Mercedes Engine - ST Generator Mounting

[WStayton]

mike90045:

  Ok, let see . . . I'll only need a couple of four shive(sp?) pulleys for the engine and the generator with four each 5/8" or 3/4" belts on each of them to transmit the 32 + HP required to drive the generator-head  and, oh, by the way, you are guaranteed to have one of the belts fail at the worst possible moment (think:  middle of a January  snow storm) and then wad the other three, and probably the idler, which you will need to keep them tight, all up in a neat little, un-unscrewable package..... Hmmm, let me see, is this a good idea?  Not unless you are the original masochist! <grin>

  That is why I elected to put in a transmission that is gauranteed to handle the horsepower and has easily and usually not sudden onset failure modes - noisy bearings, etc., etc.

  Plus, I think (always dangerous) that four v-belts absorb more horsepower in their hold-down/on friction than the gear box does, even if I run it in 3rd gear.  Numbers that I  have seen, indicate that a highly loaded v-belt absorbs something like 15% of the input horsepower in friction - that's why you need so many for much horsepower, since they get pretty hot.  I am thinking that my transmission will absorb about 5% of the transmitted horsepower in fourth gear and about 10% in third gear.  I'm not real happy with the 10% but that will let the motor run at a more efficient rpm, so I will probably will only have a net loss of something like 7% - -10% for the gearbox and +3% for running nearer peak BSFC.  I can stand throwing 7% away, but 15% exceeds my ability to stomach the loss!  If I install v-belts I will not have the ability to operate in anything eqivalent of fourth gear and the loss will be three times what it would be with the engine producing 20 kW.

  I chewed on how to best hook the engine to the generator for quite a while and briefly considered v-belts, but discarded the idea for the reasons elucidated.

  I could also use a cogged belt such as many overhead camshafts run with today - this solution does have efficiencies that are somewhere between the 4th gear and 3rd gear efficiency of the transmission, but they again are less than 100% reliable - I frankly never understood how an engine designer could put one on an engine where a failure results in piston-valve interferance; its clearly a triumph of cost cutting over good engineering judgement!  Of course, when I worked at Ford, we always said that management would skin their grandmother's for $1.00 a unit cost reduction and a cogged belt saves something like $2.00 per engine over a steel chain if you count the attendant pulleys/gears.  Also cogged pulleys are something that is sort of hard to find just laying around in a bin at your hardware store, so they would probably have to be custom machined for this application - I'm pretty sure that would exceed the $100 cost of the transmission that I acquired - remember, I'm cheap!!  <grin>  A cogged belt would have power losses near what I will get with a transmission, in fact, maybe slightly better than I will get in 3rd gear, but, because of the failure during a snowstrom scenario, I discarded this idea, too.

  There is also the problem of having to align the engine and the generator with precision so that the belts, whether v or cogged, will run true.  Probably not as critical as alignment necessary for a Loivejoy coupler, but still not a trivial problem if you want to have as long a belt life as possible.

  I've considered belts and pulleys and thanx, but no thanx!!! <grin>

Crofter:

  So are you suggesting that I should "hot shoe" my engine and generator?  <grin>  Just kidding!!!

  I too have helped, at least, shoe a few horses, though they were my Dad's Clydesdales.  It was sort of like fitting a shoe to a wash tub their feet were so big! (Slight exaggeration!)  Though my Dad didn't believe in hot shoeing, so they had to all be rasped flat - and when you're shoeing an eight horse hitch, that's a lot of feet and even more rasping!  Most of them were pretty reasonable animals, but there were a couple of them that just LIVED to bight the living s$!t out of you if you gave them half a chance and when a 2,000 pound horse clamps his teeth on your a$$, it DOES smart!!!  Leaves VERY intersting bruises, BTW!!! <grin>

  Back to the problem at hand:  How about if I drilled the holes slightly oversized - say 0.250 - and then got everything in a position where the spacing was okay, except, maybe, for the last 0.025 shim here or there, and then poured the oversize hole full of epoxy, again tightening everything down until the epoxy hardened, and then did the last final shimming, again between the two large flat washers on top of the metal plate, so that the bottom washer would be bedded in the epoxy?  Maybe undertorquing for the epoxy cure so that there would be a very slight excess to compress at the final tightening?  I think that a 0.250 oversized hole would leave enough room for me to introduce a hypodermic needle to make sure that I got the epoxy all the way to the bottom of the 4.50" deep hole.  I would want to do this on a cold day, so that I would have lots of time to get everything lined up and semi-torqued, before the epoxy set up. 

What do you think, would this work?

Regardz,

Wayne Stayton