Close Call

[J. Huber]

This is a fairly serious one, folks.

Today, the sun was out again and I decided to remove the hard-top for my first top-down drive of '08. I have a manually controlled Fritzi-Hooker hoist. I've had it a couple years now. Anyway, I lifted the top up as usual, taking my time and getting it all secure.

Once it was up, I pulled car out of garage (and out of the way). I then started to lower top to the ground because I wanted to assess the rear wood, rubber seals, etc. Then it happened. About 2 feet from the ground, one strap popped, then another, and another. I sort of guided it to the ground but it was going anyway. Slam. Not a good sight.

Apparently the plastic clips that hold the straps secure simply broke. Somehow, I lucked out, the damage is minimal. But had it happened literally one minute earlier, the car would have been underneath! That would have been really bad.

Moreover, I "used to" store the top up on the hoist, above the car. May be a while before that happens again...

Have a look. (excuse the messy garage!)

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Here are the clips. At least 4 snapped as it went.

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James
63 230SL

----------------
Response here because of error message!

Well Hauser. Yes -- I consider myself really lucky. It happened so fast and could have happened earlier (or anytime all last year for that matter) -- as it dangled over the car. yikes.

I have thought about the metal ones. I would likely have to have an upholstery guy refit them since the straps are stitched around them. Ironically, the hoist itself seems pretty well made -- those buckles are the only plastic on there I think. The old " only as strong as the weakest link" seems to apply here. They are really just a little larger than what you see on a backpack. And who hasn't broken one of those?

And Joe, your points are well-taken but I would think two years is not much of a life for a product such as this. Granted, my garage gets a bit cold in the winter -- but these clips have not seen much of the elements, really. Bottom line, I just want others to be cautious.

[thelews]

The exact same thing happened to me with the top maybe 2 -5 inches above the car, depending front or back.  Two of the plastic buckles broke.  Surprisingly, no damage, top must have come back down on all rubber pieces.  I ended up using webbing with ratchets rated to 300+ lbs instead and still didn't like it up in the air.  Carried it into the basement with my son.

John
1967 Early 250 SL Red/Caviar, Manual

[ja17]

Plastic degrades with age, mostly from the UV from sunlight. Chemicals also will alter the plastic making it weaker and brittle as Michael S can tell you in much more detail! Plastic things which were once supple, clear and free of discoloration become brittle and discolored.

Consider the plastic parts on your Pagoda; brake booster line, brake fluid resevour, convertible soft top rear window, horn pad, etc.

Joe Alexander
Blacklick, Ohio

[thelews]

quote:Originally posted by ja17

Plastic degrades with age, mostly from the UV from sunlight. Chemicals also will alter the plastic making it weaker and brittle as Michael S can tell you in much more detail! Plastic things which were once supple, clear and free of discoloration become brittle and discolored.

Mine were brand new.

John
1967 Early 250 SL Red/Caviar, Manual

[hauser]

Unfortunate that this happened but you lucked out.  Could have been much worse.  I wonder if you can replace these buckles with metal ones?  Do you intend on contacting the manufacturer?  perhaps this has happened in the past and the company may have a solution to this failure of hardware.

1969 280sl 5 spd
Gainesville, Fl.

[hands_aus]

James,
You were lucky.

I made two slings out of seat belt webbing threaded through solid steel rings and tied in grannysmith knots.
Once they are set up for the job no adjustment of length is needed and no slip of the knots is possible.

I use a boat winch mounted on the inside garage wall, well above head height.

To lower or raise the hard top I have to stand on a lump of 4" square wood and reach up.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[glennard]

Plastic!!  Remember the 'Challenger' o-rings.  Been contemplating the design of a 'hardtop lift' for the past couple of years.  Foremost was the security of the lift-not dropping it during lift, storage, etc.  Even a two person manual lift has resulted in scratches.  Does the PSG(Pagoda SL Group) have a solution to the problem?   Some of us would like the option of an easy hard top on/off many times each year for up and down Northern weather.

[Mike Hughes]

The plastic buckles look suspiciously just like the ones that broke the very first time I used my brand new hardtop hoist to install the hardtop on my 230SL.  The supplier refused to replace either the plastic buckles, or the strap set, when called, suggesting that I didn't attach the straps to the hardtop correctly.  As a result, my hardtop has been on the car for the last two years as my wife is unwilling to try to help removing it after she almost dropped it on the decklid the one and only time we tried to remove it by hand.

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

[thelews]

quote:Originally posted by Mike Hughes

 As a result, my hardtop has been on the car for the last two years as my wife is unwilling to try to help removing it after she almost dropped it on the decklid the one and only time we tried to remove it by hand.

Instead of plastic buckles, after mine broke, I bought a set of four 1" wide webbing straps with ratchets rated to 300+ lbs. each from the local big box hardware store for about $14.  These were much more secure and allowed for adjustment after liftoff or prior to.  I cut the sewn in hooks off the ends and threaded them through my top holding brackets.  The epiphany came after my first close call...I took the top off the car by hand with my wife, set it down, moved the car away and then placed the top under the hoisting mechanism.  Better 1 damaged top than both the top and car should another accident occur.  

John
1967 Early 250 SL Red/Caviar, Manual

[seattle_Jerry]

Even if it was "new", there is no guaranty how long the parts sat on the shelf prior to sale.

The seat belt material is way overkill, the plastic is just the opposite. I would think that bulk rock climbing rope or similar would be more than sufficient.

Injection molders use a percentage of recycled content in nearly everything they make. Think of a model kit and all the extra plastic that the parts are attached to. The molder regrinds all the extras and reuses it. If they use too high a percentage, the parts get brittle.

A second cause for failure in parts like that are "weld" or "knit" lines. The plastic flows around the buckle shape from both directions and where the flow meets there is a hairline weld that is a weak point.

1967 230SL Havana Brown Auto with A/C

[DavidAPease]

James,

Thank you for bringing this up.  My top is currently on the car, but after reading your post I went out to the garage and found that both buckles on one strap were close to failing!  (The others look fine...)

John,

How about a photo of your modified straps?  Thanks!

-David Pease
'66 French 230SL

[Mike Hughes]

I'd like to see a photo of John's adjustable strap set up, too!

- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havanna Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

[thelews]

Here are pictures of the setup with the webbing and the plastic buckles, two of which broke. I did not take a picture of the top all set up with the ratchets as I decided against the whole setup and put it in my basement.  Ratcheted webbing shown...cut hook off one end and looped through the black top holding (car carrier) bracket (Sears Automotive...see package).  Plenty of room for adjustment.  Sewn in hooks on other end of ratchet hook into center ring under the lifting eye bolt.  As the top raises, ratcheting can be done to further balance and level off the top.

























John
1967 Early 250 SL Red/Caviar, Manual

[hauser]

How does the expensive EZ Top compare?  Does it also have these plastic parts?

1969 280sl 5 spd
Gainesville, Fl.

[J. Huber]

Just a follow up. I contacted the company and they responded quickly and professionally. (of course, I was not suing for a new hardtop!). Anyway, the rep said buckles have broken before but never has a top fallen. They sent me a replacement strapping mechanism (basically the same parts up to the pulley: straps, buckles, and mounting hooks). Problem is, the buckles are still plastic. He said they have tried to get supplier to change to metal but they won't. They also want me to send back my old ones so they can "analyze" the failure. I will in the name of science.

However, I am not likely to use the hoist as is unless I have a back-up set of straps somehow in place.

Bob's (hand aus) idea of a nice knot at the loose end of the strap is a good one. That may have held the straps in place when the buckles went. As it was, they just slithered through the strap buckles (with 108 pounds of dead weight speeding things up) [!]

James
63 230SL

[thelews]

How about a threading plate like this?

http://www.berkeleypoint.com/products/hardware/S0215-0025.html

John
1967 Early 250 SL Red/Caviar, Manual

[waqas]

quote:Originally posted by J. Huber

They also want me to send back my old ones so they can "analyze" the failure. I will in the name of science.

Maybe I'm a cynic, but I suspect they just want to destroy the evidence in case you decide to sue them at a later date.

Waqas in Austin, Texas

[J. Huber]

Hi Waqas, it could be but that's when I call you and God and the rest of the Pagoda world as witnesses.

James
63 230SL

[TheEngineer]

May I bring up an analysis of the design: When you have webbing almost horizontal and you pull in the middle, the force on the webbing, in tension, is very high. Fortunately, the attachment point lifts a little and that reduces the tension. If it wouldn't the force on the webbing would be infinite. It's a matter of geometry. If you want to lift a structure like the hardtop, you need a beam stretching across and hooks dangling from the ends.

'69 280SL,Signal Red,Automatic,retired engineer, West-Seattle,WA

[thelews]

quote:Originally posted by theengineer

May I bring up an analysis of the design: When you have webbing almost horizontal and you pull in the middle, the force on the webbing, in tension, is very high. Fortunately, the attachment point lifts a little and that reduces the tension. If it wouldn't the force on the webbing would be infinite. It's a matter of geometry. If you want to lift a structure like the hardtop, you need a beam stretching across and hooks dangling from the ends.

'69 280SL,Signal Red,Automatic,retired engineer, West-Seattle,WA

I get it!

John
1967 Early 250 SL Red/Caviar, Manual

[J. Huber]

I do too -- that made perfect sense (even to me!). Thanks Professor Engineer!

BTW, has anyone ever used or seen a hoist like this one here? It came with the car (1979!) but I never used it. Mainly because I did not have the ability to actually hoist the top (which of course, I now do with the strapped version under fire here).



James
63 230SL

[DavidAPease]

For what it's worth, I ordered 8 of these:

http://www.strapworks.com/Metal_Slides_p/ms-f.htm

at a whopping $.45 each in the correct 2-inch width. I exchanged email with a very friendly person there who feels that the squared-off edges of the metal slide will grip and hold the strap under tension just fine.  I'll report in after I install them.

-David Pease
'66 French 230SL

[psmith]

I can't remember the name of my lift, but it has a horizontal bar and clamps onto the gutters like a luggage rack.  There are straps that go fore and aft, but they are only there to make it less tippy.  







Pete S.

[mdsalemi]

quote:
Maybe I'm a cynic, but I suspect they just want to destroy the evidence in case you decide to sue them at a later date.

Waqas in Austin, Texas

Don't be so cynical, Waqas...

I had serious rust and corrosion issues in some STAINLESS STEEL solenoid valves from Grainger.  I took the issue up past the local Grainger, past Grainger's Corporate Customer Service, past their Product Manager and onto the manufacturer, Emerson Flow Controls.

They asked for the valves back, and they did indeed send them out for failure analysis and received back from an independent firm a detailed metallurgical analysis which they did indeed share with me.

The manufacturer bypassed all of Grainger in the search for the answer; replaced the one valve that had failed last year.  As the units were used in a freeze-control system, since they had not got to the bottom of the problem by November, sent me another 4 so I could begin the freeze-protection season with new ones.

Sometimes lawyers are NOT involved, only problem solving!

Michael Salemi
1969 280SL
Signal Red 568G w/Black Leather (Restored)
President, International Stars Section
Mercedes-Benz Club of America

[J. Huber]

Hi David. Those look good. I may be right behind you. The problem I see is on the original straps, the buckles were sewn in (see below). Then this short strap is added to the longer one for adjusting. Are you planning to bypass the sewn in concept and just thread the 2 inch strap through? Or get them sewn in? Make any sense?



Download Attachment: Slide1.JPG
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James
63 230SL