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#46
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I dug out my Craftsman ratcheting jack stand and gave it a close look and a quick test. Mine is the 3 ton and I assume the 4 ton is of simillar design. I raised it halfway, crouched, stood and balanced myself on it, reached down and yanked upward on the handle. To my surprise, it (and I) dropped all the way to the bottom! That was very sobering! Jack stand with pins will never do that! I was expecting it to catch on the next tooth on the rack but not so. The handle only needs to be raised upwards 3/4" to release the rack for it to drop. I'll try to find the owners manual and see what warnings/ instructions are provided.
With the car's weight (let's say 3000 lbs) on the jackstands, how much force is required to hit the handle at such an angle and cause it to go up 3/4"? Any mechanical engineers here want to take a stab at it? The jack release handle is 4.5" long.
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85 300D turbo pristine w 157k when purchased 161K now 83 300 D turbo 297K runs great. SOLD! 83 240D 4 spd manual- parted out then junked |
#47
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If you are good with a chain saw you can make them from a section of tree trunk, thats what I use. Once the car is on, it wont go any where!! They probably will be cheaper than metal stands. Make sure they are no higher than 3/4 of their length or width. funola, the geometry (shape) of the locking mechanism will determine how much load is required to unlock it. If you have one that had the surface of the teeth smoothed off during manufacture, it may only need the force of your little finger, if it has an over center shape, it may need a force equivalent to the weight of the car. You could always do a little experiment. Just need a backup support 1/4" lower.
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Grumpy Old Diesel Owners Club group I no longer question authority, I annoy authority. More effect, less effort.... 1967 230-6 auto parts car. rust bucket. 1980 300D now parts car 800k miles 1984 300D 500k miles 1987 250td 160k miles English import 2001 jeep turbo diesel 130k miles 1998 jeep tdi ~ followed me home. Needs a turbo. 1968 Ford F750 truck. 6-354 diesel conversion. Other toys ~J.D.,Cat & GM ~ mainly earth moving |
#48
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Very interesting post.... Thank you very much. I would like to post your results in other forums to continue to raise consciousness on the subject of safety... As well as productive discussion. Yours is a most interesting experiment, worth looking at some more, in my opinion.
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[SIGPIC] Tom SE Connecticut 1975 W115 300D visit my blog: http://mercedesdieselrebuildingdiederich.blogspot.com/ |
#49
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The fact that he was able to crash into the jack handle tells me he raised the car with a floor jack, then crawled under the car between the front wheels and placed the jack stand with the handle facing the opposite wheel. I wonder if the owners manual warn against such placements. When I place a jack stand, I always do it while crouching on the outside perimeter of the car after it's jacked up so the handle is naturally facing away from the car.
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85 300D turbo pristine w 157k when purchased 161K now 83 300 D turbo 297K runs great. SOLD! 83 240D 4 spd manual- parted out then junked |
#50
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as well as my two blogs. I don't think we can ever talk too much about safety. We mourn two fellow gear heads, dead in the last two weeks, crushed by their cars. Enough is enough. Stay safe, fellas. It can happen to you. http://mercedesdieselrebuildingdiederich.blogspot.com/ http://baurspotting.blogspot.com/
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[SIGPIC] Tom SE Connecticut 1975 W115 300D visit my blog: http://mercedesdieselrebuildingdiederich.blogspot.com/ |
#51
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Hey.... I just realized you are in CT also....
I am in East Lyme. Perhaps our paths will cross at some point.
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[SIGPIC] Tom SE Connecticut 1975 W115 300D visit my blog: http://mercedesdieselrebuildingdiederich.blogspot.com/ |
#52
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1977 300d 70k--sold 08 1985 300TD 185k+ 1984 307d 126k--sold 8/03 1985 409d 65k--sold 06 1984 300SD 315k--daughter's car 1979 300SD 122k--sold 2/11 1999 Fuso FG Expedition Camper 1993 GMC Sierra 6.5 TD 4x4 1982 Bluebird Wanderlodge CAT 3208--Sold 2/13 |
#53
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I think I will assume, based on these results, that the answer to the question of how much force is required..... I am gonna go with ..... It is less than you might think. Don't take any chances.
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[SIGPIC] Tom SE Connecticut 1975 W115 300D visit my blog: http://mercedesdieselrebuildingdiederich.blogspot.com/ |
#54
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I ALWAYS place my jackstands where the handle is facing the outside edge of the vehicle. one, it makes it easier to remove the stands from the car when job is done, and two, it keeps me from using the handle to maneuver the creeper around on the garage floor.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread "as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do! My drivers: 1987 190D 2.5Turbo 1987 190D 2.5Turbo 1987 190D 2.5-5SPEED!!! 1987 300TD 1987 300TD 1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere! |
#55
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They need some sort of pin that can go through the top & bottom 1/2 so that if the handle gets bumped they cant fall all the way. Maybe some sort of chain that holds the handle in position. What you have is a potential single contingency failure that can kill with no back up. Its like walking around with a 45 in your pocket without the safety on.
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Grumpy Old Diesel Owners Club group I no longer question authority, I annoy authority. More effect, less effort.... 1967 230-6 auto parts car. rust bucket. 1980 300D now parts car 800k miles 1984 300D 500k miles 1987 250td 160k miles English import 2001 jeep turbo diesel 130k miles 1998 jeep tdi ~ followed me home. Needs a turbo. 1968 Ford F750 truck. 6-354 diesel conversion. Other toys ~J.D.,Cat & GM ~ mainly earth moving |
#56
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When playing with this do take care to keep your fingers clear. I just smashed my fingernail pretty good playing with one of my 3-ton jack stands, 'cause I'm a clumsy idiot...fortunately I didn't really have any weight on it at the time.
Mine requires a fair bit of force to disengage under load but I suspect a sudden impact would do it. I consider this a design flaw -- by shaping the ratchet teeth differently they could have made dislodging it under load outright impossible. A pin would be the ideal safety because it would also protect you in the event the ratchet pawl failed. I'm be tempted to drill mine for pins but I'm afraid of weakening them. |
#57
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The handle is more for the ease of picking up/ positioning the jack. If you are really concerned, You can cut the handle shorter leaving just a stub making it a smaller target and also greater force required to release. I think there is more to the story of that accident in CT. He was described as a "car guy". If so, why was the oil drain bolt so tight that it sent him flying on the creeper? Why did he crawl under the car to position the jack stand instead of placing it from above? A possible explanation is that the paw (on the handle) was not seated between 2 teeths of the rack, but wedged against 1 tooth of the rack when the weight of the car was lowered and it held, then when hit, it triggered and dropped. I tried to simulate that and it was hard to do but possible. If the rack had debri in it it would make it easier.
__________________
85 300D turbo pristine w 157k when purchased 161K now 83 300 D turbo 297K runs great. SOLD! 83 240D 4 spd manual- parted out then junked |
#58
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oh, and most of my stands are 6 ton and 12 ton models... big honking suckers.
ME LIKEY LARGE FOOTPRINT STANDS!
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread "as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do! My drivers: 1987 190D 2.5Turbo 1987 190D 2.5Turbo 1987 190D 2.5-5SPEED!!! 1987 300TD 1987 300TD 1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere! |
#59
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The biggest problem I have with the ratcheting jak stands is the jack dropping to bottom if the paw releases from the rack. That can happen if the handle is raised 3/4", or if the paw cracks. NO BACK UP = DEATH!!!!
__________________
85 300D turbo pristine w 157k when purchased 161K now 83 300 D turbo 297K runs great. SOLD! 83 240D 4 spd manual- parted out then junked |
#60
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Another thought -- how short are your stands? Even with mine in their lowest position I have to lift the car pretty high, almost to the full extension of my floor jack, to get them underneath; I rarely have them extended more than one or two teeth. If the stand falls to the bottom I'll probably need to change my pants, but it's not likely to crush me. I'd be more worried about the stand tipping over.
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