backplate drawing

[kevin s]

Does any one have a dimensioned drawing of the 1098 engine backplate?

I am working out how to fit an Mx5 gearbox in, it looks promising, the gearbox in 14" wide at it's widest point the gap between chassis legs is 16", the gearstick can be moved forward to a similar position to the original easily, I will use the minor flywheel and starter position and make a mount for a concentric clutch slave cylinder, hopefully I can squeeze a 1.6 mx5 clutch under the minor pressure plate.


I have the dimensions for the mazda gearbox, just need the minor ones so I can draw it up. (I am making one from measurements at the moment but if I go ahead I will probably get the final one laser cut)

[philthehill]

I would suggest that you obtain a 1098cc rear engine plate to use as a pattern. They are reasonably cheap and more accurate than any plan(s).
A 948cc rear engine plate is equally suitable so long as you make allowance for the fact the the 948cc plate is pressed steel and thinner. All the holes are centered the same whether it be a 948cc or 1098cc rear engine plate.
https://www.ebay.co.uk/itm/MORRIS-MINOR ... Sw-YxdAU55
You may have already made considerations regarding the Mazda first motion shaft and how you intend to fit and support it in the rear of the crankshaft or indeed if its length and diameter is suitable for the Minor crankshaft. If not they are major considerations.

Phil

[kevin s]

I have a couple of 1098 back plates but to laser cut it needs to be digitized, if it comes to it I will get one laser scanned.

The first motion shaft sits nicely inside the centre of the flywheel, I turned a bush in alloy to centre it on my trial plate, eventually I will either make a bronze one or a spacer to allow me to use a ford roller bearing.

Also wondering if I could keep the mazda clutch actuation and use a cable pulling it from the rear, need to have a look and see If I can get a cable on above the pivot or make an idler..

[philthehill]

What are the benefits of using a Mazda MX5 gearbox to that of a Ford type 9?

[kevin s]

£25 for a good one, they are a lot tougher. and I like a challenge

This is where I am at.

rps20200919_194823.jpg (150.6 KiB) Viewed 2247 times

n

Stood a engine on it's nose, shimmed the gearbox input shaft to remove all the play then dropped it over the pilot bearing mock up and drilled through the backplate. This back plate is a marina one and on the first attempt there were 2 problems, the marina flywheel touches the mx5 bell housing and the starter fouls the chassis leg. So attempt 2 is using the minor starter position and flywheel (welds And plate need grinding back) I'll also add some pieces to cover the 2 top holes. Obvoiusly the bell hoising will need cutting to clear the steering rack and starter. Then I will need to think about a X member and gearbox mount (the maxda doesen't have one)

[Declan_Burns]

Excellent project-something I often thought of doing. Laser scanning would be the easiest and probably the best way of doing it. If you need any help with the drawing I can offer assistance as I have worked with CAD systems all my working life and still use it daily.
Laser cutting is quite cheap nowadays and there are a lot of reasonable online services that I use regularly.

Regards
Declan

[kevin s]

Thanks for the offer we should be OK though my Son is pretty good on CAD and had had quite a bit of laser cutting done already.

A bit of background, about 3 years ago I tried the mazda box in the car with the starter in the marina position, this was the result.

rps20171120_153228.jpg (45.31 KiB) Viewed 2163 times

With the starter moved to the minor position this will be fixed as it will be the same as a regular minor.

In the end I converted the morris box to hydraulic clutch, this being the slave cylinder.

rps20180326_223524.jpg (57.86 KiB) Viewed 2163 times

And this the master.

rps20180401_000454.jpg (107.02 KiB) Viewed 2163 times

You can get off the shelf csc kits for the mx5 box but I will be doing something very similar to to how I did the morris.

Also will need to cut the bell housing like this.

rps20171120_153437.jpg (58.92 KiB) Viewed 2163 times

So it all looks pretty straightforward, the tasks will be

Cut bell housing to clear starter pinion.
Cut bell housing to clear steering rack.
Make csc mount.
Make trans bracket for gearbox mount.
Modify crossmember to suit gearbox mount.
Move gearstick forward.
Modify trans tunnel cover to clear box if needed.
Make or buy prop shaft.
Lengthen gearstick.

[kevin s]

Firstly a correction, the pilot bush I made fitted in the crank, it's the original mx5 one which goes in the flywheel.

rps20200921_193815.jpg (150.97 KiB) Viewed 2124 times

Collected a load more parts from my store today.

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The second gearbox is the one I first modified so it has a chunk cut out in the wrong place for the starter it is a mk1 mx5 box which means is pretty easy to move the gearshift 6 or 7" forward, the plan is then to fit the mk1 tail housing to the mk2 box.

The 1098 backplate is so I can finish the starter hole and the flywheel do I can measure up clutch.

[kevin s]

Some progress, shifter is now in the same place as a Morris minor, hopefully this will mean no need to modify the tunnel cover.

680c9198d527_m.jpg (142.1 KiB) Viewed 2091 times

Also decided it will be easier to add a second bolt in crossmember further back than the original which then lines up with the two tapped holes on the rear of the tail housing, might be a fiddle getting a nut plate past the master cylinder but not insurmountable. Only real issue now is making a clutch work, options are:

The 200mm mx5 clutch under the minor cover.
Somehow skim 5mm off of the outside of the mx5 clutch
The complete MX5 clutch (looks about 7mm larger than the flywheel)
Find some other 200mm cover which will fit on the minor flywheel
Build a hybrid disc with mx5 hub and 190mm minor linings

[Matt]

Have you offered up the MX5 clutch plate to the flywheel and the 1098 cover? There is often spare space around the edge of the friction material and it might just about work without any mucking about?

[ManyMinors]

A most interesting conversion. I think the Mazda gearbox gives a much more pleasant gear change than the Ford one and is much more readily available at decent prices too. The Ford gearboxes will be in short supply soon.
The old Toyota 5 speed box conversion was a very successful one but again, available donors became hard to get.

[win]

I am following your conversion with great interest, and thank you for sharing. Watching your progress with anticipation.
I cannot understand how you moved the gearstick forward, did you use the MK 1 box and moved the stick housing forward, and re bolt it to the casing, after cutting the selector shaft down to length.
Where are you approximately in the country? did you obtain all the old clutch parts you needed.
Kind regards Win

[kevin s]

Have you offered up the MX5 clutch plate to the flywheel and the 1098 cover? There is often spare space around the edge of the friction material and it might just about work without any mucking about?

That's going to be my first thing to try fingers crossed.

[kevin s]

I am following your conversion with great interest, and thank you for sharing. Watching your progress with anticipation.
I cannot understand how you moved the gearstick forward, did you use the MK 1 box and moved the stick housing forward, and re bolt it to the casing, after cutting the selector shaft down to length.
Where are you approximately in the country? did you obtain all the old clutch parts you needed.
Kind regards Win

I'll add a description of how it's done later.

[kevin s]

This is how I moved the shifter.

This is the original position

rps20200923_175539.jpg (127.17 KiB) Viewed 2048 times

Cut the front of the shifter off to give this.

rps20200923_175614.jpg (142.19 KiB) Viewed 2048 times

The easy option is to move the rear holes to the front position this moves it forward 103mm.

rps20200923_175414.jpg (136.24 KiB) Viewed 2048 times

This not far enough though so took it as far as it would go 156mm forward.

rps20200923_175646.jpg (217.73 KiB) Viewed 2048 times

Filed the top of the case to give a mounting of the correct height.

[kevin s]

Next up was drilling and tapping the case for the 2 bolts to attach this.

rps20200923_175838.jpg (138.88 KiB) Viewed 2043 times

Next was shortening the shift rod, took a piece of bar and drilled 2 parallel holes 156mm appart

rps20200923_175956.jpg (136.39 KiB) Viewed 2043 times

Pinned the rod to one hole and welded a nut next to it (just the nearest bit of metal I had lying around).

rps20200923_181715.jpg (125.63 KiB) Viewed 2043 times

Moved the shaft along, pinned it to the other hole then clamped the bar to the nut and turned it over, then drilled through the second hole in the bar and voila 2 parallel holes 156mm appart.

rps20200923_180044.jpg (88.4 KiB) Viewed 2043 times

[kevin s]

Cut the rod off trialed the shift mechanism on and all seems well.

rps20200923_180147.jpg (131.65 KiB) Viewed 2043 times

Made a bracket to support the rear of the shift housing.

rps20200923_181641.jpg (79.75 KiB) Viewed 2043 times

Shortened the shift rod tube.

rps20200924_191224.jpg (139.88 KiB) Viewed 2043 times

And a trial assembly proved it all works OK.

rps20200923_180218.jpg (142.05 KiB) Viewed 2043 times

I can't finally assemble it because I have lost a ball bearing out of the shift mechanism (new one on it's way) and need to get some sealer (no gaskets in this transmission). Once this is done I will finish the backplate.

[win]

Thank you for your detailed description, much obliged.

Regards Win

[kevin s]

Moved back onto the backplate, cut some pieces of steel out to fill the missing bits, tapered them and welded them.

rps20200926_175905.jpg (160.18 KiB) Viewed 2001 times

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rps20200926_180001.jpg (150.31 KiB) Viewed 2001 times

This is it with the 1098 one on top.

[kevin s]

Then filed out the starter motor hole using the 1098 one as a guide.

rps20200926_180143.jpg (153.81 KiB) Viewed 1999 times

Cut just enough out of the clutch housing to clear the starter.

rps20200926_180245.jpg (165.16 KiB) Viewed 1999 times

Plan is to make a steel cover to go over the area and rivet or bolt it in to return some strength.

Also tried using a slitting disc on an old clutch which cuts it supprisingly cleanly, therefore it may be possible to trim 5mm off the outside of a mx5 clutch by mounting the disc in the lathe and trimming the outer diameter.