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MG Midget and Sprite Technical - Type 9 gearbox crossmember

I would like to know what the crossmember looks like and how it fits to the underside of the car. Also how the gearbox mount is located.
Anyone got any pictures?
Thanks

Les
Les Robinson

It looks like a 1cm thick steel plate , also has a 1cm high rib welded across it, holes drilled in the appropriate places.

The plate is square with a 3" deep notch to clear between the old crossmember

The bolts go thru the old crossmember at the front and thru the floor close to the tunnel at the rear
Will Munns

I have one in my garage Les. I will try and remember to take a pic of it tonight and provide you with some dimensions.

John
John Payne

I'd like to see the way the gearbox is mounted into the plate if anyone has a picture or two

please
Bill

Here's a home made version:
http://www.the-wizardsden.com/mg_home/gearbox.htm
he details the whole procedure for a 1500 midget.
Graham P

Just for info, I have just rebuilt my Type 9 gearbox and its now ready to fit.
To avoid all the faffing about required to adapt the clutch etc I have used a different approach.
The root diameter of the Ford input spline is slightly larger than the OD of the Spridget spline. So what Ive done is to grind off the Ford spline to make the shaft profile resemble the Spridget shaft including the spigot bush location dia. Then the correct Spridget 10 tooth spline has been spark eroded onto the Ford shaft - hey presto, a Ford shaft that thinks its a Sprite shaft.
I had a scrap smoothcase housing and have sawn off the bell housing and had it welded to an adaptor plate.
The result is a Type 9 box that will fit directly without any changes to the clutch or engine.
One concern that I had was that by grinding the Ford shaft would the material hardness would be lost by going through the case depth. I have checked the hardness and its 57 HRc at the spigot bush end and 51 HRc at the spline so no problems there - either the Ford shaft has a very deep case or its through hardened.
I'd upload some piccies but don't know how to do it!

Les
Les Robinson

My crossmember for the type 9 is a very simple affair. It uses a ford Fiesta lower engine mount rubber as a support that screws directly into the alloy gearbox tail casing.

Guy


Guy Weller

Here is the Frontline one - 6mm steel. The extra slots are so it works for K series or 1500 perhaps. Mine is 1275.

Will come back with dimensions if required.



John Payne

The picture implies using the Ford cross brace and mounting, is that the score John?

Would certainly keep the back of the box more steady which has been my only slight quibble and why I set up the engine steady brace.
Bill

Guy's type is probably the way to go, simple and light. The only thing with the plate type is I suppose it is trying to put the strength back into the shell after removing the original x member. Don't think Guy's ever reported his car falling to bits though!!

I removed the Frontline one and made an identical one out of ally - saves 1.5 kg!
John Payne

Mine extends further side to side than the frontline one - it is 26" long. I think is better as it adds rigidity across the shell, completing the "hoop" which is formed by the scuttle, A posts and cross member.
My gearbox is supported on a single point which stops it dragging along the road, but doesn't resist any side or torque movements too well. Basically the whole "lump" is supported at three points like a three legged stool. I did have one of the front engine mountings crack which might have been as a result of this. I have since added a head steady which seems to hold everything more firmly in place.

There is a slight tendency for my gearbox cross member to twist down at the back as all 4 fixings to the body tub are is a single row and the shoe that supports the mounting rubber is welded onto the back of the cross member. It probably should have a couple of extension plates pointing rearwards on either side, and 2 extra bolts through the floor. But so far it hasn't caused any serious problems.


Guy Weller

If someone could post the dimensions up of the Frontline one that would help me loads. Do we know what the rib is for?
E Brown

This is what MMC were supplying about year 2000. Two inserts to go into the existing cut crossmember and a simple "U" shaped plate that you had to align and drill when clamped in position.

Guy


Guy Weller

when you have to drill new holes through the H section cross member, does anyone have any tips for aligning the holes on either side. Also you must need a pretty long drill? My previous experiences of drilling through box section is that your hole never comes out exactly opposite your entry point and as I dont want wonky bolts....
Nick

I think Guy's idea sounds good. A long square or rectangular section running across the car, made as long and as deep as possible. To prevent twisting a plate should be welded on top that extends rearwards and bolted through the floor.
I'm not sure how much stiffness the existing crossmember gives to the whole structure, its also there to support the jacking points, which I don't use anyway. Either way, its best to make the structure as stiff as possible.
The section should be located directly beneath the existing crossmember. I plan to insert a 12mm plate with tapped holes so that the section can be bolted through. I don't think its necessary to bolt all the way through the crossmember but just the bottom/floor panel. The 12mm plate will add rigidity and spread the clamp load.
For the gearbox mount, is it possible to adapt the existing Spridget mount, this will give lateral support - will have a look at this.

Les
Les Robinson

Scroll to the bottom of the page here:

http://www.tooke.org.uk/convert.htm

Easy to do with a bit of steel plate and a drill. Been on the car for about 3 years now and as good as the day it was fitted.
Bob T

Les,

Years ago when I fitted a Ford 4 speed I made an adapter between the Ford gearbox mount point and the A series mount, it comprised a steel V to fit the Ford mount point with another V welded to the back to fit the spridget gearbox mount. I never actaully used it as in the end I used a Ford escort RWD gearbox mount, same often used for the t9 conversion, directly onto the crossmember. I later regretted it as the Ford mount always seemed much softer than the spridget gearbox mount and allowed the back end to move more than I would like. My current intention when going K or at least 5 speed is to look at cutting off the standard Ford mount point and fitting a cradle using the extension housing bolts as pick-up points, the cradle most likely fitting to the standard spridget gearbox mount.
David Billington

Les describes pretty well what I did.
The length (26") is pretty well dictated by the alignment of the exhaust pipe under the floor, unless you make it longer one side than the other.
Mine bolts through the floor into the cross member void but not right through the top of the box into the car. I use a 4mm plate that goes inside the cross member. It has a captive nut welded on the top surface for the inboard fixing points and a downwards pointing bolt welded through the plate for the outer fixing. This makes it easier to align and fit the crossmember when grovelling under the car, single handed. I didn't cap the cut crossmember so one can feed these reinforcing plates into position. They provide the reinforcing and avoid the potential problem of using long bolts which could crush the cross member if not fitted with some sort of spacer. The cut ends of the cross member are sealed with plastic bungs as found on cheapo office furniture - only larger!




Guy Weller

I like the idea of not drilling the whole way through the box section as per frontlines instructions. Would the following work ok (a mix of frontline bits and guys design)?


Nick

Similar to mine. Using a box section insert like that is probably stronger, but your diagram wouldn't work as you cannot insert the box section with a captive bolt already installed. You need to get as much spread between the bolt fixings as you can to avoid any "hinged" cross member effect.

Guy
Guy Weller

Sorry guy the plate with the captive nut and bolt is seperate to the insert! I'd hammer the insert in (with waxoyl behind) then drill the holes then put the spreader plate inside.

Also I just found this company - useful!: http://www.rosshandling.co.uk/tube-inserts-2.asp
Nick


Moss Plastic Parts do an enormous range of plastic bungs, hinges, latches, hardware, plugs and protectors and stuff.

And they'll send you a couple of samples for free.

www.mossplastics.com
MarkH

Yes Nick that's where I got them from. They supplied mine as free samples as Mark says.

Sorry - I misread your diagram!
Guy Weller

My "Guy-type" fitting is drilled through top and bottom of the cross member which has been plugged as James Mather did it with 20mm tube sctions squared up and welded together.

This gives the box section enough rigidity to take the pressure of the bolt being tightened between both sides of the crossmember box. Stops any distortion happening

Then I welded a plate across the inner ends where the gap was cut out so no rust is encouraged inside it.

I used my angle grinder to cut out the crossmember

huge, colossal mistake!

I should have taken a more controlled approach and used a simple hacksaw, I had to re-tidy it all up befor fixing all the stupid holes in the wrong places and the saw was actually easier to cut with inside and underneath as I was.

this picture shows the damage I made which subsequently needed repairing, thank the Lord for Mr MIG...

But it shows too the nine 20mm tubes inside the crossmember, I just tacked that in to stop it moving before plating it all up.


Bill

but how did you alighn the drill so it exited top and bottom in the right place?
Nick

with discomfort and a just long enough drill, into the "box" then on through out of the box.

I do advise getting hold of a few LS (long series) drills in a small variety of sizes, for which you really need a goodish tool shop. If you drill a pilot hole through all the way you can then open up later on to finish the hole.

LS are quite expensive but you only need a small variety to do the pilot holes with.

I even have 4 x 1/8" LS's that are 4½" long which were bought for a project. Of course being a heavy handed beggar I only have four left of the original half dozen. The good thing is that after breaking them one of the stubs had enough spirals to justify cutting a new cutting edge so's I now have an-ex LS that is 3" long too.

mark the hole position after measuring the traditional two times

drill the holes in and out once

always keep drills sharp
Bill

Surely the top position isn't really that critical, as long as you don't go so skew that you come out of the side of the x-member, in which case you probably shouldn't be doing this osrt of thing yourself.

I must say all this is much more rigid than the x-member I got with my Toyota kit. With that installed I always felt the car flexed more than it did before.
Jeremy Cogman

When fitting the MMC reinforcing boxes into the monocoque crossmember.
I drill the chassis member at the top first.
Then fit a reinforcing tube, the size of the bolt diameter to be used, vertically in the reinforcing box at the appropriate place. The tube strengthens the box and avoids compression of the crossmember when the bolt is tightened.
Tap the tube into the crossmember until the hole aligns then drill all the way through the bottom of the crossmember. The drilled hole should be pretty square.
When the gearbox is in the car I offer up the chassis plate and spot then drill on the bench. On earlier conversions I used the MMC parts viz reinforcing tubes and chassis plate but have now made my own of the same design but of thicker gauge steel.
I shall probably, in future, substitute the chassis plate with one made from 10mm steel plate for no other reason than it wont hang down under the car so much.
nine conversions so far with no known problems or complaints.
Alan Anstead

This thread was discussed between 19/08/2008 and 21/08/2008

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