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How do you blow up an engine while towing a vehicle?

GunNutGunNut Posts: 7,642 Senior Member
Leave transmission in gear in 4L and take off.  According to the article it probably revved up to 50,000 rpm when it gave up and exploded.

https://jalopnik.com/jeep-wrangler-engine-explodes-after-owner-tows-vehicle-1846493328?utm_campaign=Jalopnik&utm_content=16160 05862&utm_medium=SocialMarketing&utm_source=facebo ok


Old West Saying: God created men, but Col. Sam Colt made them equal.

General George Patton:  “Watch what people are cynical about, and one can often discover what they lack.”

Replies

  • HappySquidHappySquid Member Posts: 415 Member
  • Some_MookSome_Mook Posts: 471 Member
    Haven't read the link you posted, but I saw the official engineering report on the incident.  The torque multiplication of the transfer case being in low range is pretty extreme, which is why when you are actually driving a vehicle in low range, your engine speed is pretty high relative to the vehicle speed.  With the engine RUNNING, the PCM will limit the RPM.  With the engine not running, the PCM is out of the picture and dragging the thing behind a pusher diesel motor home on the freeway is going to do some damage.

    Needless to say, there was no offer of Factory assistance on this one.

    If you want to see scary, look for pictures of the amount of damage an exploding Cardan Joint on a front propeller shaft can do to a Heavy Duty RAM truck.  No warranty if the failure is the result of failing to regularly lubricate the joint.  Tends to total the truck when they let go on the highway. 
    "If there must be trouble, let it be in my day, that my child may have peace." - Thomas Paine
    "I know my place in the world and it ain’t standing next to Jerry Miculek" - Zee
  • GunNutGunNut Posts: 7,642 Senior Member
    Some_Mook said:
    Haven't read the link you posted, but I saw the official engineering report on the incident.  The torque multiplication of the transfer case being in low range is pretty extreme, which is why when you are actually driving a vehicle in low range, your engine speed is pretty high relative to the vehicle speed.  With the engine RUNNING, the PCM will limit the RPM.  With the engine not running, the PCM is out of the picture and dragging the thing behind a pusher diesel motor home on the freeway is going to do some damage.

    Needless to say, there was no offer of Factory assistance on this one.

    If you want to see scary, look for pictures of the amount of damage an exploding Cardan Joint on a front propeller shaft can do to a Heavy Duty RAM truck.  No warranty if the failure is the result of failing to regularly lubricate the joint.  Tends to total the truck when they let go on the highway. 
    I'm going to have to google that one, sounds crazy!!!
    Old West Saying: God created men, but Col. Sam Colt made them equal.

    General George Patton:  “Watch what people are cynical about, and one can often discover what they lack.”

  • Some_MookSome_Mook Posts: 471 Member
    My wife and I enjoy watching the Marvel Avengers movies.  Every time I watch the Hulk whap Loki back and forth against the ground, I laugh.  But it is a pretty good image of what a heavy, spinning propeller shaft would look like beating everything within reach around it to death.
    "If there must be trouble, let it be in my day, that my child may have peace." - Thomas Paine
    "I know my place in the world and it ain’t standing next to Jerry Miculek" - Zee
  • GunNutGunNut Posts: 7,642 Senior Member
    Some_Mook said:
    My wife and I enjoy watching the Marvel Avengers movies.  Every time I watch the Hulk whap Loki back and forth against the ground, I laugh.  But it is a pretty good image of what a heavy, spinning propeller shaft would look like beating everything within reach around it to death.
    DAMN!!!  Oh and I love those movies too.  Good visual  :D
    Old West Saying: God created men, but Col. Sam Colt made them equal.

    General George Patton:  “Watch what people are cynical about, and one can often discover what they lack.”

  • zorbazorba Senior Member Posts: 24,613 Senior Member
    The grenaded Jeep has been the talk of the town on the Jeep forum I'm on. What I don't understand is why the tires just didn't drag instead of the drive train turning what with that huge gear reduction - but obviously they didn't!
    -Zorba, "The Veiled Male"

    "If you get it and didn't work for it, someone else worked for it and didn't get it..."
  • Some_MookSome_Mook Posts: 471 Member
    zorba said:
    The grenaded Jeep has been the talk of the town on the Jeep forum I'm on. What I don't understand is why the tires just didn't drag instead of the drive train turning what with that huge gear reduction - but obviously they didn't!
    The engine compression will offer some resistance to turning, but think about it - you can turn an engine over by hand with a socket and ratchet.  The engine compression would have been quite easy for the co-efficient of friction between the tires and the pavement to overcome and turn over the engine at a high RPM with the added leverage that the torque reduction of the transmission and the transfer case afforded.  Once the engine bearings got so hot that the rods began to seize, the breakage of hard parts and the torque drag from the engine being destroyed reaching enough resistance to drag the tires reached a zenith about the same time. 

    This happened while being towed at highway speeds by a large and powerful motor home, with a blissfully inattentive driver (who quite obviously possessed more dollars than sense.)
    "If there must be trouble, let it be in my day, that my child may have peace." - Thomas Paine
    "I know my place in the world and it ain’t standing next to Jerry Miculek" - Zee
  • Make_My_DayMake_My_Day Senior Member Posts: 7,865 Senior Member
    50K RPM??? Yeah right. That engine probably peaks at about 6000 or 6500.
    JOE MCCARTHY WAS RIGHT:
    THE DEMOCRATS ARE THE NEW COMMUNISTS!
  • mitdr774mitdr774 Member Posts: 1,582 Senior Member
    If the engine is driven by something other than controlled internal combustion it will unhappily spin well above its rated max RPM.  That is the case here.
  • Make_My_DayMake_My_Day Senior Member Posts: 7,865 Senior Member
    Maybe, but I don't think 50K is possible under any circumstances. How did they even measure that while in operation? Most automotive tachometers don't even read over 8K RPM unless it's a race car.
    JOE MCCARTHY WAS RIGHT:
    THE DEMOCRATS ARE THE NEW COMMUNISTS!
  • Some_MookSome_Mook Posts: 471 Member
    edited May 10 #12
    Do the math.  The engine was NOT running.  The engine crankshaft was being rotated by the fact that the tires were spinning as the vehicle was being towed and the driveline was coupled to the crankshaft through the clutch.  The excessive RPM of the crankshaft was being caused by the ratios of the gearsets (rear differential ratio + transmission gear ratio + transfer case gear ratio).  The failure was a result of the heat that was being generated by the friction of the moving parts that were being rotated far faster than design intent.
    "If there must be trouble, let it be in my day, that my child may have peace." - Thomas Paine
    "I know my place in the world and it ain’t standing next to Jerry Miculek" - Zee
  • Johnny rebJohnny reb Member Posts: 700 Senior Member
    Maybe, but I don't think 50K is possible under any circumstances. How did they even measure that while in operation? Most automotive tachometers don't even read over 8K RPM unless it's a race car.
    The mechanics at the dealership said the jeep was in 4lo and in 1st gear.
    If that is the case that’s where there getting numbers of over 50,000 rpm.
    The Rubicon comes with 4.10:1 axle ratio and a 4:1 transfer case low range ratio.
    With 1st gear having a 5.13:1 ratio the crawl ratio is 84.13:1 which spins the engine 84.13 times faster than the rear wheels. They assumed a tow speed of 60mph with the stock tires rated to turn 645 revolutions per mile. The crawl ratio of 84.13:1 the engine spins 84.13 times as fast as the wheels. 645 x 84.13= 54,263.85 RPM.
  • Make_My_DayMake_My_Day Senior Member Posts: 7,865 Senior Member
    I guess I didn't read enough of the article to form a logical opinion. I forgot that it said the vehicle was being towed, and just focused on the 50K RPM's. The last 2 comments clarify the situation. Thanks.
    JOE MCCARTHY WAS RIGHT:
    THE DEMOCRATS ARE THE NEW COMMUNISTS!
  • GunNutGunNut Posts: 7,642 Senior Member
    I guess I didn't read enough of the article to form a logical opinion. I forgot that it said the vehicle was being towed, and just focused on the 50K RPM's. The last 2 comments clarify the situation. Thanks.
    Oh yeah, there is NO way this engine would have ever gotten to 50k RPMs under power.  I think the highest I've ever read someone getting a car engine revving to was somewhere in the teens?

    Old West Saying: God created men, but Col. Sam Colt made them equal.

    General George Patton:  “Watch what people are cynical about, and one can often discover what they lack.”

  • mitdr774mitdr774 Member Posts: 1,582 Senior Member
    Even the old F1 engines didnt really get much over 20k if I recall correctly.  A handful of sportbike engines have knocked on the door of 20k (mostly very small displacement engines).  I cant think of any reciprocating 4 stroke engine that would survive 50k RPM.  That would make some crazy sounds if it did hold together though.
  • GunNutGunNut Posts: 7,642 Senior Member
    I think I remember reading that someone could tune the old Rotary Wankel Engines (Mazda?) to do some crazy RPMs.  But I really don't remember the specifics so it would be a disservice to even guess.  

    Old West Saying: God created men, but Col. Sam Colt made them equal.

    General George Patton:  “Watch what people are cynical about, and one can often discover what they lack.”

  • waipapa13waipapa13 Senior Member Posts: 893 Senior Member
    GunNut said:
    I think I remember reading that someone could tune the old Rotary Wankel Engines (Mazda?) to do some crazy RPMs.  But I really don't remember the specifics so it would be a disservice to even guess.  

    Yup, early teens iirc, but like yourself it's been a long while. My old man had an RX-7 in the '80's, I grew up hearing about stories about it.
  • knitepoetknitepoet Senior Member Posts: 22,240 Senior Member
    Did a little research... The first Wankel prototype rotary engine, model DKM, could turn up to 17,000 RPM. Production models could run at 10K
    Seven Habits of Highly Effective Pirates, Rule #37: There is no “overkill”. There is only “open fire” and “I need to reload”.


  • GunNutGunNut Posts: 7,642 Senior Member
    knitepoet said:
    Did a little research... The first Wankel prototype rotary engine, model DKM, could turn up to 17,000 RPM. Production models could run at 10K
    Yeah I knew it was some crazy numbers.  BTW the V6 in the Jeep redlines at 6,500.  I think that’s higher than any other 6 cylinder I’ve ever owned.
    Old West Saying: God created men, but Col. Sam Colt made them equal.

    General George Patton:  “Watch what people are cynical about, and one can often discover what they lack.”

  • zorbazorba Senior Member Posts: 24,613 Senior Member
    If you want high RPMs, run a steam turbine!
    -Zorba, "The Veiled Male"

    "If you get it and didn't work for it, someone else worked for it and didn't get it..."
  • Lonewolf-PeruLonewolf-Peru Member Posts: 624 Senior Member
    I was checking the stats of a model plane jet engine (jetcat p20-sx). It can
    reach 5.25 pounds of thrust at 245000 rpm 
  • mitdr774mitdr774 Member Posts: 1,582 Senior Member
    GunNut said:

    Yeah I knew it was some crazy numbers.  BTW the V6 in the Jeep redlines at 6,500.  I think that’s higher than any other 6 cylinder I’ve ever owned.
    My Colorado has a LGZ 3.6L V6 in it.  Rated at 308 HP at 6800 RPM, and 275 LB-FT at 4000 RPM.  For a truck, its fairly quick in my opinion.
  • GunNutGunNut Posts: 7,642 Senior Member
    mitdr774 said:
    GunNut said:

    Yeah I knew it was some crazy numbers.  BTW the V6 in the Jeep redlines at 6,500.  I think that’s higher than any other 6 cylinder I’ve ever owned.
    My Colorado has a LGZ 3.6L V6 in it.  Rated at 308 HP at 6800 RPM, and 275 LB-FT at 4000 RPM.  For a truck, its fairly quick in my opinion.
    That’s pretty cool.  The last 6 I owned was the old Wrangler in-line 6.  Not a zoomer but it did what it was supposed to.  My cousins just bought a dodge with a six in it and he tows a 22’ center console Grady White with it no problems.  They’ve come a looooong way!
    Old West Saying: God created men, but Col. Sam Colt made them equal.

    General George Patton:  “Watch what people are cynical about, and one can often discover what they lack.”

  • zorbazorba Senior Member Posts: 24,613 Senior Member
    GunNut said:
    mitdr774 said:
    GunNut said:

    Yeah I knew it was some crazy numbers.  BTW the V6 in the Jeep redlines at 6,500.  I think that’s higher than any other 6 cylinder I’ve ever owned.
    My Colorado has a LGZ 3.6L V6 in it.  Rated at 308 HP at 6800 RPM, and 275 LB-FT at 4000 RPM.  For a truck, its fairly quick in my opinion.
    That’s pretty cool.  The last 6 I owned was the old Wrangler in-line 6.  Not a zoomer but it did what it was supposed to.  My cousins just bought a dodge with a six in it and he tows a 22’ center console Grady White with it no problems.  They’ve come a looooong way!
    I'm loving this Wrangler in-line 6 - the first straight 6 I've ever owned. Its not my beloved GMC Big Block V6, but it holds its own and is smoo-ooo-oooth!
    -Zorba, "The Veiled Male"

    "If you get it and didn't work for it, someone else worked for it and didn't get it..."
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