Generator head pulley

[KDB]

Looking for a serpentine pulley for use with a 6/1 1800 RPM gen head. 8.25-8.4 inch diameter or so. Any standard bush system (SK preferred). With or without a bushing (will need 42mm for my app). Able to ship to Texas address.

[38ac]

I machined exactly one of those pulleys when a serp drive was necessary or one would get thrown out of the cool club. If I priced making another one even at zero profit I would get laughed at.  Truth of the matter is the actual HP savings over a V belt drive is so neglegable that it cannot been determined except in a laboratory setting. Everything I have set up since that first one uses 2 A section belts, 8.5 OD 2 belt sheave which will have a pitch diameter of around 8.25 depending on manufacturer and engine speeds of 630 RPM or so.
Of course it is up to you how you spend your money but that whole serp belt deal was mostly an unnecessary and expensive fad. If you are dead set on saving a quart of fuel per year via tbe belt drive then go with a V belt pulley and instead of a standard belt purchase a box of A section link belt from Fenner Drives.

[KDB]

You may be correct but I'm not asking someone to machine me one. I could do that just down the street but like you said, it would be expensive. I know for a fact that there is many of what I describe in existence and there may be someone that has no use for one and would like to take the opportunity to get something for it rather than store it the rest of their lives. I have seen them for sale before for a price I was willing to pay but I didn't need one then. I also think that when you are starting with 6hp, it is worth while to make an attempt to get one when you plan to use it on a generator head. If I was pumping water or something I wouldn't worry about it but a couple hundred watts when your total is only in the 3.5K range to start is significant depending on your plans for the power.

[keith71]

I machined exactly one of those pulleys when a serp drive was necessary or one would get thrown out of the cool club. If I priced making another one even at zero profit I would get laughed at.  Truth of the matter is the actual HP savings over a V belt drive is so neglegable that it cannot been determined except in a laboratory setting. Everything I have set up since that first one uses 2 A section belts, 8.5 OD 2 belt sheave which will have a pitch diameter of around 8.25 depending on manufacturer and engine speeds of 630 RPM or so.
Of course it is up to you how you spend your money but that whole serp belt deal was mostly an unnecessary and expensive fad. If you are dead set on saving a quart of fuel per year via tbe belt drive then go with a V belt pulley and instead of a standard belt purchase a box of A section link belt from Fenner Drives.

   I agree 100% The serpentine belt "may" have a slight advantage vs the standard 2 A belt v pulley and I guess it looks cooler.. 2 qaulity A belts on a v pulley has been around for since the beginning. JMO.. And I realize this is not an answer to the op's original question.

[mike90045]

i had to "crown" the engine flywheel side, to keep the belt from wandering.  I used about 3 layers of 10mil plumbing tape.  Been working for years.  Wrap in the direction so the belt tightens the tape, or it will loosen it and throw it all off in a few minutes

[mobile_bob]

i would concur with the use of the v belt drive

the serpentine/microgroove belt really got into its own with the advent of front wheel drive cars, where the engine overall length needed to be as short as possible, and having one belt driving everything in one plane made for a more compact drive system and a shorter engine package.

for what we are doing i wouldn't recommend using one, unless you plan on driving something with the back side of the belt?

i did a lot of testing with the AA (hexagonal section) drive system, so that i could drive on both sides of the belt, and run the belt in a serpentine fashion,  in testing it was very hard to tell or prove that a microgroove belt would have made a significant improvement in efficiency.

maybe a half % improvement over a well designed v drive using quality pulleys and belts., and would have to see some solid proof before i would buy into a 1% improvement let alone something more.

i have built drive systems with both microgroove and v belts, the microgroove i chose because i wanted to drive the belt from the back side (over the r175 flywheel) and also 3 driven components using the grooved side (actually 2 driven, and 1 for the starter via electric clutch). this allowed for a compact system that was very easy to change out the belt on if needed.

the AA hexagonal section belt system was used to drive twin 555 alternators and an A/C compressor where i could use the back side on the drive pulley to keep from having a trapped system (engine was direct driving an st head). i can change out both belts with two 3/4 wrenches, and a 9/16" wrench in under 2 minutes and have it back up and running again.  for a drive system that is more complex than the typical 6/1-st5 a two minute belt change is acceptable to me.

add to that the over 180deg belt wrap on the twin 555's is hard to match.

point being, good quality v belts and quality pulley's can work really well.

thinking back, the microgroove belt and st pulley arrangement made a lot of sense when folks wanted a simple and efficient drive using the outer rim of the 6/1 flywheel which in the case of the indian clones didn't generally come with V groove?  that is iirc?  it worked out pretty well to buy one pulley for the st head and pickup a microgroove belt and just put it together.  with the need to step up from 650rpm to 1800rpm  it was cheaper to drive off the flywheel rather than purchase a rather large pulley to mount to the crank and also purchase a pulley for the st head.

i think that is how all that got started?

because it was love at first sight for me with the s195 changfa, i really never thought much about the listeroid drive others were working on.

bob g

[mikenash]

I machined exactly one of those pulleys when a serp drive was necessary or one would get thrown out of the cool club. If I priced making another one even at zero profit I would get laughed at.  Truth of the matter is the actual HP savings over a V belt drive is so neglegable that it cannot been determined except in a laboratory setting. Everything I have set up since that first one uses 2 A section belts, 8.5 OD 2 belt sheave which will have a pitch diameter of around 8.25 depending on manufacturer and engine speeds of 630 RPM or so.
Of course it is up to you how you spend your money but that whole serp belt deal was mostly an unnecessary and expensive fad. If you are dead set on saving a quart of fuel per year via tbe belt drive then go with a V belt pulley and instead of a standard belt purchase a box of A section link belt from Fenner Drives.

I will watch the conversation with interest

Yesterday's task was to resurrect, mount and run an old CS that has sat in a shed for years if not decades - it came to me minus pushrods and a crankhandle but otherwise complete and described as "used to be a good runner"

The process wasn't hard:  Drill 4 X 12.5mm holes in the 20mm/30mm plates and find some M12 bolts.  Mount the motor, strip the fuel system and de-goop.  Find a couple of pushrods and time using the "6 degrees before TDC for intake open and 8 degrees after TDC for zorst closing" system (and I am indebted to the gentleman who published it) . . . and away it went after a bit of cleaning, priming & cranking

Next job is to mount and drive either the Chinese ST-clone head or the Markon - so the discussion on drives is pertinent

https://studio.youtube.com/video/b0RKM9C2ZLU/edit

Cheers

[38ac]

I suppose there are enginering studies that compare belt drive transmission losses but 200 watts less for a serp over an A section V belt?? If have to see that study to believe it. Hope you find what you want but I've not seen many for sale.  Running a diesel any kind of hours is expensive no matter how you do it, good luck with your search.

[KDB]

After all the praise of V belts vs serpentine I started searching which lead to data about different belt types. Two different sites I was on said %5 percent difference. That is 175watts. All of that searching actually lead to another argument that I wasn't really thinking about though. Have you bought a large V belt pulley lately? Or even a small one that would be required also? They are more than the serpentine pulleys I've seen advertised in the past...I'm thinking a notched A profile belt system would be fine but would be more expensive as far as I can tell. Would still want as large as possible pulleys.

[mobile_bob]

after giving the drive system a bit more thought

it might well be the fact that while living in the seattle tacoma area, back when boeing surplus was still open to the public, i loaded up on NOS v-belt pulleys of all sorts.

when you can get martin and browning V pulleys up to as large as 12-14" in diameter and multigroove for pennies on the  dollar, i guess i like most other DIY guys, i bought, and bought, and bought them.  just wish i would have bought more!

i also bought browning belts for a buck a piece!  brand new, some banded multiple groove belts, many matched sets, and a couple of matched sets of the AA hexagonal drive belts i ended up designing my drive to use.

during that time, early 2000's ebay was afloat in alternator drive pulleys that were relatively inexpensive and i loaded up on a bunch of them too.

so i guess it all comes down to what one has on hand and decides to design around.

iirc, and i do remember doing the testing, the AA drive system i designed with the more than 180degree belt wrap, came out to maybe around a bit over 2% loss! that over the direct drive.

it took a lot of testing, measured outputs vs bsfc, a bit of math to derive the the actual losses of the drive system.

5% might be a typical "as designed" loss for the average v belt drive, however that number can be lower with good design.

you know you don't have much loss if you can run for an hour, under max loading, shut down and measure the pulley and belt temperatures and find very little temperature rise.

as far as i know, there are two predominate losses with the belts, one being slippage, the other being flexing/bending.  more wrap dramatically reduces slippage, proper size of belt(s) and diameter of pulleys involved have an affect on flexing/bending of the belts.

i know one thing, that being if i would have measured anything like a 5% drive loss,i would have scrapped that drive and gone to testing a serpentine drive system.

bob g

[38ac]

Bob, What I have seen tested shows an A belt drive to be 95 to 98% efficiant the variation being due primarily to arc correction factor and HP per belt. Theoretical numbers being what they are it would not be complicated,, however quite time consuming to set up a test cell. My curioisity doesn't go that far

[Powdermonkey]

In my experience, I've found two V-belt pulleys supplied with my engines to be entirely out of round.  So....put them on the lathe I did, and squared them up (in a V-fashion).  All that glitters is not gold.  Just be aware that should you endeavor to utilize an Indian V-belt pulley, you might need to dress it up a bit. 

If I recall correctly, I've still got the mandrel for performing such a job, and should anybody need such services, I can handle it. 

[32 coupe]

Years ago, when the "hobby" was at its peak I caught a cast-iron serpentine pulley for my
6-1 set up on ebay. I'm sure it's Indian because it's full of sand casting pits but the bore and
running surface is true and runs a gen head fine at 1800.
I looked everywhere for more of them but haven't seen any. I'm sure I only gave $40 or so for it.


The 25-2 runs a pair of B belts after I gave up on trying to find a serpentine pulley for it at a reasonable
price. Those good quality split pulley set ups are reasonably priced on the bay if you look for open
box or surplus.

[BruceM]

I use a serpentine belt on my 6/1, from flywheel (not grooved) to ST-3 serp pulley,   but found the belt tension has to be quite high to avoid chirping.

So for my neighbors 8/1 conversion (propane, so a 6/1 at 8/1 rpms), ST-3,  I went to a single B belt, which has a fairly good surface area to ride on the flat flywheel, and works well with only moderate belt tension, and saved some cost.  No crown/tracking issues with a vee belt either.

I don't believe in meaningful power savings from the serp belt on a single driven device like a belt driven generator.  With lots of take offs like on a car sure, serp makes sense. 

I think a single B vee belt would do for even an 8/1 diesel.

[Powdermonkey]

I've got a spare serpentine generator pulley.  PM me for details.