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Old 09-16-2015, 12:44 PM   #1
Joeyv
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Default 31 Roadster - Seatbelt installation

I'm getting ready to install seatbelts in my 1931 roadster. I know there has been lots of posts on ford barn regarding seatbelts, including the pros and cons and installation in various models. I decided to install them in my roadster. I haven't found a post specifically about the 1931 roadster. Before I have a go at it with 2X2 1/4 inch angle iron, I thought I'd check with you all to see if anybody has installed seatbelts in a 31 roadster and can make some recommendations. The gold ring would be if someone actually has pictures to share of a 31 roadster installation. Thank you all for your patience in reading yet another post with a seatbelt title heading!
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Old 09-16-2015, 01:48 PM   #2
J Witt
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Default Re: 31 Roadster - Seatbelt installation

Joey, Here are some pictures of mine. No added angle iron, but mounted to a panel that has built in stiffeners. This is the panel at the back of the seat box. Hope these pix are clear enough.

John
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Old 09-16-2015, 04:06 PM   #3
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Default Re: 31 Roadster - Seatbelt installation

Joey & John, I am ready to install seat belts to. It would appear that we would need more than a couple washers to hold us in. I would recommend adding a piece of flat steel stock and drill the four holes through that. What do you think? I know that seat belts in a model A are not the answer to a head-on or broadside hit from a modern day car travelling at speed, but they would be better than nothing.
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Old 09-16-2015, 07:08 PM   #4
J Witt
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Default Re: 31 Roadster - Seatbelt installation

IMHO, the problem isn't the distortion of the metal locally around the bolts, but whether or not you start a tear in the body metal. The large washers (about 5 sq in in area), which are about twice the body metal thickness are supposed to aid in not allowing the bolts to pull out by tearing the sheet metal. The washers are intended to bend along with the body metal.

If you add another stiffener, I wouldn't go any thicker than 1/8 inch steel to allow some distortion to occur, and also bevel the edges and round the corners that face against the body metal to prevent localized tearing.

Keep in mind that the belt mount points will deform the sheet metal when loaded by high stress. This is OK, but it's very important not to allow the belt mounts to tear through the body metal, thus the need for radiused edges and rounded corners. Several of the references I looked at cited a maximum of 1/8 inch thickness for the reinforcement plates.

Simpson recommends using a design load of 2500 lbs for each anchor point, but they are talking about race cars and 6 point harness. The referenced impact force for airbag/seat belt combinations for DOT is (IIRC) is 35G, but this at the impact point and is somewhat reduced by the structure crumpling. This means the force on the mounting points for a lap belt, with a 180 lb body is 6300 lbs, or 3150 per mount point. Think of being able to pick up the car by the seat belt. Keep in mind, the car isn't usable anymore after this impact.

I may be rationalizing some here, but the Model A is not a survivable container for 35G impacts, but a decently mounted seat belt will help you a lot by keeping you in the car until the action stops. This is especially true because of the poor door latches the A has.

If you really want to help the collision safety, get rid of the windshield finger pulls and the wiper motor.

All of the above is my opinion and you must make your own choices.

John
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Old 09-17-2015, 12:25 AM   #5
Joeyv
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Default Re: 31 Roadster - Seatbelt installation

Thanks for the feedback. My initial plan is to bolt a piece of 2x2 1/4" angle iron to the frame under the floor and bolt the seat belts through the floor and the angle iron. I'm not sure where to position th angle iron, or if my plan is totally flawed. I thought maybe someone tried this already and might give some tips or cautions. Thanks!
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Old 09-17-2015, 12:37 AM   #6
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Default Re: 31 Roadster - Seatbelt installation

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theres a detailed article how to install them in the MAFC book
"how to restore your model A volume 6
you can buy it from MAFCA or any Model A vendor
tom
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Old 09-17-2015, 05:15 AM   #7
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Default Re: 31 Roadster - Seatbelt installation

Don't bolt the seat belts to any frame component. If there is any body shift from the frame and your bolted to the frame....not good. Your belts should be mounted to the body sheet metal
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Old 09-17-2015, 07:36 AM   #8
Chris in CT
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Default Re: 31 Roadster - Seatbelt installation

Hi Joey,

I recently installed seat belts in my '29 roadster. I know, a 29 is not a 31, but I think you could do the same for your 31. I used a long 1 1/2 x 2 1/4 inch piece of hickory which was fitted into the body channel that holds the midway body blocks. The blocks were discarded, and the hickory stick was inserted in their place, with the ends of the hickory stick shaped like the body blocks.
1/2 inch carriage bolts were inserted through the hickory and sheet metal to anchor the seat belts, then the belts were threaded through slots cut into the seat back riser/toe space bump behind the front seat bottom. Worked like a dream and no nasty jury-rigged angle-bar to deal with. By the way, because of the strength and flexibility issues of the wood used, you must use hickory and not maple, oak or any other type of wood for this application. Sorry, but I have not learned how to post pictures, yet.
Happy Motoring!
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Old 09-17-2015, 06:25 PM   #9
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Default Re: 31 Roadster - Seatbelt installation

Quote:
Originally Posted by Chris in CT View Post
Hi Joey,

I recently installed seat belts in my '29 roadster. I know, a 29 is not a 31, but I think you could do the same for your 31. I used a long 1 1/2 x 2 1/4 inch piece of hickory which was fitted into the body channel that holds the midway body blocks. The blocks were discarded, and the hickory stick was inserted in their place, with the ends of the hickory stick shaped like the body blocks.
1/2 inch carriage bolts were inserted through the hickory and sheet metal to anchor the seat belts, then the belts were threaded through slots cut into the seat back riser/toe space bump behind the front seat bottom. Worked like a dream and no nasty jury-rigged angle-bar to deal with. By the way, because of the strength and flexibility issues of the wood used, you must use hickory and not maple, oak or any other type of wood for this application. Sorry, but I have not learned how to post pictures, yet.
Happy Motoring!
The regulations here say quite clearly that seat belts must not be attached to wood. I would be much happier with a steel member across the car rather than wood to attach to.
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Old 09-17-2015, 08:38 PM   #10
J Witt
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Default Re: 31 Roadster - Seatbelt installation

Another, smaller, caveat is that carriage bolts are generally of low grade steel and not suitable for safety installation purposes like seat belts. Most organizations that regulate such things like to see minimum SAE Grade 5 hardware.

Most of these regulations for commercial vehicles and aircraft have been paid for by sometimes bitter experience. While there are no regulations as such that I know of for our hobby cars, one should use the real world experience of others as good advice.

John
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Old 09-17-2015, 10:38 PM   #11
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Default Re: 31 Roadster - Seatbelt installation

Joey,
I posted a thread on 3/22/14 titled "Put 3 point retractable seat belts in roadster" explaining how to install belts in a "31 roadster. While everyone has different opinions on the subject, I would encourage you to review that thread and go one step further and install the combination shoulder/lap retractables in your car instead of laps belts only. Mine work perfectly and will prevent me and my passenger from eating the steering wheel or smashing our heads through the windshield. an event laps will not prevent. Of course, a serious hit by a semi to a model A likely will not protect us in any event no matter how well we design our belts. The thread also has photos of the installation.

PM me if I can be any help with your installation.

Glen
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Old 09-18-2015, 04:37 PM   #12
Joeyv
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Default Re: 31 Roadster - Seatbelt installation

Thank you all for you suggestions and feedback. I installed lap belts yesterday, in preparation for International Model A day tomorrow. I wanted to get something in before I take the car out for our first tour (ever). I may go back and upgrade the installation (e.g. 3 point belts), based on some of your suggestions. I currently have the outer belts anchored to the bolt that holding the body to the chassis. The inner belts are attached through the floor pan and they are backed by a 6 x 13 x 1/4 piece of steel. That should hold my body in the car for low speed mishaps, although I may still may collide with the steering column. Thanks again for sharing your wisdom!
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