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Author: Subject: DIY Ladder Chassis
jimthesail

posted on 14/2/21 at 01:53 PM Reply With Quote
DIY Ladder Chassis

Ahoy ! I am interested in building from scratch a ladder chassis for a 'vintage' style kit car.
(There appear to be no current producers of such chassis.)
My take on this is that the DVLC require 'Type Approval' which is gained by passing the IVA.
However the IVA guide goes into great detail on the strength requirements of the seat belt anchorages,
quoting Directive 76/115/EEC and requiring either 'evidence' or visual assessment but only
requires an 'assessment' of the structure by the examiner under General Construction.
What problems am I likely to encounter by building what is basically a special ?





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CosKev3

posted on 14/2/21 at 04:19 PM Reply With Quote
As long as you copy the seatbelt mountings of a seven type car you will be fine.
Just basically a threaded boss welded to the chassis with some triangulation

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jimthesail

posted on 14/2/21 at 05:10 PM Reply With Quote
Ladder Chassis

Thanks for that.
I have used 50 x 50 x 6mm tags welded along both sides of one edge onto the 80 x 40 box chassis on a current build.
Threaded for the 7/16 UNF bolts and lock nutted.
Acceptable ?





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CorseChris

posted on 16/2/21 at 02:28 PM Reply With Quote
I'd weld a nut to the outside of the plate rather than relying on threading it, as it's only 6mm thick. They don't like supports in single shear either, so beware making those plates too big a distance from chassis tube to belt mounting hole. Take plenty of pictures too and send them off with the application as well as take them with you to the test - if the examiner wants to see something its much less hassle if you can show a picture than having to potentially strip stuff down.

Following my own recent IVA experience, I would say be ready for increased scrutiny on a home-brew chassis as opposed to a 'professionally made' one. My examiner told me that whenever he sees a DVLASWA prefixed chassis number on the paperwork he prepares himself for the worst. He did look very closely at what I had presented but was quickly convinced it was a decent design and I had done a decent job of fabricating it. In fact, he was most complimentary, which was nice.

[Edited on 16/2/21 by CorseChris]

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jimthesail

posted on 16/2/21 at 04:13 PM Reply With Quote
Ladder Chassis

Thanks for that. By my calculations a 50 x 6mm tag properly welded should have a yield point of 16 tons so three of these should keep one in place !
See what you mean regarding length; they would become very suspect if long and whippy. I am beginning to get the picture that the reason for the decline of the older ladder chassis/plywood bodied kit car is due to lack of identifiable strength in components such as seat mounts/brake pedal boxes/steering column support etc ?





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CorseChris

posted on 16/2/21 at 04:32 PM Reply With Quote
quote:
Originally posted by jimthesail
Thanks for that. By my calculations a 50 x 6mm tag properly welded should have a yield point of 16 tons so three of these should keep one in place !
See what you mean regarding length; they would become very suspect if long and whippy. I am beginning to get the picture that the reason for the decline of the older ladder chassis/plywood bodied kit car is due to lack of identifiable strength in components such as seat mounts/brake pedal boxes/steering column support etc ?


They are a lot more picky than they used to be!

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