Beta 43 and Travelpower caution

[Bobbybass]

This is from my own recent experience, and discovery that it is more widespread.

 

It is really my own 'theory', but I am posting it here as a few minutes checking may save you a lot of trouble and expense.

 

Last year, while on the Thames, my engine started to make a nasty noise.

After a while I found the cause was that the whole pulley assembly...alternator pulley and Travelpower pulley, was loose and rocking.

 

If you have never examined this...let me describe the setup :

 

On the end of the crankshaft is a taper...and the iron alternator pulley fits onto this with a key...and is held with a 46mm nut. Into the recess on the iron pulley is fitted a steel insert with a shaft attached and this then has the huge...(size wise and weight...to make a flywheel effect) Travelpower drive pulley. The Travelpower pulley is also on a taper that allows it to be moved to align the belt properly. That means that everything 'hangs' on the one 46mm crankshaft nut...not forgetting that..apart from the weight....there is the stress of the drive belts.

 

In my case the nut was loose...and I had to remove the Travelpower system to tighten it all up..and then limp home.

 

At my home marina..my neighbour told me he had this problem when his engine wasn't very old...in his case...the nut had been drilled and a roll pin inserted (carried out by Beta)

He told me that it had been loose and worn a 'step' into the crankshaft...so bad that Beta were forced to pay for a short engine and engineers time.

It had sheered the roll pin.

I have found others that have had this problem...so it is not unique.

 

Talking to Beta...they said that they had tried all sorts of things to secure the nut...lock washers...drilling..and even welding !..but it still came loose..

 

I have just put a brand new alternator pulley...nut assembly onto my engine..and then thought I had seen the probelm. My new pulley was hellish tight...even having heated it...and I tapped it for ages...but although tight..it rocked...

This is due to the crankshaft taper.

Eventually I had it down far enough to use the 46mm nut to pull it down...tapped it...tightened etc...and then eventually 110lb/ft torque...(loads of Locktight used )

I drilled the 46mm nut...BUT threaded it and used a 3mm alan headed screw...to lock it.

This is because..every year I will remove it and check the torque of the nut.

 

It 'occurs' to me (only my opinion) that the main problem is not the nut..it is the taper assembly.

Although my pulley is torqued down to 110ft/lb..that is only the front edge where it bites the taper.

The outer edge is going to be a lot less...and with the huge hanging Travelpower assembly..it will probably experience a sort of 'rocking stress'...which will eventually cut the front edge of the crankshaft..(like my neighbours had) ...and wear the alternator pulley. The 46mm nut will then give the appearance that it has come loose.

 

I would suggest a good thing to do would be to include a 'pulley check' into your regular maintenance. Maybe just get hold of the edge of the outer pulley and check it for rocking movement.

I 'think' it would probably rock and do damage for ages before you realise it.

 

I have now done away with the huge heavy Travelpower pulley and replaced it with a special aluminium one (I know I lose some flywheel effect). I have also moved it a lot closer to the alternator pulley..and made the Travelpower alternator adjustable to line up the belt. This puts a lot less stress on the 46mm nut and taper.

 

This is based on my experience...and is only my 'assumption'.

 

Hope it saves you a problem.

 

 

 

 

 

 

 

[The Bagdad Boatman (waits)]

With taper shafts, one of the recomended ways is to use grinding paste to bed the pulley and shaft taper.

[by'eck]

Interesting story which in essence suggests the crankshaft and pulley tapers do not match.

 

I feel obliged to ask why Beta, aware of this problem, don't supply the correct pulley. Maybe a case for some legal encouragement.

[Chris Pink]

Indeed there is no theoretical reason why this power cannot be transmitted through a taper fit pulley. It is bad engineering.

[bigste]

As an engineer I'd be more concerned as to why it is a common problem and strongly suspect the pulley needs balancing. I've seen this before on unbalanced flywheels and nothing can stop them working loose except balancing. Balancing is a specialist equipment job but can be done by a clever minded person. The way I have done it is to have a dummy piece of shaft that fits the flywheel and only an inch or two long. It needs to be drilled on a lathe to take some fishing line. You then let it dangle to see if it is balanced. If it needs balancing you use something like a 1/4" drill and put various depth holes around the edge until it is balanced. It's a bit old fashioned but it does work. The most vital bit is not to have the drilled fishing line hole sloppy, the line needs to be a good sliding fit. You'd be surprised how much a perfect looking flywheel can be out of balance and it is common to have to drill 3 holes a quarter deep to get the balance right.