13-2014, 02:36 PM
OK,

Based on Randall's response "Ain't broke ... don't fix it", I wont open it up (unless someone has strong opinions otherwise). I only asked because the manual recommends to periodically check brushes for wear. The brushes for my wiper motor were worn all the way down to the "arms" that held them, and the commutator was being ground down. Fortunately it was still working and I was able to replace the brushes in time.

trrdster2000
02-13-2014, 03:29 PM
Scotsman, if you really would like to get the full Monty on the head lights, get the heavy duty wiring harness from one of the supply folks or at least put in the grounding block at the front of the car.

Wayne

TR3driver
02-13-2014, 05:57 PM
Based on Randall's response "Ain't broke ... don't fix it", I wont open it up (unless someone has strong opinions otherwise).
Apologies, I was being somewhat flippant. I do suggest cleaning and inspection, just not necessarily replacing the brushes. As noted, they last a long time; mine appear to still be original and have outlasted both bearings.

Especially if the car is new to you, pay particular attention to the mounting points. It is very common to find the mounting holes worn oblong from working loose, or even the threads stripped in the extension block for the front mount. It's not too hard to repair these areas if the damage is not too far gone, but if left untreated, eventually the generator ears will break off and necessitate a new generator. I reamed the mounting holes back to round, and inserted sleeves of hard brass tubing (held with Loctite).

When reinstalling the generator, be sure to do the final tightening on the front lower bolt after having set the belt tension and tightened the upper bolt. It cannot be left loose enough to allow any movement (including adjusting the belt) or it will vibrate loose. Not easy to reach down there with the belt in the way, but it can be done. Also note that the top bolt should be double-nutted. You tighten it into the threads in the generator first, and then tighten a nut up against the other side.

I'm also running 60/55 watt halogens with the stock TR3 generator (which is even smaller than the TR4 version). I would say that it depends on your usage as to how acceptable that is. A lot of short trips with the headlights on, or a lot of winter driving (headlights plus wipers & heater) can cause problems even with the originally supplied 36 watt sealed beam headlights (which I believe are NLA). One of the books even recommends recharging the battery after a winter run, presumably to ensure it has enough charge in it to prevent freezing.

Geo Hahn
02-13-2014, 06:49 PM
...Also note that the top bolt should be double-nutted. You tighten it into the threads in the generator first, and then tighten a nut up against the other side...

I'll add that you might also verify you have the locking tab washer on the bolt that holds the generator bracket arm.

https://i1214.photobucket.com/albums/cc499/Ahwahnee18/TR3/LockTab1.jpg

Mine was missing from my TR3A and sure enough I arrived home from a trip to find the bolt gone and the generator taking a lot of abuse from insecure mounting. I made one for that car (with a bench grinder) from a fender washer:

https://i1214.photobucket.com/albums/cc499/Ahwahnee18/TR3/LockTab2.jpg

Darrell_Walker
02-13-2014, 07:14 PM
Mine was missing from my TR3A and sure enough I arrived home from a trip to find the bolt gone and the generator taking a lot of abuse from insecure mounting. I made one for that car (with a bench grinder) from a fender washer:

https://i1214.photobucket.com/albums/cc499/Ahwahnee18/TR3/LockTab2.jpg

I see you took the belt and suspenders approach and also put a lock washer under there!

Scotsman
02-13-2014, 10:06 PM
Thanks for the additional feedback. I'll take a peak and see what I find. My car is actually a 59 TR3A, but I referenced the TR4 as I believe it is the same or similar to that on the TR3A. At least it looks as though it is.
Bentleys TR2/3 manual shows the earlier model generator with "windows" in the casing to allow access to the brushes.

TR3driver
02-14-2014, 01:47 PM
The cover band & windows were deleted in 1956, but the generator was functionally identical (model C39PV-2, rated 19 amps max) until 1960 (TS60000) when it was replaced by a model C40/1 rated at 22 amps. (According to Lucas, a few models got a model C40 generator, Lucas part number 22700, but that doesn't seem to be mentioned in the TR literature.) The C40/1 was slightly larger physically, instead of being straight, the body was larger over the windings at the front and necked down in the brush area at the rear. The fan was slightly larger as well. Connections were different, quick-connect tabs instead of studs. The control box changed and Lucas warned that it must be swapped in pairs with the generator; but I don't see any harm in using an early control box with a later generator (except you'd only get the 19 amps).

OTOH, I sure burned up a lot of generators "back when", using a later generator (rebuilds seemed to always be the later version) with an early control box. I doubt the control box model had much to do with it, more likely it was because I had turned up the output to try to keep the battery charged (in winter with a lot of short trips at night). But maybe Lucas knew something I don't.