More on the subject from one of my mailing lists posts:
From: cherev
To: morgan
Sent: Thursday, November 01, 2007 4:25 PM
Subject: [morgan] Perkins 4-154 fan belt info, again
What would it cost, both in money and time, to simply replace
the sheaves with a matched set that uses a broader belt? A common
type, such as the kinds used on diesel trucks?
In the process, the alternator and pump shafts could be slotted
and keyed so that these would be easier to maintain, i.e., no
need for a 1.5-tonne press to press on a sheave, nor a special
tool to extract one.
Seems to be a mite of angst being spent on a simple mechanical
problem, unless the alternator(s) are also wonky.
I don't think it possible that I have 5 wonky alternators...
New pulleys is one of the remedies I've considered. The trick is
in getting all the offsets right, in addition to all the
different mounts.
The alternators have a shaft which is hex keyed to keep it from
turning - but I haven't the strength (and I routinely break stuff
because I'm too strong on a bolt, tool, etc.) to get my 3/8
pulley off the other alternator to swap it on to the one
remaining functional (of 5) alternator.
The driveshaft is splined and keyed - held on by a massive bolt -
and has some dishing and other shape potential issues, plus it
has to have the right face for the PTO end which drives the raw
water pump with its sheave (1/2" - go figure, it's bigger than
the alternator belt, and doesn't have nearly the required force),
which PTO bolts to it.
The freshwater pump is essentially a bowl of stamped steel, with
a ring pressed on to it, and a resultant offset of 3-4 (I've not
measured it) inches.
All these would have to be duplicated. If you've got a
comprehensive source for such pulleys, I'm all ears. Otherwise
the next best thing might be to have the main shaft pulley, solid
steel, machined to the same size/angles as the alternator's 1/2"
belt, and buy the appropriate cogged belt in 1/2 (giving me
whatever the resultant greater surface area [and strength]
resulted)...
For now, the 10mm belt is what was specified, and is much less
hot after running, so between the fact that it actually fits in
the drive pulley, and isn't as hot (better tight turns? more
surface area? I don't know why), I'm going to expect a better
life from it.
So, I'm going to see how this one lasts. If it's not an
improvement, then I'll bite the bullet and get the pulley off and
turned, and go to 1/2" belts. The freshwater pump shouldn't
matter, I don't think; it's just a stamped dish with a ring
pressed on; clearly it's not intended to carry any load, so I
expect the 1/2" would drive it just fine, and not negatively be
impacted by its smaller size.
I can say for sure that after some heavy charging last night, I
felt the belt after over an hour of running. It was hot, but
nothing like the prior belts I'd been using. I've also heard
from several, now, who say that the solid belts I'd been using
were disintegrating on them, too, and changing to the cogged -
whether topcog (Dayco) or internal) seemed to dissapate the heat
better, as well as, perhaps, give better close-radius
performance.
However, I have all of perhaps 5 hours on this belt. I've
tightened it once, and both that and the first were extremely
tight - a recommendation from an alternator vendor (Hotwire) and
others - to cope with the higher output. Given how many belts
I've been through, though, some experimentation is in order; I'll
not tighten again until I hear squeal or smell smoke. I check it
literally every time I stop the engine and again before I start
(other than panic modes, of course), so I'll have a good feel for
what the tension was before squeal and smoke occurs.
I'm triangulating on the failure modes as well as the solutions.
I know about the wallet mode; I could probably get a backyard
hobby guy to turn me a brand new set of pulleys cheaper than
buying something used, and get a 1/2" set in the bargain :{))
One of the guys I was working with in St. Pete (Erkki, from my
logs if you recall the first leg of this trip) was such a guy.
He'd enjoy doing it - but I don't have one of those to hand, nor
do I have the time, now, to do it. However, I might do some
downtime this winter, to address my atrocious electrical system;
if I did that in St. Pete, I'm sure he'd not only help with that
but enthusiastically participate in the other stuff. Best news
is he's a retired rocket scientist (used to design satellites for
Canada) and does it free for lunches - cuz he likes it...
And, finally, I got the proper Perkins "old" part number. It's
NA003439, and 25/64 x 49 5/8, or 9.5-10mm X whatever that works
out to. That would be long enough that I'd not get more than one
tightening on it, so I'm using one quite shorter.
L8R
Skip
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