it makes me happy that so many of you guys remember Quinn
there is hardly a day goes by that i don't think of him.

he belonged to an email group that includes me,  so i got to correspond with him
several times a week for the last 8 or 10 years.

i talked to him on the phone about a month before he went to the big shop in the sky, and wish i had taken more time to give him a call.

as a christian i am told that God has a plan, but darn it just doesn't  seem fair that he was taken so soon.

oh well, i bet he is building a new shop for all of us to enjoy when the time comes.

thanks for the memories guys

bob g

IMQ

merry Christmas to all, and my hope is we all stay healthy
all the best from my family to yours

bob g

+1 with John at gaskets to go!

his gaskets are absolutely state of the art

i had him provide me with head gaskets for my s-195 and he sent me a half dozen for about 7 bucks each, that was maybe 12 years ago?

they are of vastly superior construction, carbon/metallic with print o' seal around all the water ports, excellent gaskets

i say this based on the extreme use i put them through, running the engine at max load with a pressurized cooling system running between 205 and 214 degF, absolutely no leaks or weeping at all.

far superior to the oem gaskets, and i suspect a quantum leap over indian head gaskets.
at 7 bucks each i can't imagine even thinking of trying to make one unless it was a zombie apocalypse and i had nothing to replace one with.... even then it would be a tall order to get something that would work for any length of time.

bob g

i suppose there are always exceptions, but the japanese diesel engines used in datsun, toyota, isuzu and others have proven to be nearly indestructible.

i recall working for a time for a roof truss company north of seattle, they gave me an old '81 datsun 3/4 ton with a 4 cyl diesel, they told me maybe i should service it as no one remembered the last time it had an oil change

the oil came out black as sin, but that is no big deal in a diesel, however the thing had 186k miles on the clock and was running the original primary fuel filter, still had the factory marks on it.  the air filter i could not get out of the housing, as it was a solid dirt clod

i removed the complete assy, beat it to death with a rubber mallet to get the clod broke up and get the filter out, it to might have been original, i never looked that close.  took a steam cleaner to all the piping and housing to clean it out, and put it all back together.

i overheated the thing one morning, the dash lights didn't work, and i had no idea it was hot, broke an oil cooler water hose, and blew the head gasket,... pulled the head, cleaned it all up, put in new gasket and away we go again.

lost the front brg in the trans at 220k,  center rivets failed in the clutch soon thereafter, i don't recall why we didn't change the clutch when we replaced the trans.

at 331k miles the little truck was sold for 300 dollars, and for all i know the little bugger is still running somewhere.

it was the only 4 wheel vehicle i could run along side a push start  on cold mornings.

a courier company i did business with had 60+ G series 3/4 ton chevy van's with 350 cu/in small blocks, they were impeccably maintained and they routinely got 350-400k miles out of them before they were sold.  they had all the normal stuff replaced on a scheduled basis, no running to failure, they knew exactly when to change every part of the van, such as 91k miles for an alternator, 75k miles for a starter, waterpumps, timing chains etc,  they hardly ever had a breakdown. and i bought a couple of their old vans for friends to pull the engines out of for other projects. 

fwiw, they used series 3, 15/40 motor oil (same as used in the cummins powered fl-70 freightliners) and they changed the oil in those vans every 10k miles!

i never understood how that work, other than the engines started at 5am and didn't shut off again until they came in at around 4:30 in the afternoon.  so i have no idea how many hours were on the oil changes at 10k miles but it had to be a bunch.

i think engines can last a very long time with excellent maintenance, and not started, stopped for short runs a dozen times a day.  locomotive engines are an example of long lived engine's, i don't think they are ever shut down.

bob g
 

luckily we don't need an engineering degree to determine critical speeds
we can simply call the engineering dept of the manufacture in most cases, and in those that we can't (such as the changfa) it is so easy to determine if one is motivated to do so.

99% of folks with a changfa in this country, will run the engine at or near its rated rpm if belt drive, or at 1800rpm for 60hz direct drive, either speed is above at least one critical speed.

my trigen is built with resilient 3 point mounting, with the mounting axis inline with the crankshaft and st head centerline (being direct drive).  with the 3pt mount and resilient mounts, i can slow the engine and find a critical speed iirc at or around 1200-1300rpm
where there is not only much more noise from the countershaft gear clatter, but also a pronounced rocking motion and a heavier overall vibration. 

because it not only drives the st head but also twin 555 alternators, i don't want to run at that rpm, and found that by reducing to 1000rpm everything settles down again and that is where the low speed control was set.  the critical speed range not only was noisy and a lot of vibration, but because of the rocking moment of the assy and the outboard mounting of the twin alternators, i didn't want them shaking back and forth violently.

so at high speed it runs at 1800 for direct drive 60hz, at low speed 1000rpm for the twin alternators and lower db and fuel consumption.

in my opinion the changfa's are very tough compact engines, the crankshaft is very short and stiff with the flywheel mounted close to the outer main brg. it is doubtful that one could damage one of these engines running at any rpm below that which would start throwing parts all over the place... i have no idea what rpm it would take, nor do i want to know.

all we have to do is look to the guys that put them in trucks and haul all sorts of stuff, lugging along, stalling, lugging, and then reving like hell going down the hill.  tough little engines.

so i don't worry about the engines critical speed doing damage to itself, but i do know that it is hard on driven components.

now give me a 13hp chinese clone gas engine?  and yes i would be more concerned with critical speeds for the engine longevity. i would probably check with honda for one of their gx390's to see what they publish about operating ranges, and if i could i would talk to an engineer at honda about any critical speed concerns, that is "if" i found that once i built something the thing seemed to vibrate heavily at my chosen rpm.

i don't like things that vibrate, especially with thin aluminum crankcases containing the problem.

but that is me, and  i am a bit more particular i suppose.
and it would also depend on my intended use, if it were some intermittently used unit
maybe quick and dirty has its place, i can agree to that, but

if it is something that i anticipate running long hours, having to depend on its continued operation, then yes i will be doing everything i can to see that it is done right, and i will not be running at any speed that produces unusual vibration.

fwiw, which is worth about half what you paid for it.

bob g

hwew

you should be deeply flattered my friend, it is generally only movie star hero's that have man crushes!

i can feel the warm glow all the way here!

bob g

you know its ok to be flattered, we are an all inclusive, non discriminatory group of folks here, we won't think anything less of you.

another example of critical speeds i witnessed first hand back in the late 80's while working in a truck shop, they had a "on truck" wheel balancer, that would allow for balancing the complete rotating assemble, hub, drum, wheel and tire.

now i understand that this is a balance issue, but it was very interesting that the critical speed was not a single speed but sometimes as many as 3-4.

lifting the front axle off the ground, just off center, so that one tire was still in contact, but most all the weight off of it, we would spin up the lifted tire with a 10hp 3phase 3450 rpm motor with a friction drive. 

it was interesting to see the doors while closed on the truck, literally hammer themselves in the door jambs to the point that it would chip paint! 

as the wheel began to slow down, the doors would stop pounding, and slow a bit more they would start back pounding again, then quit when it slowed a bit more, etc etc

these were examples of critical speeds that could be correctly rather easily with lead weights,

it was pretty easy to tell, that uncorrected one would not want to drive the truck at any of those speeds, because while the doors probably wouldn't start beating around, it is likely one would feel the vibration even though dampened and decoupled by tire to road contact.

btw, that blackstone is a monster!  and i love it!

bob g

(i typed the following late last evening, but forgot to hit "post" so it is probably out of sequence)


i have been guilty in the past of getting into the weeds, and over time found it to be non productive for myself and for the members of the forum.

we can argue fine points, and believe me i can do that as well as anyone
but what is to be gained?

when i mention the oem recommendations on operating speed, i should have expanded on that a bit perhaps, and related it as  recommended "operating range", rather than speed.

i think most folks understand that.

most all stationary engine manufactures, or those that build for that purpose, and for purposes of heavy loading in particular do recommend an operating range.  by that it is meant  that this is the range of speeds that the oem recommends the use of their engine under load.  stationary engines are likely far more heavily loaded than the typical automotive engine which can get by quite nicely operating over anywhere from idle to redline (which btw is a recommended don't go over line)

lets take hwew' kubota single cylinder diesel, iirc it is rated for 2600-2800rpm at rated load, and the power curve stops at something just over 2200rpm or so, its not that the engine won't run under 2200, its just that it vibrates badly at around that speed.  likely one of the critical speeds that they don't recommend running at, especially under load.

(my  bet is hwew has talked to the kubota engineers about this issue.)

it is apparent to the user that this is not a good speed to operate at, because the thing shakes and vibrates so bad that it works parts loose, which generally is not a good thing, unless you want a asphalt packer or concrete screed vibrator ?

getting back to automobiles and critical speeds, these engines are generally very stiff, compact, well balanced, well engineered, with serious attention to things like harmonic balancers, and engineered mounting systems, along with the decoupling effect of the almost ubiquitous automatic transmission.

go back to the 40's and early 50's and the 6cyl stick shift transmission cars and trucks, one could certainly determine by feel what he might not understand as a critical speed but knows that "hey, i don't want to drive in this gear, this thing vibrates my teeth out"
its doubtful that the oem's had to make a recommendation on what engine speed to operate under, they left it to the user who figured it out within the first few blocks of leaving the dealership, or....

he was like some of those old farts that lugged the crap out of their car or truck and you could hear every part of the vehicle vibrating like mad, gears clatter, driveline ringing a horrible tune, and the old deaf guy oblivious to what was happening, or he was driving down the road in first gear at 55mph turning 6 grand! (that was my poor dad, he couldn't hear a thing)

as for your point on industrial engines and power curves, and folks not aware of such, i think you are sadly misinformed.  while there might be some newbie that doesn't know about such things, it is doubtful that you will find but a tiny percentage of the members on this and other forums that are unaware.

(skipping down a bit to your cummins reference)

if we go back to the 60's and early 70's cummins made a taper nose ntc335 engine
it had a critical speed problem in that if you loaded the engine at a certain speed you ended up with a broken crankshaft

ford tractors, 50's with the 4cyl diesel had a similar problem, recommendation was to not load the tractor at some specific rpm, i don't recall what it was either, but broken cranks were not uncommon.

the reason that cummins is now able to get max torque down to 1000rpm is they have built the engine massively stronger than it has ever been.  you can build any engine heavy enough to stand up to about any critical speed issue you like, but almost without exception, the bean counters don't want an oz. of extra iron or expense put into a design without very good reason.

car and pickup reference again

the engine in the typical 5k lb suv has what? 300hp or more these days?
what does it take to in hp to move a 5k lb suv at highway speeds, maybe 100hp?
what does it take to plug around town at 30mph? maybe 25 or 30 if the a/c is on?
the typical car engine is asked to deliver on average probably a quarter of its capacity
and likely half of that driving around town, with brief excursions.  so maybe you are lugging around at some critical speed in your car, putting around town, however because the engine is built to make upward of 300hp it is over built for the need required to putt around at that speed, it is decoupled and isolated so the driver has no feel that it is even happening, and yes it is not a problem.  don't feel it therefore it doesn't exist?  ya right.

every engineering book ever written on internal combustion engines, beit for cars, trucks, planes,  trains, boats, or anything else has a chapter on critical speeds and what is done to deal with them..  you either overbuild and isolate the engine, or if you can't you instruct the operator on where not to run the engine under load.

i mentioned the ferry boat
they are an interesting case study in critical speed

the engines are generally very rigidly mounted to the boat superstructure, and as such engine vibration is transmitted through the hull and around the boat.

when the captain leaves the dock and starts to throttle up he does so , increasing rpm slowly, sometimes remaining at a lower rpm while he clears the dock and/or other obstructions, but as he increases the rpm the engine will enter critical speed, at that precise moment you can feel the boat start to violently vibrate and you can also feel the surge as the captain shoves the throttle open so he can quickly pass through that rpm.

it is actually very interesting to witness having studied the phenomenon, to actually feel the process from before, during and after.  its not something most of us would think about, but that captain sure does.

after witnessing that i went looking for other examples, and came across a railroad yard, and found the same thing taking place, they start to slowly throttle up, then at some rpm the ground starts to vibrate and the engineer cracks up the throttle and he gets through that rpm quickly.  again very interesting.

if you would like i can refer you to a two volume set of engineering books from MIT on engine design, believe me critical speed is a very real thing that must be dealt with one way or another.


its been a very long day, i will part with you for now
and time willing,  pick up where we left off tomorrow.

fair enough?

bob g