MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Tachometer Gearbox Issues

Would you believe that over-greasing the tachometer gearbox can turn off the generator? Have a look at http://www.ttalk.info/Tachometer_Gearbox.html . Bud
Bud Krueger

Hi Bud and others,
Does the TD or TF manual specify grease or oil in the tacho reduction box? The TC manual does not say apecifically, but W.E. Blower specifies gear oil in "The MG Workshop Manual." In the chart at the back of the book, there is an identical diagram to that in the TC manual except for the words "N.O.L 140 gear oil" where there is a blank space in the TC manual. I use oil but it obviously leaks a lot. A company named "Penrite" make a lubricant which is between grease and oil. It is for leaky steering boxes in old cars. What do you guys use?
Bob
R L Schapel

Bud,

Looking at the photos in your article, I notice that the armature seems to be wrongly placed in the generator body. The wear pattern on the commutator shows that it is too far forward by about an 1/8 to 3/16 of an inch. I also see that the section of the shaft that fits in the rear bush has the same wear pattern. It may be that there is a missing spacer at the pulley end.

John

J Scragg

Bob, as I mentioned in the article, the only reference to lubing the tachometer gearbox is section 5 on Page P.5 of the TD/TF WSM. That would make it grease to Ref.D on Page P.2, viz., the same grease as used in the steering and kingpins.

John,I took notice of what you saw. I last assembled the generator along with the replacement of the armature. See http://www.ttalk.info/Holcombe.htm for details. Unfortunately, I can not find a diagram showing the detail of the parts that go onto the pulley end of the armature. There is a spacer, about 1/8" thick, that is part of that group. Could well be that I have it located on the wrong side of the pulley-end housing. Bud
Bud Krueger

Bud,

I have just checked my spare generator, which also has a Holcombe armature and it looks just like yours. After rebuilding it I fitted it to my car and ran it for some time, it works fine. At the commutator end there is an airgap (between the rear plate and the armature) of about 1/8 inch, which means that the thrust washer doesn't do anything. I have kept all the old parts and will compare them with the new ones, when I get time.

John
J Scragg

Hello Bud, If you do move it back, make sure it does not jam and/or put rearward pressure on the tach drive coupling. Also make sure the windings don't hit the brush holders. It does seem thick oil would lubricate the bushing better than grease. May be best to unscrew the drive when lubricating? George
George Butz III

Bud, JFWIW, when I rebuilt(actually just took apart, lubed with Lithium grease and reassembled) my tach drive, I opted for the simplicity of screws and nuts because I haven't the skills to install rivets. This system as served me well, especially last fall when I took it apart and reassembled it a second time.

Jud


ps: all of a sudden, I can't seem to upload a picture. I'll try on the next post.
J. K. Chapin

Some years ago, our tach quit working. A quick inspection disclosed the tach drive dangling on the cable along with the threaded end of the generator. It had cut the end right off. I concluded the screw worked loose and then the screw and shaft eased forward enough where the screw became a cutting tool to sever the end of the dyno off.

That was part of the incentive to try out the new alternator, but the tach drives will not insert into the one I received. I will be removing and dissecting the alternator to remove that short shaft and open it up.

I also lost the pulley off the front of a generator. Upon examination, the actual armature shaft was drilled in front and a short shaft that the pulley fit on, was turned down to fit into the armature hole and then they were crossdrilled and a tiny pin inserted to join the two. It snapped at that pin because there was virtually no metal left. That was just an accident waiting to happen.

This sure lowered my opinion of Lucas engineers (or maybe lack of using real engineers), along with the logic of using a bearing on the front of the armature and a bushing in back that requires an oil cup.
JIM N

Bud, here's the picture I tried to upload. Turns out the upload dialog box got hidden behind about three layers of windows and I didn't realize it was already open. Clicking on upload didn't work because the dialog box was already open.

Jud

J. K. Chapin

Jim, Whatever you found at the front of your armature was not factory. Sounds like someone repaired it at some time. Originals were one piece. The tach drive mounting was not one of the finer points of design on our cars. Lots in the archives about correcting and improving this. Unless you overtighten the belt the bearing/bushing set up will work for many miles. George
George Butz III

I realised I have a TF "Operation Manual" in my stuff and looked up "lubrication" on page 44. I attach an image of the cover and will attach an image of page 44 in a few minutes. Perhaps oil and grease might have both been acceptable for the tacho gearbox?
Bob Schapel

R L Schapel

Here is an image of page 44. "Every 6000 miles apply a grease gun filled with oil to ref B (page 36) to revolution indicator gearbox on dynamo." Ref B is gear oil for gearbox, steering and rear axle (Hypoid 90).
It would be interesting to find the earliest reference to grease. They probably started recommending that when they realised that oil seeps out in a short time?
Bob

R L Schapel

Image of page 36. The chart at the back of the book also confirms "Greasegun filled with oil" to steering.

I can not find a date on the manual, but is marked "First Edition" which might explain why it mentions oil instead of grease? Interesting if nothing else. There are similar interesting bits in the TC manual.
Bob Schapel

R L Schapel


Bud, There is a split ring about 3/16" wide that fits on the front of the armature shaft in a groove on the shaft. It is partially covered by a sheet metal cap to retain it from popping out of the groove.

This part is shown clearly in your article on the Holcombe. I'm sure your aware of it since your article shows it, but reason I bring it up again is that my Holcombe armature came to me in its original kit box with this part missing. Apparently removed when they rewound the armature and never replaced.

I could not find this part anywhere and ended up making my own from a piece of steel tubing, split and squeezed into the armature shaft groove.

If this part is missing, the armature will not be properly positioned in the case, and the fiber thrust washer on the rear will not cover the end gap where all of the grease is coming through.


Richard Cameron

Rich, we're thinking along the same wavelength. That cap is mentioned in conjunction with that image. I'm quite certain that I installed the cap. It turns out that the only pieces that physically locate the armature in the housing are the slit ring (w/cap) and its butting up against the inner race of the bearing. I'm beginning to wonder where I located the 'spacer'. The other issue is where that cap is situated. I mention in the Holcombe article about pressing it onto the split ring.
You have me puzzled about the 'fiber thrust washer'. I don't recall seeing it. Such a thing could well be what's needed to keep the grease off of the commutator. I'll be opening up the generator in the next couple days to see what I can find. Thanks - Bud
Bud Krueger


Bud, Yes, Page N.5 under Electrical Equipment of the Workshop Manual shows the washer and calls it a thrust collar. My generators (5) all had a fairly thin fiber washer serving as this part.
Richard Cameron

Yes, I see it!! It'll be interesting to see if one's in there. Thanks Rich. Bud
Bud Krueger


Bud, If one considers the design of the front generator mount plate to the armature arrangement, and all of the parts are correctly assembled, there should be no fore or aft end play on the armature once the pully nut is torqued. Therefore, it seems to me, the rear fiber washer we were speaking of really doesn't serve as a thrust washer unless there is front bearing play/failure. It would however, to some degree, serve as a shield from grease entering the case from the rear brass bushing. Also of interest, none of the normal MG TD parts houses seems to list the fiber washer for sale or show it in their illustrated parts breakdown.
Richard Cameron

Right, Rich, but the operative word is 'correctly'. I can not find a comprehensive listing of all of the components that that are on the pulley end of the armature. It would appear that the 'cap' on the split ring, in contact with the bearing inner race, sets the location of the armature. Nothing at the brush end can control it. I may try to fix that 'thrust washer' in place to keep the grease out. Bud
Bud Krueger


The cap is very thin pressed steel sheet, so it doesn't provide much space added to the split ring. I never found one listed in any parts houses, and Sundries kits weren't available at the time. Its possible a generator /starter repair facility might have one on an old armature, but I didn't check because we're so rural here that there were none close to my home.
Richard Cameron


Bud, attached is a pretty good Illustrated break down on the generator front end. The rivets on the bearing retaining plate have to be drilled and replaced with machine screws/ nuts when renewing the bearing. If yours are still riveted in your generator, its a good bet the bearing is old and not lubed. The pulley spacer is fairly thick as I remember.

Richard Cameron

See http://www.ttalk.info/Holcombe.htm and you'll see that I used screws and nylocs. That's a great sketch. May I ask where it's from? Thanks. Bud
Bud Krueger


Its not a MG TD Generator---- Just a C-42 common Lucas one. I googled "Lucas Generator Assembly Drawing". From Images they show.
Richard Cameron

I found this on the Midget and Sprite web site

http://midgetandspriteclub.com/wp-content/uploads/2016/06/C39_dynamo.pdf
Richard Cameron

Today I took Lazarus for his January run. Hard to believe the display on the Ammeter after the cleaning. It was showing close to 30 amps above 2000 rpm. I haven't done any checking, yet. We're scheduled for a bit of snow tomorrow, so this was possibly my last chance for the monthly run. I'll hook up some external meters to prove/disprove the indications. Amazing what can happen when the brushes actually contact the commutator.
Bud
Bud Krueger

This thread was discussed between 22/01/2019 and 28/01/2019

MG TD TF 1500 index

This thread is from the archives. Join the live MG TD TF 1500 BBS now