Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #46  
Old 04-06-2011, 07:58 PM
funola's Avatar
Registered User
 
Join Date: May 2005
Location: NYC
Posts: 8,245
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.

__________________
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
Reply With Quote
  #47  
Old 04-06-2011, 10:14 PM
layback40's Avatar
Not Banned
 
Join Date: Nov 2009
Location: Victoria Australia - down under!!
Posts: 4,023
Quote:
Originally Posted by tomscat1 View Post
Here is a thread that was initiated by the young man's father in a different forum:
"Death of a Bimmer Lover" was the title he chose for it. Some info in there on jack stands (both homemade and commercially available).

http://forums.bimmerforums.com/forum/showthread.php?t=1625985

I hope every one takes a close look at these stands. They are what we should all be using.
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.
__________________
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
Reply With Quote
  #48  
Old 04-06-2011, 10:14 PM
Registered User
 
Join Date: Feb 2011
Posts: 182
Quote:
Originally Posted by funola View Post
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.


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.
__________________
[SIGPIC]
Tom
SE Connecticut
1975 W115 300D

visit my blog:
http://mercedesdieselrebuildingdiederich.blogspot.com/
Reply With Quote
  #49  
Old 04-06-2011, 10:54 PM
funola's Avatar
Registered User
 
Join Date: May 2005
Location: NYC
Posts: 8,245
Quote:
Originally Posted by tomscat1 View Post
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.
Sure, please do. I would like others do this test on their ratcheting jack stands to see if it behaves the same, i.e. drop to the bottom. Use one hand against the wall to help your balance on the jack stand.

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.
__________________
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
Reply With Quote
  #50  
Old 04-06-2011, 11:36 PM
Registered User
 
Join Date: Feb 2011
Posts: 182
Quote:
Originally Posted by funola View Post
Sure, please do. I would like others do this test on their ratcheting jack stands to see if it behaves the same, i.e. drop to the bottom. Use one hand against the wall to help your balance on the jack stand.

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.
I have posted this in 3 different Bmw forums that I frequent (bimmerforums)
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/
__________________
[SIGPIC]
Tom
SE Connecticut
1975 W115 300D

visit my blog:
http://mercedesdieselrebuildingdiederich.blogspot.com/
Reply With Quote
  #51  
Old 04-06-2011, 11:57 PM
Registered User
 
Join Date: Feb 2011
Posts: 182
Hey.... I just realized you are in CT also....
I am in East Lyme. Perhaps our paths will cross at some point.

__________________
[SIGPIC]
Tom
SE Connecticut
1975 W115 300D

visit my blog:
http://mercedesdieselrebuildingdiederich.blogspot.com/
Reply With Quote
  #52  
Old 04-07-2011, 12:01 AM
Registered User
 
Join Date: Jan 2002
Posts: 18,350
Quote:
Originally Posted by funola View Post
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.
I conducted a similar test with the same results. The question is how much force is required to lift that handle when a car is on top of the stand? Pretty sobering nonetheless.
__________________
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
Reply With Quote
  #53  
Old 04-07-2011, 12:08 AM
Registered User
 
Join Date: Feb 2011
Posts: 182
Quote:
Originally Posted by kerry View Post
I conducted a similar test with the same results. The question is how much force is required to lift that handle when a car is on top of the stand? Pretty sobering nonetheless.
Wow. You are exactly right. Thank you for this post.

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.
__________________
[SIGPIC]
Tom
SE Connecticut
1975 W115 300D

visit my blog:
http://mercedesdieselrebuildingdiederich.blogspot.com/
Reply With Quote
  #54  
Old 04-07-2011, 12:12 AM
vstech's Avatar
DD MOD, HVAC,MCP,Mac,GMAC
 
Join Date: Mar 2006
Location: Mount Holly, NC
Posts: 26,835
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.
__________________
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!
Reply With Quote
  #55  
Old 04-07-2011, 01:21 AM
layback40's Avatar
Not Banned
 
Join Date: Nov 2009
Location: Victoria Australia - down under!!
Posts: 4,023
Quote:
Originally Posted by vstech View Post
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.
& the dog runs past & bumps the handle or some one walks past & kicks it.

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.
__________________
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
Reply With Quote
  #56  
Old 04-07-2011, 01:35 AM
Orv's Avatar
Orv Orv is offline
Registered User
 
Join Date: Mar 2011
Posts: 698
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.
Reply With Quote
  #57  
Old 04-07-2011, 11:20 AM
funola's Avatar
Registered User
 
Join Date: May 2005
Location: NYC
Posts: 8,245
Quote:
Originally Posted by kerry View Post
I conducted a similar test with the same results. The question is how much force is required to lift that handle when a car is on top of the stand? Pretty sobering nonetheless.
It would need quite a lot of force since the handle is only 4.5" long and must be hit from underneath in an upward direction, that's a 1 in a million stars/planets/moons aligning occurence IMO.

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
Reply With Quote
  #58  
Old 04-07-2011, 11:25 AM
vstech's Avatar
DD MOD, HVAC,MCP,Mac,GMAC
 
Join Date: Mar 2006
Location: Mount Holly, NC
Posts: 26,835
oh, and most of my stands are 6 ton and 12 ton models... big honking suckers.
ME LIKEY LARGE FOOTPRINT STANDS!
__________________
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!
Reply With Quote
  #59  
Old 04-07-2011, 11:32 AM
funola's Avatar
Registered User
 
Join Date: May 2005
Location: NYC
Posts: 8,245
Quote:
Originally Posted by layback40 View Post
......

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.
I agree. I am going to stop using my ratcheting jack stands as primary for that reason. I bought 4 x 3 ton Craftsman jack stands few years ago but have not used them much and they are still shiny with no marks on the paint. I am going to see if Sears will take them back if I point out its flaws by giving them a live sobering demo.

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
Reply With Quote
  #60  
Old 04-07-2011, 12:30 PM
Orv's Avatar
Orv Orv is offline
Registered User
 
Join Date: Mar 2011
Posts: 698
Quote:
Originally Posted by funola View Post
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!!!!
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.

Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 04:31 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page