Serpentine belt driven high-output alternator on Ford Lehman SP135

[svenkei]

Hello all,

I would like to extend my Ford Lehman SP135 (2725E) with a 250A 12V high output alternator. At normal cruising speeds that would yield about 150 to 180A of current flowing to the Lithium bank. The electrical system is setup to work with these and higher currents.

The alternator is serpentine belt driven and I have an AltMount pulley conversion kit for my engine type. Problem is that my crankshaft pulley (or balancer I believe the correct word is, not an expert) is not the stock type so the conversion kit won't fit. The crankshaft pulley is 2mm to wide for the slip-over serpentine conversion pulley to fit.

In addition there are a few other peripherals that need to stay installed: a V-belt driven hydraulic pump for the anchor windlass and the current 60A V-belt driven alternator that I would like to keep as backup.

I am now breaking my head on what would be the best way to install all of this and also ensure that it is a solid setup capable of dealing with all the forces with minimal wear on the parts. I am looking for advice on the following options or alternatives:

1) Replace current crankshaft pulley with stock FP6091909 double V-belt balancer and attach the slip-over conversion kit. That will make the crankshaft pulley, the coolant pump and the high-output alternator all serpentine driven. This is not recommended by American Diesel because of the supposedly higher failure rate of the coolant pump bearings but it is the way the conversion kit is designed to work. In addition there would need to be mounted a second double V-belt pulley on the front of the slip-over pulley to drive the hydraulic pump and second alternator. This is an expensive option all together.

2) Do the same as option 1 but machine down 2mm of the current crankshaft pulleys to make the slip-over fit.

3) Abandon the idea of having the coolant pump and primary alternator serpentine belt driven. Keep the double V-belt crankshaft pulley/balancer that drives the current setup and use it as base to bolt the slip-over serpentine adaptor to the opposite way around with 6 slightly longer bolts. (see image for test fit). Now the serpentine adaptor pulley will directly drive the high output alternator. The latter will need to be fitted on a custom mount as it is placed somewhat further out from the engine that with options 1 or 2. But is this setup feasible as in strong enough and not imposing high wear on the engine?

I appreciate your thoughts on these options or alternatives perhaps. I attached images on the envisioned orientation of all the belts (V-belts in the image still), the serpentine adaptor (black) and current crankshaft pulleys.

[MWGDVC]

Svenkei,
As I am not familiar with your particular engine, these comments will be of a more general nature.
Most of our marine engines are adapted from industrial applications, where generally the electrical loads are confined to recharging a single battery, and feeding small loads such as a few lights.
The majority of the work is drawn from the large diameter, short rear of the crankshaft.
Your 3000W alternator load wasn’t considered in the design of most of these engines. Assuming 100% efficiency (it wont be) you are drawing a nearly 4 horsepower load from the front of the crankshaft.
Generally the crankshaft nose is not of a terribly large diameter, and there is usually a significantly long section of unsupported shaft at this end. Consider the location of the main bearing, behind timing gears, seals, pulleys. The closer the load to this bearing, the less stress on the assembly. An option might be to oppose or balance the load with another load by using a second alternator 180 degrees apart, or perhaps the hydraulic pump you referenced.
I have seen 2 snapped crankshafts in automotive applications, due to adding pulley driven accessories not originally intended in the design. Both instances placed a significant load outboard of the original factory pulleys. Whether the failures were due to load, or a vibration leading to metal fatigue, I cannot say.
I am not trying to dissuade you from this modification, merely pointing out a potential pitfall.

[tkeithlu]

That's a added 4+ horsepower from your engine, which you likely can afford, but like the add-on engineers, I'm concerned for the lateral load added to the bearings. That's particularly the case in option #3, where the arm between the crankshaft bearing and the belt has been roughly doubled. I would suggest review of the question whether you need another 250 amps, or might better just use a somewhat heavier alternator in the original position. Then you could keep the 60 amp (which is rather small) as your backup.

I am a bit of a worry-wart about after-market engineering. The entire front of the engine was designed with particular loads in mind. Over-engineering it would have raised production costs and weight. The designer included a margin for things like bearings, most conventionally 2.5 times expected load, but how much of that are you already using up with the hydraulic pump?

I'm dealing with a parallel case at present - the retracting ramp on a handicapped friend's van has resulted in premature failure of the sliding door. At Least she can pull over and park when the door falls off. Twice this week...

[mvweebles]

These engines routinely had loads bolted to them, including aircon compressors and such. I personally wouldn't worry about side loading. Of all the reasons diesels die or are killed, side loading simply isn't on the radar.

I'd go with a serpentine belt and call it good. In the US, this type of kit is available for the 4-cylinder Perkins 4.236. Certainly a Ford Lehman 120/135 is a no brainer (though kit is not readily available.

You may want to ping the folks on TrawlerForum. Ford Lehman's are probably the most common engine amongst trawler owners. Ton of good info available including folks who've done what you're considering.

[Bowdrie]

The normal stock devices like the raw-water pump/coolant pump/low output alternator, all operate with relatively small side loading.
Refrigeration compressors can easily compete with a high-output alternator for power requirements and side loading.
I have one beef with serpentine systems, they are still a high tension friction drive, and when one belt is used for all things the coolant and raw-water pumps and the stock alternator are always subjected to greater than needed side loads and generated heat.
Many alternator failures can be traced to the heat generated at the pulley which goes right into the front bearing.
If you have the room to spare, an off-engine drive using a "Gilmer" belt gives positive power transmission with much less side loading and far less heat.
The stock pumps/alternator operate with little tension/heat, and all is well.

[Wotname]

Like others, I can't provide specific advice but offer some general advice.

These Ford engines were designed back in the day and were bullet proof. They were used in all sorts of commercial applications (trucks, buses, tractors, industrial applications etc).

The Lehmann marine version has been around forever and many are fitted with high output (bus) alternators. The only question is the best pulley / belt to drive the alternator. You may be restricted by existing space constraints in the engine room.

There is nothing that American Diesel does not know about the Ford Lehmann (they have a long history with these engines), I would take their advice as gospel.

Me - I like your #3 option

[svenkei]

Thanks all for your opinion and advice, that is much appreciated.

The Ford engine is indeed a reliable strong workhorse. It has served on my ship since 1987 and I hope it will remain in service for some years to come. The previous owner did install quite some after market peripherals including the mentioned refrigerator compressor. I removed that one as I have no need for it but is shows that the engine has powered two alternators, a refrigerator compressor and a hydraulic pump without problems for as far as I can tell.

I do have quite some space in my engine room and temperatures rarely exceed 40 degrees C. The high-capacity alternator is one with an external rectifier reducing alternator heating. I am not worried that much about temperature problems.

I mentioned having a different crankshaft pulley than the OEM one that is preventing the slip-over pulley from fitting. I can't tell what it is, no type information. But browsing on images it seems it is a pulley with an additional damper. That might be a deliberate after market install to power all of the peripherals. I might one to keep it, ruling out option 1.

I value the opinion of American Diesel allot so I am doubting a bit about option 2. I will definitely post my question on the Trawler forum that is a good tip.

[skipperpete]

I never liked the way the alternator was mounted on the Ford Lehman engines, the flat plate plate wasn’t very thick and the pinch bracket for the alternator foot made it hard to keep the angles right so that the belt had a reasonably long life. Does the new high output alternator go on on the same side as the original one or did the kit maker find a better place for the mounting bracket? I completely agree with the previous posts about the strength of the front of the crankshaft, it can take a lot of lateral load. I’m interested to see how well this works out, I’m sure it will be a success.

[donradcliffe]

Since the engine was used in tractors, you might ask American Diesel if some versions had a PTO.

[svenkei]

I had to look up what PTO means :-). But a quick browse did take me to a few links about power take-offs for this engine indeed mostly used for agricultural purposes. The PTO's are rather big though, I don't think I have room for them besides the question if it is needed. But for sure that would be a very sturdy solution.

[svenkei]

Originally Posted by skipperpete

I never liked the way the alternator was mounted on the Ford Lehman engines, the flat plate plate wasn’t very thick and the pinch bracket for the alternator foot made it hard to keep the angles right so that the belt had a reasonably long life. Does the new high output alternator go on on the same side as the original one or did the kit maker find a better place for the mounting bracket? I completely agree with the previous posts about the strength of the front of the crankshaft, it can take a lot of lateral load. I’m interested to see how well this works out, I’m sure it will be a success.

Thanks for that. If I would follow the recommended installation for the pulley conversion kit the high output would be installed in place of the stock alternator (option 1 or 2). That would fit although some strengthening of the mount might be a wise thing to do as you pointed out. If I would go for option 3 the alternator can be fitted on either side of the engine. There is space but in both cases a custom mounting bracket is really needed.