That is some very interesting reading, it explains a lot of bearing failures. I'm glad I do not have these sort of issues with my engine as I play up to 6,000 rev's

Rob

The real shame of this is that tensioners are used nearly all cars and last fine but when it comes to pretty bolt-on bits they seem to be designed by artists rather than engineers they look pretty but a bit of simple engineering know how would make them work. 

It took me 5 minutes talking to the guy on the counter of a bearing supplier to get the information needed to make a decent tensioner yet all these suppliers seem unable to do that

Re Chinese made parts there is nothing wrong with them per se so long as good Q&A is applied and that is where it slips up the MST kit comes from the States with a Chinese bearing supplied so no idea if it is any good or not. There are many other avoidable design flaws as well

The main point I was trying to make was that smaller bearings of a good spec with a cover to give a good diameter is far better than a larger bearing, just like the one Peter built for H

Modern cars have a small bearing and a plastic wheel mounded round the outside of it. Perhaps something like that can be made use of.

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Thought I would bump this topic again.


Been meaning to sort out my permanent replacement for the last few months as the bearings failed again last year, the grooves that hold the cir-clips have worn away and so not holding the replacement bearings in place etc. Well last week Gordon (Roadrunner) and I got onto the case with order all the required bearings etc. Most parts are in but just waiting on a  sleeve to adjust the original shaft to the inner diameter of the new bearings which like most folks have done will be the actually "pulley"......


Watch this space......

It may be worth researching tensioners on production cars that would just need a bracket made as theses usually do the 60,000 miles before changing and they run at speed as most cars will pull more rpm than a beetle.

I had forgotten about all this and am sorry to hear Andrews had issues, the little
bearings that are supplied with this stuff are really no use at all.

I think I made a pulley to house Hunters 47mm diameter bearings as they were all I could find
at work, they are 'deep groove' though which is a very important point.

Dave Dream made his own set up and as far as I know its all going ok, sometimes we should also remember
that some maintenance is needed to ensure these things survive, something I know Hunter does, he takes
the pulley off and gives the bearings a good soak in oil and fills them with grease after that.

I think I mentioned that these deep groove bearings can be got now in many sizes well above 52mm, which is
an unbelievably common size, they arnt expensive at all and definitely worth looking at even 70mm diameter if
they will fit.

The idea here for those that may not have read this thread is that the larger the diameter the bearing or pulley
is, the slower it will be revolving.

I favour the way Dave Dream has done it, he uses deep groove bearings and there are two of them, the belt runs direct on the
outer race, the reason I prefer this over the use of a housing is that the actual outer race of the bearing is running at its slowest.

I understand the quotes about engine revs, but honestly do many people hit 6000+ during a normal run out with the buggies? If they
do regularly then the failure of this part of their charging system should be accepted and just maintained as time passes.
Bearings now have some amazing properties, mostly due to modern machining abilities and last a long time, but in this one area
on serpentine systems, they are pushed to their limits very quickly.

Just make the modifications, look after it all with maintenance and you will see many happy miles knowing that the design and setup
you now have is up to the job.

Bearings dont last forever, so look after them

Peter

Was thinking about my previous post and cam belt tensioners then renembering most crankshaft gear pulleys are only 75 to 100 mm diameter so pulley wise it would need to be the serpentine air con/alternator belt tensioners.as you say Peter the bigger diameter the bearing the better so it would be possible to use a bearing fitted with an outer casing for the belt to run on slowing the bearing rpm down.

Peter I am the anomaly as I regularly use the 6500 but my drive gear is approx 75mm dia.

Peter I am the anomaly as I regularly use the 6500 but my drive gear is approx 75mm dia

Might have known it would be you 

You are quite right about the bearing in a sleeve and the sleeve slowing the bearing down, but why not
just have a large bearing (at least as big diameter wise as the sleeve) and do away with the sleeve altogether,
the bearing will be revolving even slower and you will have got rid of a completely unnecessary part, allowing you
to experiment a bit with larger bearing diameters as time goes by...

Peter 

There is a spreadsheet on here somewhere that calculates the revs the bearing will be doing

Worth a look

On a phone so hard to find the link

I hope people sort this out, its an on going issue and one that can be fixed.

Just me, but I wouldnt worry toooo much about charts, get the largest bearings you can
that accommodate the adjustments required, belt length etc and just have a centre
shaft made to mount them on.

And remember, 'deep groove bearings' are the starting point

Good luck with it Andrew 

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Thanks folks.


Am still waiting on the final parts with Gordon (Roadrunner    )


I think this could be one of my first videos to discuss and show the solution. Oh I should point out that I believe the the BMD serpentine system I inherited with this buggy was one of the first ones and I understand they have improved the bearings on the later models

Are there no O.E.M. belt tensioners from a production vehicle that you could use instead?

Most companies will have done the production research already, and you seldom hear of tensioner failure on a modern car   

The drive pulley on the modern cars with tensioners are much smaller so the belt travels slower.

On my Ducato camper the bottom pulley is quite a size so they do not use tensioners on both belts but the kit comes with ally ramps to feed the correct length belt over the pulley fences without damage, you can't get them off without cutting though..

The drive pulley on the modern cars with tensioners are much smaller so the belt travels slower.

Disagree - Subaru drive wheel is quite a size, and the engine revs a lot higher

The tensioner I have just removed is 70mm across - any use as an experimental donor for anyone?