24v alt set-up for J3???

[NorthwichTrader]

Any ideas on the best alternator and belt set-up for a 24v system? I'm going to make the entire boat 24v, so something that's powerful enough to charge the whole system when cruising (I guess)?

We're going to be marina-based for a while, but want to plan our set-up for a final off-grid existence, if that information has any bearing??

[OldGoat]

For that sort of engine, you need a girt big slow revving alternator - something like those fitted to Gardners on buses. I have a CAV 100amp beast lurking around somewhere. Otherwise a big Prestolite at 175 amps would do. Obsolescent bus / truck alternators come up on eBay from time to time, with the advantage of being rugged. - better value than over driven car type units.

 

I recall a thread on here somewhere where a multi-V flat belt was used from the flywheel to drive the alternator.

 

Best if any engine 'lectrics are 24V or you'll have the problem of separate batteries and another alternator.

 

Good enough for a start?

 

[OldGoat]

Can't edit previous post, but I have a couple of these on my boat:-

http://www.ebay.co.uk/itm/NEW-ALTERNATOR-LEECE-NEVILLE-110AMP-24VOLT-CATERPILLAR-MARINE-HINGE-MOUNT-TYPE-/370860072105?pt=UK_CarsParts_Vehicles_BoatEquipment_Accessories_SM&hash=item5658fb9ca9#ht_2934wt_1076

 

Big solid lumps 70amps @ 24V = 140 amps for normal (12V) folk so that's enough well. Not particularly slow running, but IIRC give good power at 3000 rpm (automotive types nee nearly twice that speed and aren't very robust). These were designed for buses - I think Dennis fitted them.

 

Good price too.

There's a power curve available on the Leece Neville site for their equivalent unit.

 

 

Bother, belay that link; this one:-

 

http://www.ebay.co.uk/itm/NEW-ALTERNATOR-24V-VOLT-DELCO-REMY-22SI-TYPE-FOR-CATERPILLAR-CUMMINS-J1-MOUNT-/221184092770?pt=UK_BOI_Industrial_Tools_Construction_Tools_ET&hash=item337f996a62#ht_999wt_838

 

(Blurry IE won't let me preview the post, so hope above is OK)

 

 

[BEngo]

Another vote for multi-v belts. Avoid the automotive size (K) because the available lengths are limited and they are harder to find- J size or L size with rib numbers to suit the power you need are the ones to go for. However if you run one on the outside of the flywheel (presumably the 'small' version as opposed to the diesel-start one), without grooves, which is OK, the trick is either to use a low-speed alternator with a biggish pulley or a jockey pulley to get sufficient belt-wrap on the alternator. The minimum alternator size will need to be determined on the basis of your battery bank size and what sort of electrical consumption you expect. Too big is not an issue, but too small will be.

 

Alignment is crucial- the alternator axis must be parallel to the crankshaft axis and the pulley in line with any engine pulley. A multi-v belt will self align on the flywheel though parallel is still vital

 

If you have the flywheel pan fitted the alternator mounting will need to be quite high to give belt clearance.

 

Alternatively you can mount a pulley to the flywheel bolts (6in PCD) but this will perforce be smaller. If using V or wedge belts you will probably need a twin-belt set-up for anything more than about a 50A alternator. For a 12V alternator you can go to 70 or even 90A on one belt.

 

Sitting there at low loads just charging batteries will not be an ideal existence for a J3, so think about solar and/or a generator to do the lower-current absorption charging and equalisation charges.

 

Starter motors are not a problem in 24v- A CAV BS5 24 P101 should be right for a normal rotation engine, with a bronze starter pinion for a cast iron flywheel. The gap between the front pinion face and the rear of the flywheel should be 9/64in IIRC.

 

N

[NorthwichTrader]

Many thanks, so what do we all think of this one, then (Thanks, Old Goat)? As suggested above?

 

ANEW ALTERNATOR 24V VOLT DELCO REMY 22SI TYPE FOR CATERPILLAR, CUMMINS J1 MOUNT

 

A good starting point?

[OldGoat]

Nobody else?

Perhaps the requirements are too specialist?

 

Here's another one Leece Neville / Prestolite 8SC3009ZA. Same J mount (large frame alternator) as the 22SI. nearly twice the output but 4 times the price on ebay - or even more if you buy from a distributor.

That's why I suggested the 22SI. All the other 24V ones I've seen listed are less than half the output for similar money.

 

At £119 it's excellent value - so U don't expect it'll be around for long.

 

Methinks your problem is not so much 24V or what alternator, but how to mount it and how to drive it on your engine, especially as it's a slow revving engine. At full chat the 22SI will (in theory) absorb 3bhp and I don't know how an unrestrained flat belt will deal with that.

 

I'm going away now - don't want to push too many ideas without confirmation / denial from folks who've done it on that type of engine.

 

(all info above came from a quick Google and eBay which are often reasonable indications of what's out there. Charts and diagrams also)

 

[BEngo]

I can't be specific about the suitability of any alternator, because I have no idea of what you need to put back into the batteries. I doubt the one above will be too small unless you are a real power hog with more batteries than a U-boat but, if you are content that it will supply your needs then as OG says the next step is to work out how to mount it and how to drive it. If you want to check your needs do a power audit- there is guidance on Tony Brooks' website as well as in other places.

 

There is plenty of guidance out there on the web, covering belt sections, speeds and required wrap for any of multiple V-belts, Multiple wedge belts and multi-rib belts. There are loads of variables- Power transmitted, pulley sizes, belt sizes, belt width ad nauseam. To get a start you have to have worked out some physical possibilities:

 

What do you want to drive off? Pulley ( how big, how wide can it be) or flywheel rim?

 

How can you mount an alternator and tension the belt(s)- some ( big V, big wedge and multi-rib) need positive tension devices others can get away with just a big pull and clamp in place. Positive tensioning is always better.

 

What is the centre-to centre distance between the drive and the alternator ? ( belt wrap possibilities)

 

What size pulley can you get on the alternator? ( belt wrap possibilities) Look at diameter and width

 

What is the ideal alternator rpm -when does it best make power?

What will be the cruising/charging engine rpm (These two give you a target drive ratio)

 

What is the max safe alternator rpm (This gives you the max ratio )

 

What is the alternator power input- allow for some significant losses for the fan and for efficiency. The alternator charts might give you this.

 

When you have all these wade into a set of belt charts and see if the answers that come out are ones you like. If not go back to the physical arrangements and then try again. If you want a hand PM me as I have most belt charts hiding somewhere.

 

 

When you have the drive sorted you can worry about the cables!

 

N

[NorthwichTrader]

I'll get my coat, chaps!

Oh, boy, maybe something for another day? I'm going to have an electric-tent set-up in the meantime, so can always charge the batteries manually!

If you've personally got something that will do the job, Old Groats, please PM me!

What a subject! Blast, was hoping to nail it without a grey-matter overdose!

[BEngo]

It's easy enough to bung something on, and at low powers it will work fine. One you start to ask a big alternator for most of its power output (and why have a big one if you don't need it?) then you'd better be able to turn the alternator fast enough and feed it the power it needs. Get various bits wrong and either belt-life will be short, alternator bearing and diode life will be short or it won't charge the batteries effectively. Whichever way it can be a world of hurt in the wallet.

 

Fortunately it's not that hard to sort out, there a just a lot of variables.

 

 

N

[OldGoat]

It's easy enough to bung something on, and at low powers it will work fine. One you start to ask a big alternator for most of its power output (and why have a big one if you don't need it?) then you'd better be able to turn the alternator fast enough and feed it the power it needs. Get various bits wrong and either belt-life will be short, alternator bearing and diode life will be short or it won't charge the batteries effectively. Whichever way it can be a world of hurt in the wallet.

 

Fortunately it's not that hard to sort out, there a just a lot of variables.

 

 

N

 

That's why I suggested a large (potentially) high output commercial vehicle alternator. Run them well below their design limit (that's why you need the output curves) and they should last. My 175 amp-er is 15 years old and still works. Commercial vehicle types are intended to be run all day at or near their rated output.

 

I do agree about the bearing problems - but ONLY for the tweaked Balmar types which run at very high speeds to get the output; they run at about 10,000 rpm.

 

The large unit used twin 'A' section belts and the smaller 70 amp ones run on 6 row K section flat belts

[BEngo]

I agree that a CV alternator, properly installed will run for a very long time. If NT can get one and put it on his J3 I doubt that a good job will need much apart from routine servicing for the next 10 years. And then it will be because the belt is aged.

 

Modern CV's and cars do have the advantage that the alternator, and a lot of other belt-driven bits are designed onto the engine at the early stage of engine design. In a boat, with an old engine which was pretty well designed pre-electrics life is a different mollusc. An alternator set-up has to cope with the existing engine and the limitations of it's installation space with all the possible compromises at least half-fixed.

 

 

Bearing problems for any alternator arise in a poorly designed/built set-up if there is not enough belt-wrap, so the set-up has to be over tensioned to stop belt slip. That in turn overloads the front bearing. It will also eat belts, either because they slip or because they are too tight.

 

Modern belts are designed to help overcome the wrap problem- look at what a modern car or CV belt drives, and the way the belt snakes around to get to and wrap properly on all those pulleys. Not for nowt are they called serpentine belts. They still are no good at misalignment tho'.

 

N

[NorthwichTrader]

Thanks everyone, once again, I will come back to you on this one!

I'm wondering whether a floor mounted unit powered by 2 v belts would do the trick, I've got a fair clearance ahead of the flywheel?

When bolting to the flywheel, are we talking of tapped holes into the bolt heads, or fitting something beneath the bolts?

[BEngo]

Thanks everyone, once again, I will come back to you on this one!

I'm wondering whether a floor mounted unit powered by 2 v belts would do the trick, I've got a fair clearance ahead of the flywheel?

When bolting to the flywheel, are we talking of tapped holes into the bolt heads, or fitting something beneath the bolts?

 

 

My A127's are both on mountings welded to the floor. It was bloody fiddly to get them welded on in exactly the right place and with the alternators parallel to the crankshaft. I should probably have devised a more flexible mounting so as to be able to line it up after the welding.

 

I'd still suggest you use a multi-V belt rather than double V belts. Multi-V need much less pulley wrap on the alternator and will go round smaller pulleys.

 

The original close tolerance Kelvin flywheel bolts were tapped in the bolt heads so that you could A) fit a pulley and B.) pull the bolts out if needed. If you have replaced them with modern ones then you can either fit longer ones through a new pulley or tap the new ones- it's easiest to do it in a lathe so the holes are easily centred in the bolt and the heads are then very lightly faced square to give a good seat for the pulley. If you fit a new pulley against the flywheel (as opposed to onto the bolts) remember that there is a recess in the forward flywheel face so the grooves need to be positioned with an offset so the belt clears the flywheel.

 

N