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BMC 2.2 Dynamo to Alternator


croftie

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Current boat is a Dutch steel "Pedro" style cruiser (saloon, wheelhouse, rear cabin) which I am slowly updating. 10m with a BMC 2.2 engine that is still running a dynamo....... don’t laugh - 25amp to 30amp? Want to upgrade to alternator for obvious reasons and can see 3 options. I think the type fitted to the alternator equipped engines was the Lucas 11ac

 

Option1. Find some 2.2 alternator brackets and locate an 11AC alternator. Rough search on net shows cost of 11AC to be around £200. Charge increased to 70amp

 

Option2. There is a direct replacement “'Dynator' Alternators” that would cost around £300 - £400. Have yet to check dynamo part no to see which would be the correct replacement. Charge increased to 65amp

https://www.autoelectricsupplies.co.uk/product_list/197

 

Option3. Make up my own brackets (capable of doing) and fit a more modern std alternator such as A127 type alternator, cost around £100. Charge increased to around 75amp

 

Option1 is easy if I can find brackets but 11ac is I think an old alt and could be difficult to obtain in future (prob would not be my problem)

Option2 fitting simple but long term very similar to above regards future problems.

Option3 more problematic fit but cannot see downsides.

 

No problems skill wise doing the necessary fitting, wiring, new ammeter etc but would be interested in the forums views on the above. All around similar output. Usually in marina with shore power with the odd weekend away so mainly more an update than a necessity. Currently 280amp domestic bank + starter battery.

 

Also anyone have the suitable brackets for option1 should I decide to go that way.

 

 

 

 

 

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1 hour ago, Bee said:

In my experience alternators have a long life, so the local car breakers looks like a good place to start.

But don't choose anything too modern or it will be an ECU regulated beast. You need a bog standard internally regulated alternator like a 127. 

1 hour ago, RLWP said:

I may have a set of BMC 2.2 alternator brackets, most likely to take a more modern alternator than the 11AC

Richard

Sounds like a great solution :)

So basically, option 3. 

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As said fit something like a Lucas A127 for well under £100 and deal with the brackets. Its been a long time but I THINK the front one mat be OK with a few washers for packing, the rear one definitely needs changing. The AC range is old so expensive and it requires an external regulator, relay and, depending upon the relay, a warning lamp control - all adding more potential failures.

Any A127 you buy will have at least twice the output of the alternator the main charging cable will need replacing and it is often easier to run a new warning lamp cable rather than making joints at the control box. If your control box is a two bobbin one you will need to join the A and A1 (from memory) cables and if its a 3 bobbin box then link the  two 9mm blades at one end (possibly marked B)

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Remember that you will need to increase the gearing ratio of the alternator as they need to spin a lot faster than a dynamo. That might mean fitting a larger engine pulley. If so and supplies are difficult then consider converting to Poly-V pulleys and belt drive. Not cheap.

I make the suggestion because the pulleys fitted on the link you supplied look about as small as you can go to get a decent 'wrap'

A cheaper but less long lived solution is to use a larger engine pulley and cogged belts - here -

https://www.bearingboys.co.uk/Cogged-Belts-3831-c

 

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I think our 2.2s used a fairly large cast iron pulley and fitting the alternator with the smallest available pulley (not the one that may come with the alternator) plus using a notched/toothed belt seemed to work all right.

I doubt a standard A127 needs anything more than a quality V belt.

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12 minutes ago, Tony Brooks said:

I think our 2.2s used a fairly large cast iron pulley and fitting the alternator with the smallest available pulley (not the one that may come with the alternator) plus using a notched/toothed belt seemed to work all right.

I doubt a standard A127 needs anything more than a quality V belt.

IME it depends on how small the alternator pulley is. Before I converted to Poly-V transmission, I had a 60mm alternator pulley and 10" main pulley (nothing like mixed standards...) and I found  that plain Fenner V belts barely lasted a season. I switched to BBs cogged variety and they lasted 4 seasons and more to come (but I replaced the engine. OK it was a much bigger alternator with twin row belts. However, you've much more experience that I, so I must bow to your superior knowledge......

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The standard A127 seem to come with about 70 amps as the maximum output and some a slow as 45 or 50 amps so a V belt shoudl be fine. I think we are both talking about same same type of belt,  with bits cut out so it wraps around small pulley better.

At one time, and there may still be, an alternator designated as an A127 was available with a  90 amp output but an A127 it was not. I think it was a re badged Bosch design. I would have reservations about driving that with a  single V belt.

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12 minutes ago, Tony Brooks said:

The standard A127 seem to come with about 70 amps as the maximum output and some a slow as 45 or 50 amps so a V belt shoudl be fine. I think we are both talking about same same type of belt,  with bits cut out so it wraps around small pulley better.

At one time, and there may still be, an alternator designated as an A127 was available with a  90 amp output but an A127 it was not. I think it was a re badged Bosch design. I would have reservations about driving that with a  single V belt.

That's the one! Bearing boys call it  cogged belt, I got taken to task by calling it a toothed belt.... 

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I think all you need is a longer bolt and that distance piece if front of the rear bracket. The bracket itself looks very like the dynamo one to me.

Not trying to Richard out of a sale but I would be looking for a scrap of steel pipe and hacksaw if it was mine. The length does not need to be accurate becasue the bush in the rear alternator mount slides in and out of the end bracket.

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  • 1 month later...

Just a follow up,

My dynamo was mounted different to Richard’s setup. Instead of the front mounting being on the front engine mount it was on the top outer timing case bolt so I decided to use this mounting point together with the original rear mount bracket. In Richard’s pic it shows the rear extension using a length of tube. This I wasn’t too keen on as it would be possible for the rear alt sliding bush to pull through the rear mount and simply slide into the tube (if you look at the pics I’m sure you will understand).

So after a quick measure I got hold of a piece of 20mm dia aluminium bar with an 8mm clearance hole the “correct length” to take up the difference. Bolted the new alt at the front end (pulleys nice in line) and slackened the two nuts holding the rear mounting bracket to block. Placed the new aluminium spacer and adjusted the sliding bush in the alt rear mount, tightened up the rear mount to alt. Then tightened up the 2 nuts holding rear bracket to block. This way no strain on the front/rear alt mountings.

Little unsure of the alternator output etc I bought from Richard I decided to go for a new 75amp one from ATP (a company I have used before). New cogged belt and new 16mm2 cable to 80-0-80 ammeter so bypassing all the old dynamo wiring.

Now to test…..  I am on shore power so the bats (new this season) are well up toward 100% SOC (sorry no SG to verify....  :giggles:) Engine started, warning lamp out and low amperage in. All good so far. Switch off engine switch on inverter and run a 1kw fire for a minute or two, (100amp draw) restart engine and even at tick over a nice healthy charge going in. Increase revs to ~2000 and ammeter showing 70+ amps.

All in all very happy with the end result.

  • Happy 1
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