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modelbuilder

Help please re. Body to chassis figment.

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My friend has just lowered his body onto a rebuilt chassis and is having self doubt about his work.

To start with, he is a brilliant engineer and has been very methodical in the process of repairing the chassis. He built the most amazing jig prior to removing the rear chassis etc. The chassis and cross members are all new from the t shirt back. Having seen the jig arrangement and the way he measured everything prior to starting the removal of the original rusty sections, I cannot believe that he has misaligned anything.

The floor to chassis mounting points have only needed a couple of spacers as have to rearmost mountings.

However the cross member that goes under the spare wheel well is at least a couple of inches away from the replaced boot floor. We are wondering how good the shape of the replacement floor is.

Also the mounting point in the first photo there is at least a couple of inches gap between the body and chassis.

I would be interested in any comments from anyone who has an unrestored car or from anyone who may have experienced similar problems during a rebuild.

Thanks, Rodders.

PS the title is not a figment but fitment!

post-3527-0-90577500-1526386498_thumb.jpeg

post-3527-0-88843900-1526386511_thumb.jpeg

Edited by modelbuilder

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Judging by the angle of the rear end of the chassis to the boot floor he has managed to "Hog" the chassis.I will give you a ring and explain later.

Stuart.

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Hello Stuart,

 

I am interested to understand also the concept of an Hog Chassis and the solution.... if you explain and share on the Forum

 

Thanks' and best regards

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Speak with Stuart ,the angle of boot floor to chassis is wrong 3/8” is a better guide

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Hello Stuart,

 

I am interested to understand also the concept of an Hog Chassis and the solution.... if you explain and share on the Forum

 

Thanks' and best regards

In essence when replacing the trailing arm sections and the "T" shirt section (Usually required) and often also sections of the rear legs of the chassis its very easy for the chassis to warp upwards at the rear, some more than others thus producing what you see in the above picture. Normally the boot floor when viewed side on with the shell sat on the chassis would be pretty much parallel to the rear chassis leg just slightly closer at the tail end.The clearance at the front of the spring bridge where the parcel shelf mount is around 3/16" to sometimes 3/8" depending on the shell.Also at the rear of the car there shouldnt be that much of the rear chassis legs showing from behind 1/2" to 3/4" is usual.

Stuart.

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I agree with Stuart although I thought the term 'hogged' was used to describe the rear chassis sagging down rather than raising.

 

Anyway, I have a brand new CTM '6' chassis in my garage (assuming 5 and 6 are the same) and I've taken a measurement for you. The chassis is pretty much flat until it starts to kick up, just in front of the rear diff bridge. With a straight edge under the chassis below the spring/diff bridge, the base of the chassis kicks up by 90mm at the rearmost point.

 

Hope that makes sense!!!

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I wonder if the restorer has taken all his measurements from the original chassis which may have already been hogged. Consequently, creating a perfect reproduction of a hogged chassis.

 

Not good news whatever has happened.

 

Graeme

Edited by graeme

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Hi Chris,

in aerospace Hogging is where the centre of the fuselage is raised above the cockpit and the taiplane

Sagging is where the centre of the fuselage is below the cockpit and tailplane

 

When I got my new chassis back in the 90's from a shed in Birmingham I also found my back end was seriously too high.

I ended up cutting the chassis just forward of the diff rear support.

This caused the diff attachment points to move rearwards so the rear bridge had to be removed and re-positioned.

 

Roger

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Hello Stuart, thanks' for this education note.

Best regards

In essence when replacing the trailing arm sections and the "T" shirt section (Usually required) and often also sections of the rear legs of the chassis its very easy for the chassis to warp upwards at the rear, some more than others thus producing what you see in the above picture. Normally the boot floor when viewed side on with the shell sat on the chassis would be pretty much parallel to the rear chassis leg just slightly closer at the tail end.The clearance at the front of the spring bridge where the parcel shelf mount is around 3/16" to sometimes 3/8" depending on the shell.Also at the rear of the car there shouldnt be that much of the rear chassis legs showing from behind 1/2" to 3/4" is usual.

Stuart.

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Hello RogerH, good point to clarify Hogging vs Sagging for a French guy like me.

Best regards

Hi Chris,

in aerospace Hogging is where the centre of the fuselage is raised above the cockpit and the taiplane

Sagging is where the centre of the fuselage is below the cockpit and tailplane

 

When I got my new chassis back in the 90's from a shed in Birmingham I also found my back end was seriously too high.

I ended up cutting the chassis just forward of the diff rear support.

This caused the diff attachment points to move rearwards so the rear bridge had to be removed and re-positioned.

 

Roger

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I wonder if the restorer has taken all his measurements from the original chassis which may have already been hogged. Consequently, creating a perfect reproduction of a hogged chassis.

 

Not good news whatever has happened.

 

Graeme

When I talked to Rodney he confirmed the guy had taken all his measurements etc from the chassis when he removed it and then repaired it to them hence the problem.

Stuart.

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You can find the chassis dimensions in the brown bible.

Waldi

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My heart goes out to the builder of the chassis...that's an awful amount of time and energy invested...to no avail...I hope he can summon the energy to peserve and correct the error.

Len

Edited by len1

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Thanks for all the replies and a special thanks to Stuart who, as usual, is always there for the best advice. Rest assured, Peter will correct the problem and in due course I will report back with the outcome.

There is no substitute for experience! Weve all made, what in hindsight, is an obvious mistake.

Rodders, ( without a TR after 54 years ).

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