The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: orabanda on 02.01. 2013 02:11

Title: SRM dynamo belt drive
Post by: orabanda on 02.01. 2013 02:11
Happy new year everyone!
After 2,000 miles, the belt has failed!

It is still in one piece (all of the steel re-inforcement wires intact), but some inner teeth and external areas of the material (nylon?) have come away. this resulted in the belt coming off the dynamo pully; therefore - no charge!

Has anyone else had this problem?

I have fitted this system to 8 bikes, but this is the first time there has been a problem.

Richard
Title: Re: SRM dynamo belt drive
Post by: Brian on 02.01. 2013 02:56
What a jolly old nuisance old chap.

I fitted this type to mine

http://dynamoregulators.com/drive-belt-kit.php

The one in my 61' A10 has been in for about 10,000 miles and still looks as good as the day I fitted it.

Hopefully you just had a dud belt or something simple.
Title: Re: SRM dynamo belt drive
Post by: muskrat on 02.01. 2013 13:00
 G'day Richard. Yep had a few go west in no time. A few like yours and a couple snapped. The '51 is the worst offender, the cafe has only eaten one. Can't seem to get the belts here (AT5 420/10) so have a spare in the bike kit and order two more for the shelf.
 I think I found the problem with the '51. The idler shaft isn't real tight in the pinion and floats outwards causing pulley misalignment.
Cheers
Title: Re: SRM dynamo belt drive
Post by: chaterlea25 on 02.01. 2013 14:08
Hi Richard
I have had no problems with the SRM belt drive (touch wood) its been in there 7 or 8 years now!!
I believe belt tension is fairly critical???
As Musky says end float could cause problems!!!

Happy New Year
John
Title: Re: SRM dynamo belt drive
Post by: orabanda on 02.01. 2013 14:45
Gentlemen,
Thanks for your responses.
Please share your adjustment procedure?
Richard
Title: Re: SRM dynamo belt drive
Post by: orabanda on 02.01. 2013 14:56
Just got a response from Gary Hearl at SRM:

"Could be a couple of issues, belt tension too tight when cold, check tension when engine is at temperature and adjust accordingly.
 
If 50w or 60w Halogen bulbs are used, dynamo can overgheat and expand, cauing armature to touch field coil and partially sieze, make sure max wattage Halogen used is 35w.
 
Also pack belt with grease to help lube and keep a little cooler."
 
Title: Re: SRM dynamo belt drive
Post by: chaterlea25 on 02.01. 2013 15:06
Hi Richard,
I have my setup running dry!!!
I set the belt with around 1/4 in slack cold and then checked that it would easily twist 45 degrees when hot
The clamping arrangement wants tighten the tension as the  clamp nut is tightened *problem*
I probably had several go's to get it right  *ex*

HTH
John
Title: Re: SRM dynamo belt drive
Post by: RichardL on 02.01. 2013 18:22
Uh, so rechecking it hot means pulling off the timing cover right after having put it on? Ouch!

Richard L.
Title: Re: SRM dynamo belt drive
Post by: muskrat on 02.01. 2013 19:10
 I don't really like the idea of putting grease in there and I tighten to John's specs. The first time I thought the belt was touching the boss for the inner cover screw in the middle. I ground the boss down and use a counter sunk screw. Had another couple go since then. Heat may be one of my problems as I run a std dynamo and dvr2 on 12v mode for the boyer sparkles. I never use my lights but the dynamo is working at a rate of +4 amps once over 30mph.
Cheers
Title: Re: SRM dynamo belt drive
Post by: WozzA on 02.01. 2013 22:50
Not a solution to your problem, but may be of help to some...
I was put onto this stuff many years ago for belt drives...     wink2
a quick squirt once a year does wonders for the belts..
Title: Re: SRM dynamo belt drive
Post by: bsa-bill on 03.01. 2013 11:38
My tuppence worth - I agree with all Johns comments especially the trial and error with the clamp.
Mine is the SRM one I run it dry apart from the time the reversed scroll idler bush proved it's worth as a pump and tested the belts oil resistance. (it did not slip)
Only issue I've had was one of the side plates came off the large pulley, found it when in there for another reason, no harm done so put it back on and centre popped it around the alloy hub and it's been alright ever since
Title: Re: SRM dynamo belt drive
Post by: muskrat on 03.01. 2013 13:18
 Another product I tried Woz was CRC Belt Grip. Worked good on V's but can't see the point for toothed belts A lube like that (your pic) would be better.
Cheers
Title: Re: SRM dynamo belt drive
Post by: terryk on 03.01. 2013 13:26
I have just always used the original chain set up with grease for years on a number of different bikes. I haven't had any problems with it maybe I lucky.
Title: Re: SRM dynamo belt drive
Post by: bsa-bill on 03.01. 2013 14:58
I had a Flash for maybe two years in early sixties and recall at least three chain replacements, but then I was a young lad learning about things like chain and belt tension and the fair sex, some learning curves are steeper than others I guess and 50 years later I can now do chains and belts  *smile*
Title: Re: SRM dynamo belt drive
Post by: metalflake11 on 03.01. 2013 17:10
I ran the same chain and sprockets for donkeys years with hardly any maintainance or adjustments ever needed. Back end of summer last year, on a whim, I put an S.R.M. belt kit on, after hearing all this I am begining to wonder if I have been wise?
 They advise running it in grease so I do just that, but it does seem an odd thing to do!........... It's like their comprehensive engine re-build guarantee, which is only valid if you run it on straight oil and NO filter. I don't understand that either!........... The bike still has a cartridge filter fitted and it would take very little time, effort or cost to plumb it in, but I don't.
I suppose my point is, for every A10/A7 I have built they will have done 100's. So for me, I ask the question and argue my point of view sometimes, but at the end of the day I follow their advice to the letter. Tens of thousands of miles with very little trouble back their views up. For me, adjust it like they say and pack it with grease!
Title: Re: SRM dynamo belt drive
Post by: Slide on 04.01. 2013 23:03
Hi
I very recently fitted a toothed belt kit restoring my first BSA  - an A7SS. I used the kit from DynamoRegulators. I checked it after only 100 miles when fixing an oil leak and noticed a bunch of hairy metal (looked like wire wool) that had collected around the end of the dynamo shaft.  It was held there by magnetism and was steel reinforcing stripped off one side of the belt, presumably due to the edge of the belt rubbing somewhere. From this short experience I'd say it is not only important to make sure the pulleys aer aligned, but also check the sides of the pulleys are good and are not distorted or sharp-edged. I've now done some precautionary smoothing/rounding of the pulley flanges with emery after what happened. It's back together and running, belt itelf looked ok and was re-usable.
I noticed the sides of the small pulley on mine are made of thin alloy which is easily bent out of shape. I found it is important to use a proper screw-in puller when removing the small pulley to avoid damaging it..

Final bit to add: Because the large pulley attached to the idling gear is oversized with these kits, I found there is very little clearance to the casings. I had to do some trimming of the timing cover internal surfaces in places, to get the cover to fit nicely withouit fowling the edge of the large pully - another potential souce of belt damage.

Happy two-wheel motoring

Mark
Title: Re: SRM dynamo belt drive
Post by: RichardL on 29.08. 2013 15:35
Well, this seems like the topic I need to be in. On the possibility that noise would be reduced by installing a dynamo belt drive, I am in the process of installing the SRM version. I think this might have turned into an if-it-ain't-broke-don't-fix-it project.

There is, maybe, an interesting story of trials and tribualtions to come out of this but, right now, I have a question. The nut retaining the dynamo sprocket didn't come off that easy. With the dynamo on the bike, I improvised an impact-wrench approach (whacked a socket speeded with a sledge hammer), which worked due to the strength of the chain tranferring the force to the engine. So, with the belt drive, what happens when you want to remove the SRM nut? Is the belt as strong as the chain when it comes to this kind of abuse?

Richard L.
Title: Re: SRM dynamo belt drive
Post by: bsa-bill on 29.08. 2013 18:31
it's a taper as you know, if you can get an L shaped lever behind the sprocket/pulley and apply some force by levering against the inner case then a light tap with a hammer will spring the taper.
Always worked for me
Title: Re: SRM dynamo belt drive
Post by: RichardL on 29.08. 2013 19:14
Bill and all,

It really surprised me how tight the sprocket was on the dynamo. It took a s***-load of puller tension and a bit of torch heat to get it to let go. I was surprised that the sprocket didn't get bent in the process. BUT, that wasn't the question I was asking. What I was wondering about was how difficult is it going to be to remove the nut that secures the SRM belt sprocket to the dynamo? I am wondering if the belt can provide all the holding force when loosening the belt-drive nut like the chain did for the chain sprocket nut?

Richard L.

Title: Re: SRM dynamo belt drive
Post by: Briz on 29.08. 2013 19:37
The best way is to lock the sprocket with a diagonal bar between the sprockets. Works fine on belt drives too; just be sure not to damage the ally teeth.
When pulling obstinate tapers off, dont just use puller force. Crank some tension into the puller, then hit the centre bolt with a hammer.
Title: Re: SRM dynamo belt drive
Post by: RichardL on 29.08. 2013 19:40
More about this dynamo belt conversion:


OK. Back to work.

Richard L.
Title: Re: SRM dynamo belt drive
Post by: RichardL on 29.08. 2013 19:42
Good tip. Thanks, Briz.
Title: Re: SRM dynamo belt drive
Post by: trevinoz on 29.08. 2013 22:18
Richard,
                it sounds as though you should be wearing a blue and white striped apron!
When you reassemble, use sealed bearings. The drive end bearing is usually loose in the housing so a little Loctite is advised.
Didn't you hold the armature in a vice to remove the comm end circlip?
Sometimes the comm end bearing can be levered off with two screwdrivers between the bearing and the commutator, after inserting steel packers.
If this doesn't work, a small bearing seperator does the job.

Trev.