US Delivered ESs have an "Overbite"!

Feb 2023 R. Kwas [Comments Added]

Reference Information
    Oil-filled Impact Absorbing Bumper Mount
    ...Some Examples of Overbite

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Bureaucrats at the US DOT mandated a 5mph bumper from '72 on (of course, it would be nice if they accompanied this with a standardization of bumper heights at the same time, which they didn't, so OK if you hit another ES, but it's much more likely you make contact with a vehicle with a bumper at some other level, so why bother, other than of course enacting some feel-good regulation...).  Volvo complied with this requirement on the 1800 model, by replacing the earlier flat iron bumper mounts with energy absorbing tubular mounts.  These Energy Absorbers are of course much bigger in cross-section, so require a much bigger pass-through at the front and rear body valances. 

An owner asked about curing the resulting "look".   


David Lau picture used with his kind permission. 

My answer to "Overbite" question by David Lau:  How do we cure the US73 overbite?

The "Overbite" [I would call it an underbite...I'm not a dentist...but I have played doctor a time or two!] protrusion is a result of the federally mandated 5mph bumper shocks (and useless like teets on a bull since it would ONLY do anything IF it hit another car whose bumper was at the same exact height...but those same DOT idiots STILL haven't standardized bumper heights among vehicles, so that is way less than likely!).

If you feel strongly about loosing the overbite (understandable since it does look pretty stupid, and is unlikely to be of any benefit in a crash, you could drill into the shocks, allow the oil to drain out (don't know if it's under pressure when at rest and not compressed by a crash...someone who has practical knowledge can chime in!), collapse them (measure twice to confirm how much length can be lost before bumpers make contact with body!) then weld them at the preferred collapsed length...

I was given to understand they were filled with oil (I know that's what some 5mph bumpers in the US had, but not certain about the ES types)...maybe Fran, who got hit by another car with same bumper height, (but purely luckily!) can chime in if they puked out an oil filling, which is how they dissipated the compression energy. I agree demounting, compressing, and remounting the energy absorber shocks would be my preferred solution...that way, the position would still be correct. " 

I would think '72 brackets of flat stock would be the Eurobrackets...and your '73 has the tubular cross-section shock absorbers. The question I would have is was the hole through the valance the same for both, with the rubber boot taking up the extra space when Eurobrackets were fitted.

I do not have the answer to that question...maybe an owner of a factory unmolested car with European brackets can take a picture of the rubber boot and/or hole in the valance.

Paul Cassell then posted:  "... I can confirm that it does indeed have rather large rectangular openings in the front valance where the irons pass through to the chassis legs. Equally large rubber grommets are in place with just a 'slot' towards the edge to accommodate the flat steel irons. I've always assumed that it was easier for Volvo to produce a front valance to accommodate the needs of their largest ES market (USA) for 73 model year cars and just disguise the hole intended to have those unsightly impact-absorbing dampers poking through for their European and UK customers by filling them with a rubber blanking grommet! ..." 

...and followed up with a "photo of the UK front bumper iron aperture and grommet set up on my 73 ES,"


European delivered ES with non-energy absorbing bumper mounts.  Paul Cassell pic used with his kind permission.

Pictures of the Energy Absorber Bumper mounts covered by Rubber Boots.

 

 

Of course, as poster Ola Øra notes, "The solution would be to convert bumper and brackets to the European version. This is my -72 ES, imported from Sweden where it was sold as new." 


Ola Øra picture, of his Euro delivered ES, also with early flat-stock bumper mounts from the factory, picture used with his kind permission. 

My response:  "If you changed to Eurobrackets on bumpers, from much bigger energy absorbers protruding through the lower valance, I expect you also have to close the remaining hole down..."  [it looks from Paul's pic, that the factory rubber boots do this.]

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Reference Information:

US delivered ES with energy absorbing bumper mount boots are almost a full 3 inches wide, and that is about how much further they also protrude.  They don't only cover the big rectangular hole in front valance, but contain the tubular energy absorbing structure.  It looks like one could loose about 3" of protrusion before bumpers would contact the Parking/Directional Light Housing.    

 
US Bumper Mount.

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Some relevant frame captures from GCP.se site: 

Early Bumper Configuration:  


There are early and late chassis variations, and Front and Rear "Bumper Guards" Items 14 and 42 are different sized.

 

US Bumper (Energy Absorber) Configuration: 


It looks like the rears have no Rubber Boots, while the fronts have a Righty and Lefty (Item 20)!


 

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Oil-filled Impact Absorbing Bumper Mount: 

My comments to Thread:  1800list@groups.io | 1973 shock absorbing bumper operation

" I recall seeing, in the immediate aftermath of a rear-ender accident in the late 70s/80s time-period, where a filled energy-absorber bumper-mount (definitely on not an 1800!) had expelled its (oil appearing fluid) contents from the compression force, so I suppose different manufacturers had different solutions to comply with the Federal safety mandates, and at least this one used the fluid filled solution...I suppose with an air volume also in the fluid reservoir, there would be some controlled and limited amount of compression (with rebound) up to the mandated limit, but beyond that, it would expel its filling, and need to be replaced with the other post-accident repairs....  .   

Marty;  If your mount "self-extended" after being compressed, that certainly suggests there is something in the way of a mechanical or even fluid [or gas] spring in there...if you determine the mechanism, I'd be very interested in knowing what it is...manufacturer Fichtel-Sachs is known for Clutches, but I believe also for Shock-Absorbers, so that might be a hint towards the oil-filled version...if you come up with further info, I will add it to the notes linked below.

I don't like the "underbite look" of the extendo-Federalo-bumpers very much, and I'm not the only one!  See:  https://www.sw-em.com/Bumper_Underbite_1800.htm "

 

[It has not yet been verified that the 1800 used such a filled energy absorber, but it is likely, given the owner noting they were "retractable and self extending", when he tested his, plus the manufacturer's info, and the fact that this manufacturer was issued a US Patent for precisely such a component.]

 

Picture by Marty of the 1800list forum, permission requested.

 

Page 1 of Patent.  Thanks to Dave Farrington for researching and finding this document.


 

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PLACEHOLDER FOR PIX OF MODIFIED [DRAINED, COMPRESSED AND WELDED TO THE SAME EXTENSION LENGTH AS NON-ENERGY ABSORBING] BUMPER MOUNTS:  "DOT UNDERBITE ELIMINATORS!"

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...Some Examples of Overbite:  

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External material sources are attributed.  Otherwise, this article is Copyright © 2023.  Ronald Kwas.   The terms Volvo and Fichtel $ Sachs are used for reference only.  I have no affiliation with either company other than to keep their products working for me, help other enthusiasts do the same, and also present my highly opinionated results of the use of their products here.  The information presented comes from my own experience and carefully considered opinion, and can be used (or not!), or ridiculed and laughed at, or worshipped, at the readers discretion.  As with any recipe, your results may vary, and you are, and will always be, in charge of your own knuckles, and future! 

You are welcome to use the information here in good health, and for your own non-commercial purposes, but if you reprint or otherwise republish this article, you must give credit to the author or link back to the SwEm site as the source.  If you don’t, you’re just a lazy, scum sucking plagiarist, and the Boston Globe wants you!  As always, if you can supply corrections, or additional objective information or experience, I will always consider it, and consider working it into the next revision of this article...along with likely the unique metaphor and probably (likely) wise-a** comment. 

 

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