Seat belts

Paul D · #1 8th April 2012, 07:20

Having hunted around for pictures and information on how other people have dealt with the issue of seat belts and mountings all over the forum, I thought it could do with a thread of it's own to be easier to find. So to kick off...

We decided to go with a four strap seat belt set for sale on Ebay. http://www.ebay.co.uk/itm/2609014157...84.m1439.l2649. £52.39 including postage for a pair seemed pretty good value. We chose a static arrangement rather than inertia reel for simplicity in mounting. (Keep it simple stupid!)

Looking around for metal in our scrap pile to fabricate some simple brackets we noticed the discarded leaves of the rear transverse leaf spring. The big attraction was that they already have a large hole in them.

The seat belt set comes with new special shoulder bolts and collet's to allow the metal ends of the belt to turn when done up tight. I found out the hard way that even now these threads are apparently all 7/16" UNF, not metric, My local bolt shop tells me that this is for all European cars - even new ones. (Please correct me on this if this is wrong).

Anyway the new bolts fit into the inner fixings welded to the centre chassis rails, so we added an outer bracket welded low down on Gary's frame, and two high level ones either side of the hump position.

We have chosen to weld captive nuts onto the mounts because they will be very difficult (if not impossible) to access with the body bonded onto the frame. The idea is to cut two slots in the back wooden panel behind each seat of the metal belt fitting to slide into and be bolted up.

The top brackets have the nuts welded on top so the bolts can be fitted from underneath with some 'studlock' to ensure they stay done up.

Pictures to follow.

Paul D · #2 8th April 2012, 07:41

Not the only or the best way to do it I am sure, but this may at least help somebody else to decide which route to take with their own build.

Charman.tech · #3 8th April 2012, 07:53

PaulD

Your post is very timely and has just sorted a problem for us in our build. we were planning to use a 3 point full harness set up, like you on the spyder going through slots on the rear ply bulkhead, by the way you can get chrome escutcheon plates from Europa spares, various shapes and sizes that will frame these slots very nicely. but our fixing will go onto the high chassis that is behind where the original rear seats were, problem is that I need to get to that area to drill a central hole to take the rear strap.

However you have solved the problem there are in fact a pair of chassis holes behind where the each of the rear seats were meaning a 4 point works beautifully where a 3 point would mean extra work.

The front points fix to the original front seat fixing points which we set a long way behind the scimitars front seats.

I know that the bolt thread is very fine on these seat belt mounting points and common to every car I have fiddle with in the past and when I did the SVA on a cobra I built some years a go they inspected those bolts to ensure they were to the correct spec.

That e-bay price looks great We will be checking those out, again thanksand this goes to shows the forum in action.

Paul D · #4 8th April 2012, 13:02

Glad to share any info, I have received so much benefit from other peoples posts.

I should have added that the seat belt kit comes with special bolts of 10,9 grade hardness. Harder than normal 8.8 grade hardened bolts.

Could be important for insurance if you later had an accident? I don't think you can just chuck in any old bolts lying around.

Socket head cap bolts can be bought in this grade of hardness, but then you need hardened washers and spacer collet's to do the job.

Paul D.

seanick · #5 8th April 2012, 21:52

Hi Paul, caution should be exercised when welding high carbon/spring steel, as it does not weld easily. I made a rudder fitting out of a shapely spring once. Arc welded with big rods, lots of amps (like 140) and good prep. When finished it just fell apart when I dropped it.
You might want to google ' welding spring steel', as they are seatbelt mounts :-(.
Nick.

davecymru · #6 9th April 2012, 10:52

I like your solution!

When i was looking into this part of my build i was reading some of the lo-cost forums and how they had to do things for the IVA and i came across the 7/16 threaded, 1" long weld-in tube adaptors that a lot of them have used:

http://www.ebay.co.uk/itm/7-16-UNF-R...-/380129249524

I've used some of them on mine due to reusing the MR2 seatbelts i had laying around and i can heartily recommend them.

tlrtone · #7 9th April 2012, 11:15

thanks Dave, I may use a couple of them for mine!

Paul D · #8 9th April 2012, 12:19

Quote:

Originally Posted by seanick

Hi Paul, caution should be exercised when welding high carbon/spring steel, as it does not weld easily. I made a rudder fitting out of a shapely spring once. Arc welded with big rods, lots of amps (like 140) and good prep. When finished it just fell apart when I dropped it.
You might want to google ' welding spring steel', as they are seatbelt mounts :-(.
Nick.

I have read the google references and agree with what you say Nick, there is definitely a concern over welding spring steel - mostly when people are trying to repair it for re-use as a spring function . Clearly the heat of welding will destroy the spring properties, which is not an issue for us.

If anybody else is concerned I would strongly suggest using a section of ordinary steel flat bar and drill it, or one of Dave's excellent threaded tubes. They look just the business and easy to position. If only I had seen them first !

Still we are where we are on our build, and the discarded leaf spring sections we used did melt into a weld pool when using the mig welder with 'gasless' wire on maximum setting. The sections are very heavily welded in on all sides and have resisted being hit with a large 'engineers spanner'.

I guess the quality of the steel in these forty year old leaf springs is not the best anyway, nothing like trying to weld a modern coilover.

Good to see other people putting their five eggs in so we can share the experience around.

cbjroms · #9 10th April 2012, 10:43

A big thank you to Paul D for starting this thread - it is something that I was just starting to think about for my build. Your ideas are great and the pictures have given me a great deal of 'food for thought'.

Davecymru - can you just clarify how you have used the weld in tube adaptors?
Have you fixed them to the frame and screwed your belts into them? Grateful for a couple of pictures if possible.

Thanks

Chris

davecymru · #10 10th April 2012, 14:43

As i mentioned, i tried to adhere to the IVA specs even thought i strictly didn't have to, as I'd never built a car before and i was quite enjoying learning news things and new skills. Or in the words of my wife, "playing about!"

As i've gone for retractable belts my setup is a bit different to Pauls, but you could easily chop-n-choose bits of both depending on how you want to do things. i.e. the top plates that Paul has done, i could have used also if i'd thought of doing it that way at the time!

I used the existing seat belt mount point on the chassis for the bottom of my belts (shown hanging loose in the below photo) and then welded a threaded tube onto each side of the body frame to mount the release stalk on to.
The release stalks are shown bolted in place in the below pic using the original seat belt bolts from the MR2 donor.

Those were seam welded in place all along both sides and are very strong and i believe have passed IVA on some 7 replicas. Although others have added an extra plate over the top in a similar vein to Pauls corner pieces for extra peace of mind if they are doing more racing.

I then welded the top mounts onto the top of the frame (again, seam welded all around) for the belt guides to bolt in to and then two more threaded tubes were welded onto an additional sub-frame i added between the cockpit and the fuel tank to hold the bottom of the retractor mechanisms with some brackets i made up.

On the below photo you can also see that the space between the Sammio frame and my additional seat belt frame has a plate welded across it for the handbrake bracket to bolt to.

And yes... I did get a bit carried away playing with my welder!

cbjroms · #11 10th April 2012, 16:54

Thanks for the photos and descriptions Davecymru,

So you weld the threaded tubes to the chassis or Sammio frame instead of using a plate and captive nut - neat idea.

Your welding looks good - are you self taught or is it part of your 'day job'?

Thanks

Chris

lancelot link · #12 14th April 2012, 12:14

We can supply these plates as welded to Andyp's frame for £4.00 each plus postage , if they help anyone ....they are tig welded.

cbjroms · #13 23rd June 2012, 15:36

I have bought the 4 strap seatbelts mentioned by PaulD. Going to get some of Davecymru's threaded inserts and drill/weld them into the appropriate places on the Sammio frame.

I am grateful for PaulD's photos and just wonder where you have fitted the 2 lower/inboard mounts? Did you fix to the Sammio tunnel frame or to existing setbelt mounting point?

Also, think that I have read somewhere that the upper mounts for a 4 point harness should be below shoulder level to provide protection in the event of a rollover! This would suggest that the top mounts need to be lower than the top of the frame?

Thanks

Chris

MoriniMan · #14 23rd June 2012, 19:14

Shoulder straps should run an a minimum angle of 10 degrees and a MAXIMUM angle of 45 degrees from horizontal. Too steep and angle and you risk a compression injury to your spine in an impact. I had to argue that one with the tech crew on Scrapheap Challenge. They insisted on full harnesses for 'safety' and then wanted to use an unsafe installation.

Lap straps should locate across the hips, not the belly. You pelvis can take the load, your guts can't.

I've run full harnesses on the road. A lot of the time they're a real inconvenience because if worn correctly they prevent you from looking over your shoulder. In the event of a roll over there's little possibility of being able to dive down into the cockpit, so I'd only run them with a rollbar.

I ran aircraft harnesses in one car which had inertia reels on the shoulder straps. They worked very well, but weren't approved for road use and had to be modified with additional buckles to allow them to be locked for spirited driving.

Ordinary spring steel is one thing, but leaf springs sometimes contain Antimony. Not only is this a toxic metal (like leaded 'free machining' steel it shouldn't be welded), but it leads to a condition known as 'hot shortness' (like short pastry) meaning it goes crumbly at high temperatures, so you could end up with it full of cracks.

Nike55 · #15 23rd June 2012, 23:22

I'm at the stage of deciding harness set up and believed the style of vehicle being built would suit a full harness, although plainly for everyday use inertia belts would be more practical, especially for passenger / navigator.

Your comments have now convinced me that common sense should not take second place to vanity and if a harness is not required then why risk the downside.

Mister Towed · #16 24th June 2012, 08:06

In a Lotus Seven replica you're pretty exposed and virtually sitting on the car rather than in it. I'd want a full harness to give me the feeling that I wouldn't fall out when going round corners.

In the Sammio though, you're pretty enclosed inside the car and it feels a very secure place to be, so a basic three point belt feels fine.

To my mind, if you're planning to race your Sammio then fit a full harness. If you're aiming for the most accurate fifties race car look possible then use a pre '67 donor and don't fit seat belts at all. If you're aiming to use it as a fun road car then go with discrete inertia belts.

Oh, and a couple of points of interest: 1/ I've fitted my inertia belts centrally as I found that to be the easiest place to get them to actually fit, although I'd probably move them about six inches further outboard if I was doing it again so they'd come out directly behind your shoulder instead of to the side; and 2/ You can't legally fit lap belts to outboard 'front' seats in any vehicle. Even if it's a pre '67 donor and doesn't need belts, if you fit any at all they must be three point belts at least.

Good luck finding a suitable solution.

Nike55 · #17 24th June 2012, 15:55

Thanks Mister Towed.

As there were no Scimitar SE5's made prior to '67 belts will be needed and it will depend how 'enclosed' the G46 body is, my seating position and how vulnerable I feel.

I don't suppose a harness will need to be quite as tight as worn in an aerobatic aeroplane, which will allow a certain freedom of movement and a friend with a Caterham advises no problem with the harness set up he has.

Will wait until I sit in it and get a 'feel' for things...

cbjroms · #18 26th June 2012, 12:28

Thanks Mr T,

Just looking around for a pair of inertia reel belts and the choice is massive.

Just wondering whether anyone knows which are the best ones to go for as regards fitting?

Thinking that I could buy a new set of Securon belts which fit the Herald and find that they are not best suited to the Sammio frame.

Clearly MR2 belts work but can anyone pinpoint other suitable donors?

Thanks

Chris

Psycho pops · #19 26th June 2012, 14:27

I have managed to fit these,

The inertia fits behind the fuel tank and the single strap glides nicely to allow the shoulder straps to slide freely over the frame behind the seats.
Nothing fixed in securely yet so no photos.
Full details in my build thread , looks of a full harness freedom of the inertia reel.
Pops

Mister Towed · #20 26th June 2012, 19:14

That inertia four point set up looks pretty good. Is that a securon multi way adjustable reel?

That's what I've used and I'd recommend them because you can have a play about with the location and always adjust them to work at any angle.

I'd also think twice about using belts from a scrap yard. Chances are they'd have been involved in a shunt and may not work as advertised a second time. New ones are reasonably cheap - I got mine off ebay for about sixty quid the pair - and one day you might really need them.