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Lowest RPM and V6 engine or any engine can go 2
- Thread starter hafele
- Start date
Well, you said any combustion engine so that doesn't limit us to internal combustion. A steam engine is a form of combustion engine and reciprocating steam engines can make torque at 0 rpm.
I'm sure you meant internal combustion, though, so those 100 RPM slow speed 2-stroke diesels would be the slowest I can think of. They are design rated to run at 100 rpm which means they can overspeed to 110-120 rpm at the most. They don't idle because they are direct drive, but I'm sure they operate at speeds as slow as 50 rpm or maybe slower.
I'm sure you meant internal combustion, though, so those 100 RPM slow speed 2-stroke diesels would be the slowest I can think of. They are design rated to run at 100 rpm which means they can overspeed to 110-120 rpm at the most. They don't idle because they are direct drive, but I'm sure they operate at speeds as slow as 50 rpm or maybe slower.
enginesrus
Mechanical
I suppose if you had a large enough flyweight, you could run that V-6 pretty slow too. But you also would need the valve timing to match.
The Beare sixstroke prototype4 based on a Yamaha TT 500 single produces very usable power at 500 RPM. So much so that it can smoke the rear tire at that RPM with the front wheel against an imoovable object.
Malbeare
Malbeare
My old 1937 Buick inline 8 would idle all day at ~200 rpm and pull easily from that setting without a 'bobble'!
Several of the natural gas/methane V-12 and V-16 Co Gen engines used in the generation of electricity could run in the 100 rpm range but were usually set up to operate at closer to 600 rpm in turbo charged form, at least the units in Orange County and in Santa Barbara County, the ones I worked around.
Rod
Several of the natural gas/methane V-12 and V-16 Co Gen engines used in the generation of electricity could run in the 100 rpm range but were usually set up to operate at closer to 600 rpm in turbo charged form, at least the units in Orange County and in Santa Barbara County, the ones I worked around.
Rod
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GregLocock
Automotive
How fast do you think your engine is turning on the starter motor?
Well OK, I'll tell you: 150 rpm, so it /has/ to be able to run at least that slow, reliably. There are practical installation reasons (driveline resonances etc) why automotive engines are not run more slowly, but in principle there isn't really any particular reason why even quite standard engines could not run very slowly.
One very useful thing would be to be able to run engines up from idle to red line and use ALL of that speed range. This is feasible for a prototype, but would need a lot of changes in various sub-systems.
Cheers
Greg Locock
Well OK, I'll tell you: 150 rpm, so it /has/ to be able to run at least that slow, reliably. There are practical installation reasons (driveline resonances etc) why automotive engines are not run more slowly, but in principle there isn't really any particular reason why even quite standard engines could not run very slowly.
One very useful thing would be to be able to run engines up from idle to red line and use ALL of that speed range. This is feasible for a prototype, but would need a lot of changes in various sub-systems.
Cheers
Greg Locock
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Greg, I disagree. yes a starter might only turn an engine over at 150RPM but the engine doesn't run at 150RPM ussually. The minute one cylinder fires the engine, it accelerates up to at least 500RPMs from the rich condition provided by choke or cold start mode. Yes, some possibly can run at 150RPMs but most cannot. At that low of an RPM the engine has internal friction and loads (waterpump,oil pump, alternator, acpump, ect) that it will loose rotational velocity between power strokes and start to shudder badly if it manages to stay running at all. When it starts to shudder it is very bad for an engine over along period of time. Im not saying all cars cannot idle at 150rpms, Im just saying most cars new and used cannot. I personally think less than 4-500rpms is below its design operation and MAY experience oiling problems below such RPM.
GregLocock
Automotive
I took the trusty Toyota out, warmed it up, stuck it in first, and then braked it down to 300 rpm. Pickup was fine from 300 rpm.
If a 2 hp starter motor can overcome the waterpump, oilpump and alternator friction at 150 rpm then I don't see why a 100 hp engine operating at 1/40th of its rated speed cannot do so.
Really, these things aren't hard to test for yourself, why not do the test before writing notes like that?
Cheers
Greg Locock
If a 2 hp starter motor can overcome the waterpump, oilpump and alternator friction at 150 rpm then I don't see why a 100 hp engine operating at 1/40th of its rated speed cannot do so.
Really, these things aren't hard to test for yourself, why not do the test before writing notes like that?
Cheers
Greg Locock
patprimmer
New member
In my observations things that really help low idle speed are, HEAVY flywheel, small ports, If fuel injected, injecting close to the inlet valve, and sequential, if carburetored, a straight, downward shot from the carby base to the valve and small carby and manifold, short duration cam, minimal free play or backlash in ignition and cam timing devices, NO air leaks, warm manifold.
These observations are from working on pre 1920 cars, which sometimes need to be crank started, and often only have a 2 speed gearbox, and from working on ski boats with dog clutches, and tow cars.
Engine configuration has a minor effect, mainly as it effects port angle for a good downhill shot at the valve, hence tilted or slanted in line is better than upright in line, "V" configuration is better again and horizontal is best.
This applies mainly to carby engines as an injection nozzle aimed straight at the back of the valve will deliver all the fuel to the cylinder every time, no matter where the manifold runs.
The greater the number of cylinders, the less the need for flywheel weight, as 4 or more cylinders always has one on the power stroke, and 6 or more always has one in the effective part of the power stroke.
Longer stroke also helps as it increases piston speed at the specified rpm.
Just my ramblings, for what it's worth
Regards
pat
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These observations are from working on pre 1920 cars, which sometimes need to be crank started, and often only have a 2 speed gearbox, and from working on ski boats with dog clutches, and tow cars.
Engine configuration has a minor effect, mainly as it effects port angle for a good downhill shot at the valve, hence tilted or slanted in line is better than upright in line, "V" configuration is better again and horizontal is best.
This applies mainly to carby engines as an injection nozzle aimed straight at the back of the valve will deliver all the fuel to the cylinder every time, no matter where the manifold runs.
The greater the number of cylinders, the less the need for flywheel weight, as 4 or more cylinders always has one on the power stroke, and 6 or more always has one in the effective part of the power stroke.
Longer stroke also helps as it increases piston speed at the specified rpm.
Just my ramblings, for what it's worth
Regards
pat
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
Many years ago there were engines that were used in small inshore shrimp and fishing boats along the gulf coast that ran on "casing head gasoline" and diesels with very large flywheels that ran less than 100 RPM. One diesel engine a "?Budda?" ran very slow and had no reduction gear only a reverse. Small tugs also ran the same engine only a little larger. On a four cylinder you could count the RPM by the firing
I worked in a shop while in college, working on trenching machinery that was driven by air cooled Wisconsin engines. We had one old rental machine, in particular, that was always around the shop, and when it was around, there was no greater fun than to crank it, (it had a very very slow idle) and as some unsuspecting visitor would walk by, I would grab the spark plug with one hand, and touch the innocent sucker walking by with my other hand.
Point is, the slow idle. If this engine hadn't had such a slow idle, I could not have withstood the energy of the spark ignition in order to pull the trick on others.
Great fun for a college kid, and testimonial to how slow an internal combustion engine can actually idle. (It wasby the way, a v-4 gasoline engine.)
rmw
Point is, the slow idle. If this engine hadn't had such a slow idle, I could not have withstood the energy of the spark ignition in order to pull the trick on others.
Great fun for a college kid, and testimonial to how slow an internal combustion engine can actually idle. (It wasby the way, a v-4 gasoline engine.)
rmw
GregLocock
Automotive
Ha!
we used to have a 4wd forklift on the farm. It had some galumphing great I8 in it.
To start it we decided which cylinder was at TDC, took the plug out, tipped some fuel in, put the plug back in, and switched the ignition on.
Cheers
Greg Locock
we used to have a 4wd forklift on the farm. It had some galumphing great I8 in it.
To start it we decided which cylinder was at TDC, took the plug out, tipped some fuel in, put the plug back in, and switched the ignition on.
Cheers
Greg Locock
Greg, that is similar to the way we used to 'prop' the McCullogh engine in my cousins Benson Gyrocopter. Pull a plug, squirt in a dab of fuel, replace the plug, advance the prop to bdc and flip it in reverse to top. Usually it would fire on the first try. It was a 'pusher' and proping it to start always scared me silly as you had to stand astraddle the fueslage to reach the prop.
rmw---I 'sparked' my friends, unsuspecting passerbys. bugs on the fender, etc. with the same technique using a plug on my old 1949 Mercury. I was only 18 and the 'jolting' wasn't too bad after the FIRST hit. Crazy kids!
Unclesyd---I saw a one cyl (Perkins, I think), similar to the Buddah you mention, on a fishing boat in Texas as a kid. All I remember is it sounded like a "hit and miss" engine. Just kinda 'chug, chugged' along.
Rod
rmw---I 'sparked' my friends, unsuspecting passerbys. bugs on the fender, etc. with the same technique using a plug on my old 1949 Mercury. I was only 18 and the 'jolting' wasn't too bad after the FIRST hit. Crazy kids!
Unclesyd---I saw a one cyl (Perkins, I think), similar to the Buddah you mention, on a fishing boat in Texas as a kid. All I remember is it sounded like a "hit and miss" engine. Just kinda 'chug, chugged' along.
Rod
Does any one remember the old "Johnny Popper" tractor. Huge flywheel.
I remember nosing it into a tree at idle, it would just stand there and --- chug -- pop - pop -- and just spin the rear wheels a partial rev at a time, with each pop. RPM? no guess probably pretty darn slow.
ietech
I remember nosing it into a tree at idle, it would just stand there and --- chug -- pop - pop -- and just spin the rear wheels a partial rev at a time, with each pop. RPM? no guess probably pretty darn slow.
ietech
Sure do, ietech. I have been looking for a bargain "Poppin Johnny" ( Two cyl. John Deere tractor of the 30's) to restore and put in my wife's cactus garden out front. So far I have only found a couple of later models but no 2 banger that is cheap enough. I'll keep lookin'.
Rod
Rod
evelrod,
I got a laugh out of your reply to my post. You are right. That first jolt was the hard one. once you got your mind right, so as to be able to take hold of the plug wire initially, then the rest of it was all fun.
I would be afraid to do it at my age, now, fearing that it would act like some kind of pacemaker and do strange things to my ticker.
rmw
I got a laugh out of your reply to my post. You are right. That first jolt was the hard one. once you got your mind right, so as to be able to take hold of the plug wire initially, then the rest of it was all fun.
I would be afraid to do it at my age, now, fearing that it would act like some kind of pacemaker and do strange things to my ticker.
rmw
evelrod,
After my last post I did a Google search on the subject and found some really interesting sites. Seems I created some new curiosity in myself. Type in "Johnny Popper". Some of the links within the websites listed in the search results have items for sale.
In addition I came accross some great sites regarding vintage/antique industrial engines that others posting here might be interested in reading about. Old LeGrange, Briggs, and others.
All very slow RPM's for those interested type antique engines or vintage engines.
Regards,
ietech
After my last post I did a Google search on the subject and found some really interesting sites. Seems I created some new curiosity in myself. Type in "Johnny Popper". Some of the links within the websites listed in the search results have items for sale.
In addition I came accross some great sites regarding vintage/antique industrial engines that others posting here might be interested in reading about. Old LeGrange, Briggs, and others.
All very slow RPM's for those interested type antique engines or vintage engines.
Regards,
ietech
patprimmer
New member
Also, longer stroke means higher piston speed and probably higher gas velocity in the ports and manifolds at a given rpm, as longer stroke, smaller bore often means smaller valves and ports
Regards
pat pprimmer@acay.com.au
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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
When was a kid the Panther motorcycle was a reasonably common machine in UK; they were often used to pull a sidecar. The bikes had a very long stroke forward inclined single cylinder 600cc engine. In top they were so slow-revving that a common description was "one bang every lampost" ;-) .
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