Rear shoulder belt anchor point

[californiabristol]

I am trying to reposition the shoulder belt anchor point on the rear belts of my 411. Currently, the re-tractors are located above the fuel tank directly
behind the rear seat positions( i.e. on the parcel shelf). I want to move
the re-tractors outboard so the belt does not fall directly on the neck.

Can anyone tell me if the rear wheel well is a better location to mount the re-tractor? This would be a simple solution provided the wheel well is not
rusted!

Greg Woog

[irienz]

The upper end of the front seatbelts in my 411 are mounted at the top of the rear inner guards. Several years ago the mountings were discovered to be badly corroded and the restorer reported that he had been able to pull belt mount out of the guard easily by hand so watchfulness of structural integrity is certainly essential!

I fitted lap belts only in the rear of the 411 because of the lack of a proper upper mount, the inner rear guard already bearing the front upper mount. I obtained an engineer's report that the 411 lacked anything sufficiently structural for a mounting in order to obtain an exemption from the usual three-point belt requirement in New Zealand when it was imported here. I would not have thought that the rear parcel shelf was an adequate mounting surface.

Chris Browne

[californiabristol]

Chris,

Thank you for your reply. I purchased my car in England, and as it had
a current MOT, I assumed that the seat belt mountings met some
sort of regulation. The front shoulder belt upper guides in my 411
are mounted to the top of the B-post( re-tractors fixed to the B post base).
The rear shoulder belt retractors are mounted on bars spanning the sheet
metal below the rear screen and the bulkhead in front of the fuel tank.
It sounds like moving the retractors to reinforced locations atop the
rear wheel wells should be safer.

Greg Woog

[Kevin H]

Greg,

That doesn't look very secure.

This is how they are mounted on my 411, which I believe is original.

I will see if I can find some better photos.

Regards,
Kevin

[lansdownplace]

Greg, I would be very careful with this. There is no existing structure for the top anchor on the 411 capable of supporting the forces experienced in a full on crash. Rear belts weren't required or even dreamt of back then Bristol only provided a structure for them when it built the 603 series cars. You have to weld in a support from the chassis. Bristol themselves won't fit three points in the rear unless they are putting in the extra superstructure as they have liability if it goes wrong.

Many cars have the anchors fixed to the parcel shelf alone, which is OK provided you accept that a big shunt with an adult in the back risks failure big time. Whilst Bristol won't put one in, there are lots of owners and back-streeters who will so there is a risk that the rear belts on any 411 are dangerous. For any 411 owners out there who aren't sure of the provenance of your rear belts, I would check them out. They are the kind of item that is only stress checked on first and last use.

Lap belts are safer from the point of view that they can be anchored to the chassis and are a cheaper fix, if a bit messy and not so good in a crash

Paul

[bkz411]

My 411 Series 6 which is a nut and bolt restoration of a Series 4. It has,
what I would call, 'normal' seat belts in the back. I use them daily for my
kids, who both use child seats as well.

I am not technical when it comes to cars - but if you would like I can take
a picture of them if that would help shed more light on what is possible?
Let me know if this would help.

John

[Kevin H]

Greg,

Bristol introduced inertia reel seat belts for rear seats in the 411 S5, along with rear headrests.

However, they didn't mount the seatbelt reels on the parcel shelf, as my photos show.

Regards,
Kevin

[dezelsky]

I spoke to Bristol Cars Services recently and was quoted £700 to install rear inertia belts in my 411 S4. This seems reasonable to me and am planning to proceed. I believe they weld a strengthening bar under the parcel shelf, so I am not sure that the end result will be aesthetically pleasing. It would be better to mount in tandem with front belt anchor to the wheel arch so the belt mechanism can be hidden, but presumably this would require considerable load strengthening (I have also encountered serious corrosion problems here). There may also be a space space restriction for mounting 2 inertia mechanisms.

[Kevin H]

Greg,

I have searched high and low and can't find any decent photos of the seat belt reel mountings on my 411.

Given that you are in the USA and it is not economically viable to send your car to Bristol Cars to have them fitted properly, they might be prepared to send you some drawings of what needs to be done, or perhaps they could send you some better photos.

Failing that, I can remove my rear seat and parcel shelf and take some better photos and provide a detailed description of how they are mounted in my car - I am quite sure it is an original factory fitment from when the car was made.

Regards,
Kevin

[californiabristol]

Thanks to all for your advice and help.

Kevin, it is interesting to see that the factory placement for the rear(?) shoulder belt re-tractors are mounted on the longitudinal, rectangular-sectioned member out board of the fuel tank. This looks reinforced on your car. Your pictures are already very helpful. I have included some additional photos to show the current seat belt mountings on my car.
I am certain the rears are not original, and I believe I have receipts for their fitting. BCL would be the best source for advice. It won't hurt to ask.

Does the B-post mounting for the front shoulder belt guide look suspect to anyone?

Paul , I agree that the rear mounting is probably not safe, and the easiest solution would be to revert to simple lap belts as on John's Series 6
since the mounting points are already there. John, I am certain that the lower mounting points are original, but it would be good to get some
reliable, as-new images of the original seat belts for the forum(s). Pictures of your beautiful car would be nice in any case!

Paul D. good luck with your new seat belts from BCL. Please let me know how the new belts are mounted.

Thanks again,

Greg

[bkz411]

On my way out this morning I managed to take these pictures. Sorry for the dust, but I was in a rush and I have only noticed it now. The kids seats were in the back which must have hidden it from my view during my various cleans.
Not sure if these will be of any use, but hope they are of interest. I believe the back seat belts have three points, not two.

[Claude]

I have a bit of concern about the seat belt postings.

Doing a quick google search I found Car Crash Example that suggests a 30 mph crash puts about 1.5 tons of stress on the seat belt anchor points. At 60 mph this jumps to 9 tons, and it presumes a stopping distance of 1 foot. If the car hits a concrete wall with 0.01' stopping distance, the calculator jumps to 960 tons. Obviously the crumple effect of a Bristol will mitigate these numbers in real life. But if the belt gives way while the car is coming to rest, the g-forces on the body hitting the windscreen and dashboard will be horrible.

The problem with seatbelts is they only are tested once, and if they fail the results can be life altering. I am not sure if we have statistics on seatbelt-testing crashes in Bristols. I know that the BMW C1 web site had a page for crash reports, which we filed when the chairman of my charitable trust hit a car at 40 kph and walked away uninjured because the C1 has two shoulder belts and a lap belt. I wonder if we should not have a similar web page for Bristols. Kevin?

The problem with photographs of location in the Bristols is they do not tell us the most crucial part, what is holding the belts to the car and how strong is the mounting. This is a problem for both front and rear, as old Bristols lack a B pillar. If I ever get my 411 back on the road, it needs to pass VIN on seatbelt mountings, as approved by an engineer. The challenge is to determine how to do that best.

It would be helpful if Bristol Cars provided a certified instruction set that could be followed and signed off by the New Zealand inspector. Lacking that, it would be helpful if an engineering-oriented Bristol owner could provide an engineered solution that would not carry legal liability, but provide the crucial real-life information.

From my racing days, of course, a simple roll bar does the trick, a heavy piece of bent round steel with four mountings and a total of 16 large bolts braced in the floor. It may be that for the rear of a Bristol a similar U shaped piece of steel, perhaps in box form to lower its profile is way to address the rear.

Incidentally, in my Bristol 409 (under the old NZ rules), the engineer simply charged me $500 to advertise in an official NZ registry that the car had no place to mount shoulder belts in the front. Ironically, the car came with original Bristol aeroplane seat belts (the driver's one had a parachute icon on it). But those belts were deemed to not meet the NZ standard, so rather than allow them to remain and give some protection, the regulation required they be removed, giving no protection. Even more annoying the engineer decided they were surplus, and took them as a souvenir. Recovered one, the other one was "lost".

Claude

[lansdownplace]

Hi Claude,

Thank you for this very detailed posting. The forces involved are quite incredible.

My 412 has the front seat belt upper anchor fitted to the chassis member roughly where the rear passengers elbow rests in the back seat. You have to rummage around behind the front seat for the belt which is good for mobility I suppose.

The rear upper anchors are routed through a roller on the rear parcel shelf with the anchors bolted directly to a newly inserted chassis extension. I was mildly surprised at the cost of installing them as I thought it was just a case of bolting them in. It was markedly cheaper for me as the whole car was being disassembled anyway. Lap belts were a pretty cheap option but I think they look a bit messy and they do cause injuries which is why they are banned in new cars now. I was specifically warned about the problems of bolting them to the parcel shelf and the consequences.

Unfortunately I can't take any pictures as my car is in for some tuning tweaks at the moment.

Paul

[californiabristol]

Thanks for the images. I was looking at interior photos posted on the BOC site, and the front retractor mounting on top of the rear wheel well is common. The rears on your car appear the same as Howards. I can only hope my B-post
mounting location for the fronts is ok.

Greg Woog