Runaway multifuel 6/20/14

[o1951]

Interesting questions. Regarding CO2 delivery, at 3600 rpm air flow in would be about 8.33 cubic feet per second, so this would appear to be the maximum rate that CO2 would have do discharge from a container. A 5-lb cylinder contains about 44 cuft of CO2; venting at 8.33 cfs would empty the cylinder in about 5 seconds at 32 degrees F and 1 atmosphere. The cold venting CO2 would quickly start to drop the engine temperature and would also be expanding rapidly as it [CO2] heats up, so a slower delivery rate is feasible. Anyone have any idea how quickly a cylinder can vent? The net result would seem to be that a longer emptying time might be acceptable. Rustystud pointed to rapid slowing, so 10-?? seconds of CO2 delivery might be sufficient. It would interesting if someone out there with such a system in place had some idea of the numbers and posted a stop time, if such a person is willing to run a potentially pricey experiment!

Actually, would not need that much co2. Air is about 21% o2. All system has to do is get the o2 level at or below LEL, and no combustion. Do not have to blanket it and exclude almost all air.

 

[o1951]

There is all this talk about CO2, would putting it in 5th and stalling it not work?

Would seem so, and I have done just that a couple times in my life on civy gas engines that ran away when turning key off would not stop it. I found it very difficult to get trans in upper gear at high rpm's even with clutch full in.

As stated on this forum, and as some people in civy diesels that ran away told me, they could not get trans into gear even with clutch depressed. Could it be that at over speed, trans input shaft keeps turning with clutch in, preventing engagement? I don't know, hope never to find out.

 

[rustystud]

During a run-away as the original poster had happen, engine speed would be very high. The issue of fueling from lube oil would require choking or extinguishing with carbon dioxide.

If your leaking that much engine oil into the combustion chamber to fire it off, you have more problems then just a injection pump installed wrong which was the original problem. Contrary to popular belief, it takes quite a bit of oil to fire off a diesel. Usually the turbo is leaking.

 

[Torisco]

I just do not want to take ANY chances with a runaway so I found a used Rado Deaco air intake shut off valve from a Peterbuilt and modified it to be a manual T-Handle cable pull in the cab that slams the air gate shut immediately. Tested this at close to 2500 RPM and it shut the engine down immediately. I figure I will probably end up changing a head at sometime, or mess with the injection so for peace of mind I installed this item. I am currently trying to see if I can hook up the automatic shut off feature of Rado Deaco based on a preset maximum RPM setting.

The military NOS T-Handle control cable has "Emergency Engine Stop" embossed in red on it. These were used in the 5 ton military trucks .

Having experienced this runaway up close and personal, it's not something I want to do again. A quick shutoff like the butterfly valve would be well worth it just for piece of mind, even if it never occurs again. There would be no way I could have got that mushroom off quick enough to do any good had I not done so as a precaution.

 

[todds112]

Nice job!

 

[rustystud]

I just do not want to take ANY chances with a runaway so I found a used Rado Deaco air intake shut off valve from a Peterbuilt and modified it to be a manual T-Handle cable pull in the cab that slams the air gate shut immediately. Tested this at close to 2500 RPM and it shut the engine down immediately. I figure I will probably end up changing a head at sometime, or mess with the injection so for peace of mind I installed this item. I am currently trying to see if I can hook up the automatic shut off feature of Rado Deaco based on a preset maximum RPM setting.

The military NOS T-Handle control cable has "Emergency Engine Stop" embossed in red on it. These were used in the 5 ton military trucks .

Nice clean install ! How much did it cost ? Did you get it at a junkyard ? or some online auction site ? Thanks.

 

[Torisco]

I got the shut off valve equipped with a pneumatic/electric cut off set up (which I still have the accessory parts for). I converted it to manual pull cable control from the cab. It was purchased at a auction for around $155.00 plus S/H.

The three ply silicone turbo hoses were around $40.00 each. (three cost me $150.00 with S/H) These could have been gotten for less if I was not in such a hurry and looked around more.
The three hoses were a 4" dia to 3.5" dia adapter hose, a 3" dia to 4" dia adapter hose, and a 3" dia to 3" dia hump hose. I also needed a pull type control cable for around $30.00, six 3-4 " hose clamps and a fabricated extension bar from the valve actuator to connect to the end of the control cable.

Total parts cost around $350.00 total. (A NEW Rado Deasco shut off valve equipped like the one I got at auction runs around $800.00 while most used ones average around $200-350.00).

Nice clean install ! How much did it cost ? Did you get it at a junkyard ? or some online auction site ? Thanks.

 

[jhooah]

480 cubic inches, 240 per revolution as it is a 4 stroke. 3600 rpm so 86400 cubic inches per minute, that is 500 cubic feet. One pound of carbon dioxide is about 8 cubic feet so a one pounder needs to be discharged at 8/500 minute, roughly one second.

sounds like a five pounder is necessary.

In my limited knowledge I would tend to disagree, you don't need 100% CO2 to kill it, just enough to make the air fuel ratio degraded to the point combustion cannot occur, or fails to overcome compressive forces created through inertia of the engines turning mass. If the fuel does not detonate, the cycle cannot continue. For gasoline I think it was 12:1 or such, I'm no rocket scientist to elaborate on the air to fuel mix required for Diesel (or oil) to keep the combustion cylcle running.
V/R W Winget
OOPS, just saw o1951's post above after I had posted, but I fully agree, just eliminate "enough" air and it dies. WAW

 

[Keith_J]

Some diesel engines can operate with 50+% exhaust gas recirculation, note there is a lag time as when first EGR kicks in, there is more oxygen in the exhaust gas. Progressively, the oxygen content decreases but since there is always fresh air (measured by mass) intake, the engine won't die.

It would take a bit more than 50% carbon dioxide to snuff out a diesel. Remember, it is partial pressure, not concentration. With a 17:1 compression ratio, you have plenty oxygen even at a 5% concentration at atmospheric pressure once it gets to pressure.

This is why intake throttles work well, they reduce manifold pressure in essence dropping the mechanical compression ratio down to less than 1:1.

 

[Wolfgang the Gray]

There are two things with these trucks that scare the crap out of me and always make me mildly paranoid: 1. A runaway engine 2. The brakes failing. I hope the engine isn't damaged... Keep us in the loop.

If you lose the brakes, can't you just down shift and shut the motor off, letting the engine compression do the braking?

I've only been registered on Steel Soldiers 2-days, but this site & everyone here is providing so much valuable information to me as I am getting close to buying my first M35A2. Thanks to everyone here, you all ROCK!!!!

 

[welldigger]

If you lose the brakes, can't you just down shift and shut the motor off, letting the engine compression do the braking?

I've only been registered on Steel Soldiers 2-days, but this site & everyone here is providing so much valuable information to me as I am getting close to buying my first M35A2. Thanks to everyone here, you all ROCK!!!!

There is no throttle plate like in a gas engine. A diesel engine will slow down a tad by downshifting but generally the momentum of the truck will push right through the compression stroke. Since there is no throttle plate there isn't anything to put a hard vacuum on the engine to slow it down. So no, downshifting is not really a viable option.

 

[gimpyrobb]

The parking brake won't help either!

 

[welldigger]

The parking brake won't help either!

Well....I mean you will get about a second of braking before it turns to slag....

 

[Wolfgang the Gray]

There is no throttle plate like in a gas engine. A diesel engine will slow down a tad by downshifting but generally the momentum of the truck will push right through the compression stroke. Since there is no throttle plate there isn't anything to put a hard vacuum on the engine to slow it down. So no, downshifting is not really a viable option.

Thanks for the info. Guess I could always carry a 500 pound anchor in the back & have it drop out the back with a long chain & just start grabbing at stuff to stop with.

Has anyone ever thought of putting the disc brake on the drive shaft as a backup? I saw that on some big truck years ago. Probably get in the way though. Yep, I think the anchor is the better plan. That or retro rockets in the front.

 

[welldigger]

Thanks for the info. Guess I could always carry a 500 pound anchor in the back & have it drop out the back with a long chain & just start grabbing at stuff to stop with.

Has anyone ever thought of putting the disc brake on the drive shaft as a backup? I saw that on some big truck years ago. Probably get in the way though. Yep, I think the anchor is the better plan. That or retro rockets in the front.

Yes pinion brakes have been done. They don't work past crawl speed.

Reason is 2 fold. The disk is way too small for a truck this size. 2 the pinion brake turns much faster than the hubs do. Which only serves to heat the brake even faster.

Remember with brakes the idea is to dissipate energy. Your vehicles brakes turn kinetic energy into heat. For your brakes to function properly they must be able to dissipate that heat.

The smaller the rotor/drum the less heat it can dissipate. The faster it turns the hotter it gets.

 

[gimpyrobb]

The smaller the rotor/drum the less heat it can dissipate. The faster it turns the hotter it gets.

To add to this, the drive line spins about 7x faster than the wheels.

 

[o1951]

If you lose the brakes, can't you just down shift and shut the motor off, letting the engine compression do the braking? QUOTE]

The only way I know of getting significant braking out of a diesel engine is with a jake brake, and you are not stopping fast with just the jake. Some over the road tractors have jakes, but I am not aware of uncle putting them on military vehicles.

 

[Floridianson]

No but the multi fuel has high enough compression. So if needed pull the engine stop and shut down the motor might help to reduce some speed.

 

[Floridianson]

There is all this talk about CO2, would putting it in 5th and stalling it not work?

Yes if you are ready and awake. If it is in low range out of gear and your finger is up you bum no it will go WOT and could be hard on clutch /trans. I still don't believe if it was running yesterday the fuel control in most cases will not be stuck tomorrow. The problem is engine sitting too long plus OP's to much hurry and does not remove shut down cover to inspect control assembly.

 

[Wolfgang the Gray]

If you lose the brakes, can't you just down shift and shut the motor off, letting the engine compression do the braking? QUOTE]

The only way I know of getting significant braking out of a diesel engine is with a jake brake, and you are not stopping fast with just the jake. Some over the road tractors have jakes, but I am not aware of uncle putting them on military vehicles.

When I was stationed in Australia, I volunteered with the local fire department and got to drive their water tanker. It had a jake brake and I thought it was pretty cool (only vehicle I ever drove that had one).

As for the runaway engine, I have been reading TM9-2320-209-10-1 and found this ominous warning:
"WARNING - If engine does not stop after you have pulled the ENG. STOP control knob out, leave the truck immediately and take cover to avoid personal injury."

I can understand that when dealing with a truck that the government owns. You can just stand back & watch the thing shred itself & nudge your buddy & say "Hehehehe, that was cool". However, with ME being the owner of the vehicle, I would definitely jump into action and try to shut the engine down to avoid costly damage. Of course, PM (Preventative Maintenance) is always better than SPR (Smoking Pile of Rubble).