Drive belt for a 90 amp alternator

[Becky]

We (unwisely in my opinion) fitted a 90 amp alternator to our Thorneycroft 35 hp engine. This alternator was described to us as the largest one can have driven by one drive belt. Well, the belt stretches as soon as it is tightened, and just cannot deliver enough grip to spin the alternator when there is a high load. We just get the screaming noise as it slips, and of course, the rev counter doesn't record properly.

Now, I might be blonde, but daft I am not. I KNOW that the belt will fail at the most inopportune moment, and to replace it is MOST awkward. It is inside fo the raw water belt, so that would have to come off first, which entails emptying the cockpit locker, removing the panel to expose the port side of the engine etc. (you know what I mean). So, I asked ASAP Supplies for an alternative way of dealing with this problem. They sent me a belt made up of three layers of fibre tabs, which overlap and are held together by three metal through-tags for each segment. Rather like the emergency belts you can get, but possibly stronger. They sent two of these, of different widths to allow for different pulley sizes, neither of which we have tried yet. They look to 'emergency-like' for to my mind.

My preferred cure would be to replace the original alternator, which with our Adverc controller should provide enough power.

The pulleys do not look wide enough to take a much bigger belt, and would be very difficult to change.

So, what do you guys suggest I/we should do? /forums/images/graemlins/confused.gif

 

[cliff]

This stuff? Details here

Keep the 90A alternator and fit either the above or a decent "V" belt. Do keep a length of the above incase the V belt breaks - easy to fit and lasts a long time.

Alternative, as you probably fitted a new belt try rosining the belt and pulleys to reduce the slippage.
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“Artificial intelligence is no match for natural stupidity”
Skype id:cliffillupo

 

[Becky]

Yes Cliff, that is exactly the stuff. Is it any good? Have you experienceof these belts? In fact,has anyone out there got experience of using these belts? Please tell me what you think of them.
Rosin..hadn't thought of that. Could be a very good idea. Thanks Cliff

 

[dickh]

You should go to a distributor of Vee belts, Braing Services Ltd or WYKO or any decent local drive or bearing specialist, take the original belt along and ask for a "GATES COGGED RAW EDGE BELT". These take much more power than standard vee belts, Gates in my opinion are the best but there are other manufacturers. Get two as even they won't last a long time with that sort of power.
The belt sizes obtainable are "Z" "A" & "B", the first Vee belts, then came SPZ, SPA & SPB, transmit more power, then came the Cogged Raw Edge belts in the three sizes, Z, A & B. Keep the linked belts as an emergency backup. Another alternative is to fit a larger section belt or TWO belts of the origuinal size - but that would require new pulleys etc etc.
From memory the alternator belt on my T90 is an SPZ 1060 Cogged Raw Edge by Godyear(but it could be one size shorter as it hasn't got much adjustment left)

 

[Piddy]

I use a cogged belt from BSL in Farlington to drive my 70A alternator with a Sterling regulator on a Thorneycroft 35hp the same as yours. No problems although I do check the belt regularly and change it most winters.
It does deliver 60 - 70 Amps for long periods according to the ammeter I have in line. I was lectured that this could cause inefficiencies and is a potential problem but it has been fitted 5 years clocking 100-150 hours per year and hasn't given any problems - yet!

 

[Salty John]

Agree with dickh. Your 90 amp alternator is borderline for driving with a single belt, but still OK. I had a 100 amp alternator on my Perkins 4-108 for many years and it worked fine, but I attended to maintenance and I used the best Gates belts. To make tensioning the belt easier you may want to consider replacing the slotted tensioning arm with a turnbuckle if it will fit in your arrangement. This allows you to tension accurately and avoids the tension being lost if the conventional nut and slotted arm isn't man enough for the job.

 

[cliff]

Yes I have used the WYKO belts as above - no problems even after prolonged use under heavy load >1500hrs transmitting 4hp driving a compressor and also a largish multi-blade circular saw.

If you follow the link and go to the home page of the site you can navigate to raw edge belts if that is what you are looking for. IMHO a good choice rather than "automotive belts".

Rosin on the belt and pulleys is an "old" trick used to help bed in new belts and maintain friction and give old worn belts (slipping) a slightly longer lease of life.
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“Artificial intelligence is no match for natural stupidity”
Skype id:cliffillupo

 

[fishermantwo]

Use a quality Gates belt and some belt spray if you need it to dress the belt. Avoid using the clip belt above in the photo. These are ok as an emergency but are noisy, if you have alloy pullys they will wear very quickly. Go to a specialist and spend the big bucks on a decent belt, you wont regret it.

 

[Avocet]

I don't know if your installation lends itself to this but have you considered fitting an additiona (spring loaded) idler pulley to increase the amount of "wrap" round the pulley? I assume it will be skidding on the smaller pulley (i.e. the alternator one). so maybe if you can get it to be in contact with a bit more of the pulley it might help.

Failing that, I'm currently using a "toothed" belt on my alternator (like a car's timing belt). I did this originally because I was fed up with all the rubber dust in the engine bay but if you can change the pulleys for toothed ones, (don't know how realistic this is!) you might find it will work. I got my stuff from Bearing Services, Maplins, RS and HUCO, if any of that helps!

 

[andyball]

[ QUOTE ]
belt made up of three layers of fibre tabs, which overlap and are held together by three metal through-tags for each segment

[/ QUOTE ]

Those sound more like fenner nuTlink or superTlink than the powertwist+ on wyko's site

 

[oldsaltoz]

G'day Rebecca,

Some years ago I had a 250 amp oil cooled Motorola alternator fitted to some heavy earth moving equipment to provide power for flood lighting.

It had a double belt set up, after shredding several sets of belts (some only lasted 2 hours) from several manufacturers I installed 2 Gates belts, they were still on the machine 4 years later when we sold it.

Needles to say I now own several gates belts, fitted to all our vehicles, compressors and anything else that breaks an original.

And, No, I have no connection to Gates.

Avagoodweekend......

 

[William_H]

With some light aircraft you have to remove the propeller to replace the alternator belt. A big job. So a spare belt is always fitted behind the prop and wired away where it will do no harm. Obviously if a belt breaks you can easily pull out the wreckage and if you have a spare almost in place in terms of getting past other belts and drives it saves a lot of trouble. it may be a useful idea. olewill

 

[Ships_Cat]

I suspect that the advice that a single belt is adequate is likely correct but I have not checked. Also, your comment that the belt stretches as soon as tightened indicates an inferior belt if I interpret correctly.

On our own 105A alternator we have 2 A section belts and they are very understressed (don't even need adjusting after installing new belts) and I suspect that one would be adequate.

Also, recently, on a new build I was managing, the 2 off 24 volt 150 A alternators (so require more than several times the power as yours to drive) were driven by a single vee belt (but a B section, not A, if I recall correctly). I actually brought it up as a check point with the yard building the boat but their engineers maintained it was correctly selected as indeed they proved to be so in service (they had good wraps on the pulleys though).

As Oldsaltoz says Gates belts are good and while there may be others that may also be ok, Gates has a good following professionally because of their reliability. There are many inferior belts around that will throw dust, stretch, etc (including the ones that come on new engines) even when used within their ratings.

John