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Hey Clint,

What would the rules be regarding shortening the length of a full chassis?

Ie, say a 1946 dodge truck. Quite a long truck, really needs to put cut down to mor ratrod friendly length. I'm told it'd most likely be a "C" section Chassis.

Could it just be cut down, and welded up?

Or would it have to be ground back so you couldn't tell it'd been done, and then just plead ignorance?

A distant cousin of my dads has one that's been sitting on his farm for 25 years, but it pretty rust free. The authentic outdoor weathered look just screams rat rod. But it's far too long.

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Hey cletus, what is the go with chopping frame rails shorter, but then welding beefier steel in? would that need to be certed? Or would it be ok if it looked legit enough?

depends, what are you looking at doing?

any structural modifications need cert.

The frames measure 65(w)x45(h)x1.2 wall.

If I replace them with something that's 65x25x5mm would that be ok? What sort of strength are we looking for, second moment of area?

Y is deceasing so to keep the stress constant fir a given force you have to increase I value by the same factor that you are removing rail height ie 1.8.

Edit: my bad if im telling you to suck eggs etc its just this is what I am doing atm to prove to my cert guy what in doing is legit etc.

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Hey cletus, what is the go with chopping frame rails shorter, but then welding beefier steel in? would that need to be certed? Or would it be ok if it looked legit enough?

depends, what are you looking at doing?

any structural modifications need cert.

The frames measure 65(w)x45(h)x1.2 wall.

If I replace them with something that's 65x25x5mm would that be ok? What sort of strength are we looking for, second moment of area?

what is the application? what part are you replacing? the whole chassis rail? or just a part? on an mx5?

would probably need a certifier to look at it to give you an accurate answer.

Supplying engineers calculations will be helpful ie what brockolee said

Edit: my bad if im telling you to suck eggs etc its just this is what I am doing atm to prove to my cert guy what in doing is legit etc.

not at all..... im still learning how to suck an egg properly :mrgreen:

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Hey Clint,

What would the rules be regarding shortening the length of a full chassis?

Ie, say a 1946 dodge truck. Quite a long truck, really needs to put cut down to mor ratrod friendly length. I'm told it'd most likely be a "C" section Chassis.

Could it just be cut down, and welded up?

yep thats fine, cut it on an angle, butt weld it back together, then a fish plate twice as long as the height of the rail over the join. there are other methods in the book but thats probably the easiest to explain/do

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Cheers Clint! You're the man.

Would the fish plates also need to go on the top and bottom of the [ section? Or just each side? Depending on how crisp the folds in the chassis rail section are, it could be possible to fold up an inside and an outside fishplate to completely cover the join. Or wouwld it be prefered to only have it inside and on the outside of the vertical rail section to enabale a good longitudinal weld?

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Cheers Clint! You're the man.

Would the fish plates also need to go on the top and bottom of the [ section? Or just each side? Depending on how crisp the folds in the chassis rail section are, it could be possible to fold up an inside and an outside fishplate to completely cover the join. Or wouwld it be prefered to only have it inside and on the outside of the vertical rail section to enabale a good longitudinal weld?

what you are describing would be fine. its only required on one side of the rail.

an alternative is to cap the top and bottom part of the [ instead of the vertical part

personally i think it looks neater to do just the inside of the [ (or what you described, completely cover the inside join)

when i did the chassis join on a previous project it was a box section, cut it in half, cut 100mm extra from the inner wall each side of the join, fish plate on the inside of the rail, then folded up 200mm long [ section for the inner wall and tig it all together, was hard to see where it was joined

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Is the form you need to fill out regarding the modifications to the car before cert available online? I can't seem to find it on the LVVTA website.

ive never seen a form like that?

maybe a certifier made one up and gave it to you?

its a good idea actually, would make life easier identifying whats been changed on a car

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if you could see what number is on it or even a pic would be handy. Might be something thats prior to me starting certing that i dont know about.

It may be the 2nd page in the formset, that lists all the mods on the car, usually is filled out by the certifier.

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from LVVTA website-

Do I need LVV Certification if I have a Modification Declaration Certificate?

Cars that were modified prior to 1 January 1992 were issued with a Modification Declaration Certificate at that time. The Modification Declaration Certificate is valid as long as the vehicle is continually registered and until changes are made to the vehicle, at which time the vehicle must be LVV certified and issued with an LVV plate. Provided the vehicle is still the same as it was in 1992, the Modification Declaration Certificate continues to be valid today for WOF purposes. The WOF issuer is able to check with LVVTA or NZTA to verify details on the certificate.

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