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Steel Soldiers now has a few new forums, read more about it at: New Munitions Forums!
Why 2650rpm max?
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WOW, now that is big
saddamsnightmare
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November 25th, 2010.
Happy Turkey Day, Gents!
I have sat back and admired the intellectual powers brought to bear on the question of rod bolt failures, and the acuity brought to bear on solving the issue at hand. Might I ask, why do you suppose Uncle didn't go down this street before we did? The truck was designed to be a slow speed off road truck back in 1948, limited by contract costs and technological limitations present at the time. The Unimog shares many of the same issues, but with the M180 gas engine coming from a car, it can take sppeds a heavier diesel can't reach.
However, neither truck was really intended to run much above 25-35 MPH at best, and off road use and design almost guaranteed these trucks would be run at about 10 to 20 MPH speeds most of their lives..... So the question really is one of, if we ran the trucks at 20 MPH off road all the time, how many rods would fail in the course of a year? My M35A2 has spent most of its 32K miles since Desert Storm and the last rebuild at 22.5 MPH average. THE problems have come from trying to run her at 50 MPH for hours on end on the road (that and a rear main failure).... The lesson is to obey the laws your truck was designed to operate under, do the PMIS, drive it like we have brains under our hats, and the trucks will probably last as long as the many Model "T"'s have (and, oh, yes, they have speed related failures too, when driven over 35 MPH for very long....)!
I am still on the fence as to whether to give "Saddam's Nightmare" a new owner down in Texas, or truck her up here to my new home. At least the new home commute would be 1.8 miles each way at about 30 MPH or less, so it looks like an M35A2 and a Unimog S404.114 stands a good chance of surviving in that operating environment.... BUT if anyone's interested in a deuce, look me up.
Happy Turkey Day, Gents!
I have sat back and admired the intellectual powers brought to bear on the question of rod bolt failures, and the acuity brought to bear on solving the issue at hand. Might I ask, why do you suppose Uncle didn't go down this street before we did? The truck was designed to be a slow speed off road truck back in 1948, limited by contract costs and technological limitations present at the time. The Unimog shares many of the same issues, but with the M180 gas engine coming from a car, it can take sppeds a heavier diesel can't reach.
However, neither truck was really intended to run much above 25-35 MPH at best, and off road use and design almost guaranteed these trucks would be run at about 10 to 20 MPH speeds most of their lives..... So the question really is one of, if we ran the trucks at 20 MPH off road all the time, how many rods would fail in the course of a year? My M35A2 has spent most of its 32K miles since Desert Storm and the last rebuild at 22.5 MPH average. THE problems have come from trying to run her at 50 MPH for hours on end on the road (that and a rear main failure).... The lesson is to obey the laws your truck was designed to operate under, do the PMIS, drive it like we have brains under our hats, and the trucks will probably last as long as the many Model "T"'s have (and, oh, yes, they have speed related failures too, when driven over 35 MPH for very long....)!
I am still on the fence as to whether to give "Saddam's Nightmare" a new owner down in Texas, or truck her up here to my new home. At least the new home commute would be 1.8 miles each way at about 30 MPH or less, so it looks like an M35A2 and a Unimog S404.114 stands a good chance of surviving in that operating environment.... BUT if anyone's interested in a deuce, look me up.
Green Toys
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All the different ideas on here and no one has thought about the down pressure on a turbo charged engine. While reving under a load my LDS 465 1a has 10-25 psi of boost, soo the turbos
drive pressure is at least 20 PSI. with this pushing down on the piston all the time either boost or drive pressure the rod is not putting much force on the cap of the rod. Right???
drive pressure is at least 20 PSI. with this pushing down on the piston all the time either boost or drive pressure the rod is not putting much force on the cap of the rod. Right???
It isn't the indicated speedometer speed that throws the rods, it is the indicated tachometer speed. These trucks threw rods when they were doing line haul probably more frequently than they do now in our service. Check out the letter that David Doyle found where the DOD was complaining about just that problem. When you are in a low gear, it is hard not to have the engine up on the governor's limit.
If you want to see the rod failures drop down into the noise, set your governor to max out at 2200 to 2300 rpm.
-Chuck
If you want to see the rod failures drop down into the noise, set your governor to max out at 2200 to 2300 rpm.
-Chuck
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Boost will add stress to the rod but only compression stress, this is where the rod is very strong. It would not have much effect on the bolts or cap. If you look at SS tractor pullers they run up to 250psi manifold pressure. Failures are common. While often it is hard to tell what broke this video is of one breaking the block in half. I have also seen a crankshaft/rods/pistons driven out the bottom of the block, ending up on the ground. Makes you wonder what happen to the clutch/trans. I guess that would have to break both ends of the crank, all the main cap bolts, pan...Maybe I can find that picture.
YouTube - Tractorpulling insane engine blow up, Engine flys out of the tractor!
25psi is an awful lot of boost for a non intercooled engine. I started getting high EGT at 15psi-16psi (M35A2) so use 12-14psi currently. Any boost related rod compression stress would rise and fall as the boost does. It would be minimal at cruise.
My point being - RPM is hard on rods/bolts. Power (as in combustion) is not.
Here is another(last pic-Cummings bock failure).
YouTube - Too Many Horses - Cummins Engine Blows up!
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YouTube - Tractorpulling insane engine blow up, Engine flys out of the tractor!
25psi is an awful lot of boost for a non intercooled engine. I started getting high EGT at 15psi-16psi (M35A2) so use 12-14psi currently. Any boost related rod compression stress would rise and fall as the boost does. It would be minimal at cruise.
My point being - RPM is hard on rods/bolts. Power (as in combustion) is not.
Here is another(last pic-Cummings bock failure).
YouTube - Too Many Horses - Cummins Engine Blows up!
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Green Toys
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Pulling a load I maintain 25 psi of boost. My truck has a Intercooler installed and it makes a huge difference. I never let the egts go over 1200.
jwaller
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mine is almost the same as his, 20psi on the gov limiter and water injection. never over 1200degrees.
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Is this a M35A2 you're talking about? If so,
I'm just curious how you shoehorned a intercooler in there.
Gamagoat1
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This is some great reading. The one thing I see that is not considered enough is balance.
These engines (Military) are assembled from premanufactured parts. They (the parts) are manufactured to a specific standard, and it is assumed that they will be OK when put to work. Once the engine is assembled, there is no effort to check balance or further balance the rotating mass. Can this be a large part of RPM limitation and subsiquant failure?
Try balancing a little 230 c.i. Dodge for a M37 if you want to see huge improvements in operation and durability.
These engines (Military) are assembled from premanufactured parts. They (the parts) are manufactured to a specific standard, and it is assumed that they will be OK when put to work. Once the engine is assembled, there is no effort to check balance or further balance the rotating mass. Can this be a large part of RPM limitation and subsiquant failure?
Try balancing a little 230 c.i. Dodge for a M37 if you want to see huge improvements in operation and durability.
Green Toys
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Is this a M35A2 you're talking about? If so,
I'm just curious how you shoehorned a intercooler in there.
Check this out, http://www.steelsoldiers.com/5-ton-up/43109-m52a2-aia-air-intercooler.html
I wish I could take credit, b/c he did a great job on it, with all the other mods I have done I get a 300 degreze differintal between the air going into and coming out. Very Impressive. By the way I cant Spell. LOL
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Yes, I've seen that thread. I've still never seen one added on a M35A2.
jesusgatos
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I'm not trying to turn Mah Deuce into a dragster, but I've got a fresh LDS sitting in a crate and was planning on re-torquing the rod-ends and mains anyway before I install it. Not knowing the history of a rebuilt engine like this (or any of the engines in our trucks), my question is - why NOT replace the rod-bolts if you're in there anyway and parts are available and reasonably priced?
I'm in the 'better is better' camp and I'm inclined to improve on just about anything/everything that I'm able to. In this case, I'm planning on putting a lot of miles on Mah Deuce, living in it and doing some extensive traveling, so I'm inclined to go overboard anywhere I see an opportunity to improve on anything - either to increase performance/comfort/drivability, or to prevent a potential failure. It's only time and money, right?
Let me know if you need any help with this. I don't want to cut-in, but I've worked with ARP in the past and have contacts there that might be able to tell us what we want to know. If they have any parts on the shelf that will work for us, seems like a no-brainer to me. Cheap insurance. If they'd have to make custom bolts, then I'd want to know more about whether this is really a problem that needs to be solved before going any further.
http://www.steelsoldiers.com/deuce-modification-hot-rodding/6731-pulling-tractor-deuce-engine.html
I was searching and ran across this older thread. 4000 rpm at the starting line and 500hp...
Does anyone know what the injection timing is? I thought I read somewhere that it was 20 deg BTC. Could this be putting a huge load on the rods and everything?
Too much advanced timing in a gas engine can lead to pitted pistons, sheared cranks...
The 7.3 ID Turbo in my 94 F350 has factory timeing of (6 ?) deg After TDC. Performance guys at desiel truck.com say to go 6-8 deg before. That's a long way from 20.
Does anyone know what the max timing is for the Cummins, Power Stroke... and with a chip?
The guy above used stock bottom end, but had things balanced. So if he could run full throttle 3500 rpm at a tractor pull with stock rods that lasted atleast a couple years, What was terribly different?
Lighter modified pistons, balanced, and...
Just food for thought.
Does anyone have close up pics of failed rods? That may help.
I was searching and ran across this older thread. 4000 rpm at the starting line and 500hp...
Does anyone know what the injection timing is? I thought I read somewhere that it was 20 deg BTC. Could this be putting a huge load on the rods and everything?
Too much advanced timing in a gas engine can lead to pitted pistons, sheared cranks...
The 7.3 ID Turbo in my 94 F350 has factory timeing of (6 ?) deg After TDC. Performance guys at desiel truck.com say to go 6-8 deg before. That's a long way from 20.
Does anyone know what the max timing is for the Cummins, Power Stroke... and with a chip?
The guy above used stock bottom end, but had things balanced. So if he could run full throttle 3500 rpm at a tractor pull with stock rods that lasted atleast a couple years, What was terribly different?
Lighter modified pistons, balanced, and...
Just food for thought.
Does anyone have close up pics of failed rods? That may help.
Strykerboy
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I've reved up a ldt-465 past 3,000 rpm and they do it... just not for long, that turbo get's REALLY HOT! then a nice sized flame of burning oil and smoke shoot's out of the stack and engine shut down happen's....
note: i was pulling a huge 50+ foot old oak tree out of the wood's 
note: i was pulling a huge 50+ foot old oak tree out of the wood's 
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Consider this if your going to compare tractor puller's engines. They run for about 5-10 seconds at full throttle/full load. 10-15 pulls a year. That's full power for 2.5 minutes/year. And they do blow eventually.
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Nope!
The MF engine is NOT a spark ignition gasoline engine... Nor is it a conventional diesel engine.
The special juju of the MF engine is a deep well combustion chamber bored into the top of the piston ( It looks like what you would get if the piston was made of modeling clay, and you stuck your thumb deep into the center of the piston top), the injectors, the early timing, and the very high compression ratio.
The injector does not atomize the fuel like a conventional diesel engine does. Instead, it squirts a stream of liquid fuel (much like a squirt gun) into the combustion chamber in the top of the piston. The fuel splashes, and boils. When the fumes bubble up into the hot air in the combustion chamber, they burn... relatively slowly. That is why you need the greatly advanced timing on the injection pump. That is also why MAN, the inventors of the concept that became the MF engine, called it a "Whisper Diesel".
A conventional diesel engine has high pressure injectors with small openings that atomize the fuel. Because the entire charge of diesel particles is instantly spread throughout the high temperature air, it explodes almost instantly. That accounts for the heavy knocking sound you hear in conventional diesel engines. It also accounts for the near TDC timing used in conventional diesel engines.
The MF is NOT a conventional diesel engine.
-Chuck
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mckeeranger
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Go to the first post in this thread: http://www.steelsoldiers.com/deuce/44121-55mph-detonation-11.html
There is more than one thread with ventilated engines, but this one has a couple of good pictures of the momentarily ballistic parts. The rod, anyway.
JDToumanian
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They don't actually.... My Detroit 6-71N red lines at 2100, but because every downward stroke of the piston is a power stroke (as opposed to every other stroke on a 4-cycle engine) my Detroit SOUNDS like it's doing 4200!