Dynamo Special Setbolt

[Scallops]

Folks,

I noticed my fanbelt was loose today, crawled under to try to adjust dynamo position accordingly and found that the "Special Setbolt" had no nut on the other side. At first I assumed this was why the tension had come off the belt, but looking at this image from the parts manual, is the setbolt (Item #21) "special" because it doesn't need/have one, rather I just need to tighten it from the fan belt side with a 1/4 Witworth spanner? It passes through a threaded hole. Does the end of the bolt "grip" the adjustment slot (part#20)? The diagram shows no nut.

https://www.aulro.com/afvb/images/imported/2014/04/1272.jpg

[123rover50]

Hi Dan

The bolt has the spring and flat washer under the head . That bears against
the slotted bar. It screws into the threaded hole in the alloy part of genny. It should tighten up. I sometimes put a nut on as well to lock it against coming loose

Keith

[Scallops]

Hi Dan

The bolt has the spring and flat washer under the head . That bears against
the slotted bar. It screws into the threaded hole in the alloy part of genny. It should tighten up. I sometimes put a nut on as well to lock it against coming loose

Keith

OK thanks Keith - yes, got the flat and spring washer as per your comment and my diagram.....so I gather you are saying that yes, originally a nut was not included, it just gets tightened from the front and binds into the adjustment slot? If so, I think my fanbelt maybe became loose because the pivot bolt and nut was also loose.....maybe all I need to do is pull out the dynamo and tighten everything up....

Without being a pain, do you know what size nut fits the setbolt? I can't seem to find anything that fits in my collection of random bits and pieces!

[123rover50]

Without checking, its probably 5/16 BSF.
All the mounting bolts have to be tightened after tensioning the belt, especially the rear one where it screws into the block. If its loose the genny can flog around. Check that the spacers are present and correct too.

[Scallops]

Will do. The nut is optional, yes?

[Aaron IIA]

It screws into an aluminium casting. Threads into aluminium should always be coarse. I have only ever encountered 5/16 bsw or 5/16 unc in this position on the generator.
Aaron

[Scallops]

On my diagram, the special set bolt screws into item 20, the slot along which the tension for the fan belt is set. All I want to know is if a nut affixes this bolt on the other side of the adjusting slot (item 20)......is this what you mean by "aluminium casing"?

[JDNSW]

If it is an original generator, it will be 5/16" BSW - and it may have come loose because it was replaced with a 5/16"UNC. While the thread tpi is the same, the thread form is not. And using one in place of the other is insecure. And unfortunately the use of a UNC bolt in the aluminium is likely to have damaged the thread so that it is insecure even with the right bolt. All the more reason for fitting a nut! (and regular checks!)

John

[Scallops]

It's original, and I'm pretty sure my set bolt is too. It's a snug fit in the thread. I don't suspect it's damaged. All my pivot bolts were loose, so I suspect that is why my generator came loose. Happens after a rebuild.

If I can find a suitable nut, I'll use one.

[Killer]

On my diagram, the special set bolt screws into item 20, the slot along which the tension for the fan belt is set. All I want to know is if a nut affixes this bolt on the other side of the adjusting slot (item 20)......is this what you mean by "aluminium casing"?

Dan, on your diagram, the bolt passes through item 20 and screws into the flange on the generator. The generator flange would be the aluminium casing.

Cheers Mick.

[JDNSW]

It's original, and I'm pretty sure my set bolt is too. It's a snug fit in the thread. I don't suspect it's damaged. All my pivot bolts were loose, so I suspect that is why my generator came loose. Happens after a rebuild.

If I can find a suitable nut, I'll use one.

My first job was a vacation job as a field assistant with the BMR. It included daily use and maintenance of several Series 1s. And one of the things I remember quite clearly is having to tighten the generator bolts quite often!

John

[Scallops]

Well, following my first failed attempt at the simplest of tasks - tightening Matilda's fanbelt, it was with some trepidation that I returned to the scene of vast nasal discharge from the week previous and tried again.....



And this time, it was very easy. Yes - idiot me has managed it! :banana:



What I learnt.....



1. Don't attempt automotive repairs, however mundane, under the influence of general anaesthesia.


2. Ask yourself - is it true that anyone who is able to adjust a fanbelt is necessarily a contortionist?


3. If you find the answer to #2 is false, then think about it for even a few seconds.


4. Remove the air filter and battery,


5. Go right ahead and easily adjust dynamo position/fan belt tension.


6. Refit battery and airfilter.



:D