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High or Low frame

This is a question that is probably obvious but what is the difference between a high and a low frame, is the top hat section deeper?

Cheers

Mark

Location: Rokeby, Victoria, Australia

Re: High or Low frame

As far as I know it's the setting of the road springs, the low frame sitting nearer the road.

Location: Just north of Cambridge

Re: High or Low frame

Chassis rails are similar RP but front bracket has greater step down, and rear springs set with less camber.
The most immediate identifier is the chassis extensions which are serious channel sections instead of the light angle pieces of the earlier cars, for which on some models it is questionable if the extensions support the body or vice versa.

Location: Auckland, NZ

Re: High or Low frame

Thank You Bob, a greater step in the front bracket makes sense.

Cheers

Mark

Location: Rokeby, Victoria, Australia

Re: High or Low frame

The only parts that are interchangeable between a 1934 or earlier RP high chassis frame and a 1934 or later Ruby low frame are BR6 and BR7, front crossmember brackets, BM123 radius arm ball, BR48 floor support ( x 2 on RP, but only 1 on Ruby ) and a handful of rivets.

Re: High or Low frame

if you buy a parts book for the austin 7.

the ones for the ruby models late 1934 to 1938. usually have on the front cover. low frame models.

so yes the springs are set lower 3 1/4 inch camber.

all chassis 1934 box saloon and earlier are high frame. 5.5 inch or vintage cars 6.5 inch.

the veriation between the two chassis.

is mainly the rear extensions. and the nose casting.

tony

Location: huncote on the pig

Re: High or Low frame

Bob Culver
Chassis rails are similar RP but front bracket has greater step down, and rear springs set with less camber.
The most immediate identifier is the chassis extensions which are serious channel sections instead of the light angle pieces of the earlier cars, for which on some models it is questionable if the extensions support the body or vice versa.


There is no difference whatsoever in the front bracket step down, both Vintage high frame and Ruby low frame are 2" the angle of the underside is slightly different and the cowhorn mounting holes move but that is it. The rails of a Ruby chassis have a deeper return flange on the inside edge where the extensions attach, but the section of the main box of the rail is the same on the LWB chassis.

Location: NZ

Re: High or Low frame

Ian, if that is the case then there is really no such thing as a High or Low frame as if you are right then it's just the spring camber that gives a different height.

Location: Rokeby, Victoria, Australia

Re: High or Low frame

Ian Williams
Bob Culver
Chassis rails are similar RP but front bracket has greater step down, and rear springs set with less camber.
The most immediate identifier is the chassis extensions which are serious channel sections instead of the light angle pieces of the earlier cars, for which on some models it is questionable if the extensions support the body or vice versa.


There is no difference whatsoever in the front bracket step down, both Vintage high frame and Ruby low frame are 2" the angle of the underside is slightly different and the cowhorn mounting holes move but that is it. The rails of a Ruby chassis have a deeper return flange on the inside edge where the extensions attach, but the section of the main box of the rail is the same on the LWB chassis.


Surely,if the rear only is raised there would be a change in caster angle as the king pins would be more vertical.

Location: Piddle Valley

Re: High or Low frame

Yes that is why there is an angle change as I stated Peter.

Location: NZ

Re: High or Low frame

So there is a change to the steering geometry upon the introduction of the high frame,or are the king pin angles changed in the front axle to compensate and allow original caster to be kept?

Location: Piddle Valley

Re: High or Low frame

Peter,
Also don't forget, the difference in hight between 19 x 3.50 tyres and 17 x 4.00 tyres bringing the caster back 1 inch

Tony.

Location: Huncote on the pig

Re: High or Low frame

Tony betts
Peter,
Also don't forget, the difference in hight between 19 x 3.50 tyres and 17 x 4.00 tyres bringing the caster back 1 inch

Tony.

Location: Piddle Valley

Re: High or Low frame

I've never noticed if there is a difference in camber in the nose piece.

There are different heights of front springs, that would even things out. After wheel sizes.

I mension the nose piece as different, as IAN says the cow horn holes are in different positions.

I look at the nose as being 2 different items.because of the ebay users, there is usually a difference in valued price. Early ones always being more expensive, for those wanting to built a vintage chassis. Ulster etc.

But on ebay many will fall for paying to much for the latter Ruby type, thinking they have the same thing as an earlier nose.

There are other small difference for fitting gearbox, body etc. But thought just the main differences would sort this question.

Tony.

Location: Huncote on the pig

Re: High or Low frame

Thanks Ian.

Of all my alleged many errors the first anyone has troubled to explain.
I compared the brackets years ago and noticed a difference but obviously not in the stepdown.
A consolation, unlike many of the errors in books and Club publications, unlikely to have inconvenienced anyone.

Location: Auckland, NZ

Re: High or Low frame

The measured difference between the two types is just over 1 degree, I have just double checked two vintage 1926 and 1929 chassis, against two post vintage 1936 and 1938 chassis, the variance is reasonably consistent when measured with an engineers protractor.


And Bob my issue with you is that you make statements such as there is a difference in set dow when you don't actually know. It is extremely misleading to the less well informed, why not simply say that you wonder if the set down was altered and ask the question. That way you would not mislead others or **** off those of us who do know what we are talking about, by now most simply can not be bothered with you any more.

Location: NZ

Re: High or Low frame

So as a summary the term "low frame" has nothing to do with the section of the frame. It is instead that the chassis sits lower, this is achieved by less camber in the rear springs with a small change to the front nose piece to compensate for the caster change that the rear lowering would cause.

So apart from the nose piece the frames are practically the same.

It is a pity that Bob's explanation was not correct as it seemed to have more going for it.

Cheers

Mark
from wet and cold Aus

Location: Rokeby, Victoria, Australia

Re: High or Low frame

The front crossmember is certainly diferent. The low frame version has a dip in the middle where the ball is for the radius rods to the axle. No doubt to cater for the different 'angle of dangle' of the front axle as noted by ians measurement of the nose piece.

Location: not north wales any more

Re: High or Low frame

There are lot's of subtle and a few not so subtle differences, as Henry said above very little is identical to what came before.

Location: NZ

Re: High or Low frame

From the A7CA Archive, Spare Parts List 1218A shows both high and low frame chassis in detail on pages 55, 56,57 and 58.

As with most Spares lists there are a few oddities but in general this shows the differences (it doesn't note the different nosepiece angles)

The cards may give more information.

http://archive.a7ca.org/wp-content/uploads/PL_1218A.pdf

Cheers, Tony.

Location: Melbourne, Victoria, Australia.

Re: High or Low frame

So under the heading Low Frame you have Front Spring Bracket BR155, under heading Low and High Frame you have Front Spring Bracket BR47 with no Front Spring Bracket list individually for the low frame. I suppose this could be a typo?

The plot thickens.



Location: Rokeby, Victoria, Australia

Re: High or Low frame

Hi Mark,

"As with most Spares lists there are a few oddities"

From earlier Spares Lists for the then standard chassis which later became designated the 'high frame', BR 47 is the correct original front bracket.

Cheers, Tony.

Location: Melbourne, Victoria, Australia.