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Author Topic: Run Away Detroit  (Read 4508 times)
eagle19952
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« on: July 16, 2015, 07:24:47 PM »

sad day for this motor Sad Might wanna turn the volume down Smiley

https://video-atl1-1.xx.fbcdn.net/hvideo-xfp1/v/l/t42.1790-2/11183976_1139709659378843_1243429475_n.mp4?efg=eyJybHIiOjU3MiwicmxhIjoxMDU2fQ%3D%3D&rl=572&vabr=318&oh=797d7eac9905b2e6251360d498e4b90e&oe=55A88BC1
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Donald PH
1978 Model 05 Eagle w/Torsilastic Suspension,8V71 N, DD, Allison on 24.5's 12kw Kubota.
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« Reply #1 on: July 16, 2015, 07:43:17 PM »

Yep ... very sad.  Also very expensive.  And that is why, before the dawn of time, our old beloved DD 2 strokes (the early ones) had that blower intake flapper thingie that could be slammed down with suction and spring pressure shutting off nearly all the air.  Better to blow some seals than toast the entire engine.  I was told the world record for a run a way Detroit, (probably without the shut down thingie) was about 4500 rpm?  Then the valves float?  Dunno fur sures.  HB

That also leads into a very expensive interesting story which shall be saved for later. Smiley
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TomC
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« Reply #2 on: July 16, 2015, 09:18:00 PM »

That's what happens when you blow a turbo and the engine runs away on the engine oil. Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Iceni John
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« Reply #3 on: July 16, 2015, 11:04:50 PM »

If you turned on the Jakes, would that be enough to stop a runaway, at least in a 2-stroke?   If the engine's got no compression, surely the oil can't combust in the cylinders?   I don't know if this plan would work with a 4-stroke because Suck Squeeze Bang Blow occurs over twice the number of piston movements.   If the Jake plan works, it could be better than blocking the inlet or firing a CO2 extinguisher into the intake or whatever other ways.

Just an idea.   (I thought of it in the shower  -  all my best/worst thinking happens in the shower.)

John
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1990 Crown 2R-40N-552 (the Super II):  6V92TAC / DDEC II / Jake,  HT740.     Hecho en Chino.
2kW of tiltable solar on the roof.
Behind the Orange Curtain, SoCal.
IMABUSBOY
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« Reply #4 on: July 17, 2015, 07:34:29 AM »

The old coal truck I used to drive (GM 5 over 4 tranny) had a "T" handle that was a compression release. You  pull it so that there was no compression on the engine and when the starter was up to speed, you push it in to start the engine. The only way to shut the engine down was to pull the T handle, releasing the engine compression. Why is there not a compression release on these buses? just thinking Danny
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« Reply #5 on: July 17, 2015, 08:06:15 AM »

If you turned on the Jakes on a runaway engine past 2300 RPM (from turbo oil) you would stop the engine  but bend half the valves (the ones the Jake are holding open).  If you could stand the noise the best thing is to cut off the air supply, but that would take time and nerves of steel.  Runaway Detroits make my heart rate explode-- this is known from a few incidents. 

--Geoff

If you turned on the Jakes, would that be enough to stop a runaway, at least in a 2-stroke?   If the engine's got no compression, surely the oil can't combust in the cylinders?   I don't know if this plan would work with a 4-stroke because Suck Squeeze Bang Blow occurs over twice the number of piston movements.   If the Jake plan works, it could be better than blocking the inlet or firing a CO2 extinguisher into the intake or whatever other ways.

Just an idea.   (I thought of it in the shower  -  all my best/worst thinking happens in the shower.)

John
« Last Edit: July 17, 2015, 08:12:15 AM by Geoff » Logged

Geoff
'82 RTS AZ
Scott & Heather
Scott & Heather's buses: MCI-9 & MCI-102
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« Reply #6 on: July 17, 2015, 09:08:04 AM »

I cut a hole in the side of our MCI 9 and stuck stainless mesh over it so I could pull it off and slap a clipboard over the intake rubber grommet.
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Scott & Heather
1984 MCI 9 6V92-turbo with 9 inch roof raise (SOLD)
1992 MCI 102C3 8v92-turbo with 8 inch roof raise CURRENT HOME
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eagle19952
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« Reply #7 on: July 17, 2015, 09:51:35 AM »

I cut a hole in the side of our MCI 9 and stuck stainless mesh over it so I could pull it off and slap a clipboard over the intake rubber grommet.

in this runaway scenario, a clip board could possibly/likely be ingested also...that's why airhorn flappers were steel Smiley
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Donald PH
1978 Model 05 Eagle w/Torsilastic Suspension,8V71 N, DD, Allison on 24.5's 12kw Kubota.
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« Reply #8 on: July 17, 2015, 03:07:39 PM »

Why would the valves bend?  I do not understand. HB
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Iceni John
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« Reply #9 on: July 17, 2015, 03:20:59 PM »

If you turned on the Jakes on a runaway engine past 2300 RPM (from turbo oil) you would stop the engine  but bend half the valves (the ones the Jake are holding open).  If you could stand the noise the best thing is to cut off the air supply, but that would take time and nerves of steel.  Runaway Detroits make my heart rate explode-- this is known from a few incidents. 

--Geoff

On second thoughts, turning on the Jakes may not work, because they should only work when in gear or lockup and when at No Fuel, and when the Ignition run switch is on.  If the Jakes had an extra switch to send power in an emergency to their solenoids regardless of the usual operating parameters, even with the Ignition turned off, that could stop the engine just like the old Cummins compression release, and the risk of bending half the exhaust valves is better than definitely trashing the whole engine!   Would the valves bend because they are floating open at those high revs?

John
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1990 Crown 2R-40N-552 (the Super II):  6V92TAC / DDEC II / Jake,  HT740.     Hecho en Chino.
2kW of tiltable solar on the roof.
Behind the Orange Curtain, SoCal.
Scott & Heather
Scott & Heather's buses: MCI-9 & MCI-102
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« Reply #10 on: July 19, 2015, 05:56:03 AM »

Aha then! My clipboard shalt be made of steel!


Sent from my iPhone using Tapatalk
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Scott & Heather
1984 MCI 9 6V92-turbo with 9 inch roof raise (SOLD)
1992 MCI 102C3 8v92-turbo with 8 inch roof raise CURRENT HOME
Click link for 900 photos of our 1st bus conversion:
https://goo.gl/photos/GVtNRniG2RBXPuXW9
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« Reply #11 on: July 19, 2015, 06:21:40 AM »

On the video, don't understand why the guy didn't just stick it in gear and let out the clutch? Course you do some non thinking things in emergencies. Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #12 on: July 19, 2015, 09:22:57 AM »

On second thoughts, turning on the Jakes may not work, because they should only work when in gear or lockup and when at No Fuel, and when the Ignition run switch is on.  If the Jakes had an extra switch to send power in an emergency to their solenoids regardless of the usual operating parameters, even with the Ignition turned off, that could stop the engine just like the old Cummins compression release, and the risk of bending half the exhaust valves is better than definitely trashing the whole engine!   Would the valves bend because they are floating open at those high revs?

John

Lets see, if the Detroit is a "runaway", and is running on turbo oil, then you are not going to be pushing on the throttle, so the Jake micro switch would be in the idle position so the Jakes would come on at high speed.  And if the Jakes come on at high speed, they are holding two valves open which would make them kiss the pistons.  And yes, you can even make the valves hit the pistons by over revving the engine (like coasting down a hill in too low a gear). 

--Geoff
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Geoff
'82 RTS AZ
eagle19952
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« Reply #13 on: July 19, 2015, 09:52:36 AM »

Aha then! My clipboard shalt be made of steel!


Sent from my iPhone using Tapatalk


the aluminium ones with the folding cover work very well too...

and will look very
professional doing
either job Smiley

i prefer this one... http://www.amazon.com/Saunders-10519-Recycled-Aluminum-Snapak/dp/B0007UO4OQ/ref=sr_1_20?s=office-products&ie=UTF8&qid=1437326064&sr=1-20&keywords=Aluminum++Clipboard

PS cut and pasted for your conveniance and --- --- ----'s irritation... Grin
« Last Edit: July 19, 2015, 09:58:11 AM by eagle19952 » Logged

Donald PH
1978 Model 05 Eagle w/Torsilastic Suspension,8V71 N, DD, Allison on 24.5's 12kw Kubota.
luvrbus
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« Reply #14 on: July 19, 2015, 10:36:12 AM »

All diesel engines will runaway I have seen my share of Cummins and Cat engines destroy their self,worst I ever saw was a JT Cummins mounted vertical on a pump we dodged flying parts for 10 minutes when it got a dose of natural gas   
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