looking at where it cracked, there's lots of things that could have had something to do with it cracking there;
bolt next to the crack tightened a bit too hard, worn subframe-engine mounts etc.

what i don't believe is that it failed due to worn gearbox mounts or by the clutch lever. it's a radial fracture so it ripped this far due to engine torque; the big question is did it rip from day to day or at once. does the aluminium have a tiny different (more oxidized) color near the clutch lever or anywhere at all)

It could be failed (or insufficient) engine mounts causing the engine to twist relative to the drivetrain, or it could be he's hit something on a rally that has weakened the bellhousing causing it to fail later.

I might just stick with my standard 1.4 then. that looks bad

I have had more beer.... and think I've got it.

F7R has a huge head casting compared to B172k, as well as having a longer stroke (so more balance weights in the crank) and more piston size. All in all, I reckon almost 20kg's difference. My rear engine mounts are tired (you can wibble them a bit with one finger) + engine being heavier means everything sits lower at the back than it should. So, the front mounts are where they should be, the rear mounts are low, meaning the tail piece of the bellhousing is pointing downwards. As our props have no UJ's, only rubber bits, I reckon the prop was holding the back of the engine up a bit (at least, there was a loading on the prop downwards and output shaft from prop upwards).

That is what took out my 228,000mile prop 4 weeks ago. When I put on my new prop (a nice sexy low mileage one with good solid rubber bits compared) the force was now pushed down to the bellhousing casting, and as there is only fixings between the bellhousing casting between 9 and 3 oclock the casting was hugely stressed around this point (the circumferential crack seen in this pic...


So, either a prop with a UJ and built in length adjustment is needed (i.e. the same as everyother car ever) or a set of more heavier duty rear engine mounts.

I'm going for both, might have to go custom on the rear mounts too but I was going to get a custom prop anyway. I'm currently thinking I'll get a CV joint fitted instead of a UJ though, due to the difference in angles at engine end and gearbox end... (engine end is 2x gearbox end, UJ's in pairs should always be used with equal angles else you get weird effects).

Right... more beer now.

Coukd you not go double cardon on the Ujs??

My Dana on a 5.0 Bronco runs Ujs on front axle and props without issue.

Easier and cheaper to replace as service items than a Cv I'd have thought.

Or, make new rear engine mounts sitting on a cradle welded to the chassis rails.

sven360 wrote:Coukd you not go double cardon on the Ujs??

My Dana on a 5.0 Bronco runs Ujs on front axle and props withou tissue.

Im guessing Coukd is northunmbrian for Cooked.
Dana is a little irish lady?
Dunno what cardon is. Maybe short for cardigon.
U.J.s are robably universal joints?
And tissue is like skin, human meat or toilet roll.

All in all, I do not understant any of this.


Good sleuthing though Chris. Looks like youve cracked it. (pun intended)

volvosneverdie wrote:

sven360 wrote:Coukd you not go double cardon on the Ujs??

My Dana on a 5.0 Bronco runs Ujs on front axle and props withou tissue.

Im guessing Coukd is northunmbrian for Cooked.
Dana is a little irish lady?
Dunno what cardon is. Maybe short for cardigon.
U.J.s are robably universal joints?
And tissue is like skin, human meat or toilet roll.

All in all, I do not understant any of this.


Good sleuthing though Chris. Looks like youve cracked it. (pun intended)

Cleverly edited.
Methinks the lady doth protest too much

Possibly Sven, I've not looked into it properly. TBH, big spinney things this size are well out of my territory, so I think it's time to ring someone up and actually pay for some advice. Bit against the ethos of not doing it myself really, but

Rear engine mounts shouldn't be too bad. Lots of shear loaded mounts exist for different industrial apps, it's just finding one the right size. Or working out why they are shear in the first place and why not just mount a normal cotton reel bush there. Might have to do some simulations.

*Looks at chris paying someone to do work on his car*

*Looks around for 4 horsemen*

Speedy88 wrote:*Looks at chris paying someone to do work on his car*

*Looks around for 4 horsemen*

^
If he cleans it too,
Im taking tinned food underground.

Right... time for some updates I guess.

Only small ones atm, I've been doing lots of designing and not a lot of making, but hopefully going to sort out this problem properly. Designed lots of new engine mounts that are awesome in most respects, but none that solve all problems yet. Will get there.

Still, in the meantime, I've been collecting/making parts to put everything back together with. New bearings engine side(spigot, clutch release, bellhousing output shaft) caused some issues, the clutch release bearing seems to be pure unobtainium at the moment. I was about to make up my new version on the 4 axis CNC to take a standard 7206 when 10 clutch kits came up on ebay for not silly money. Grabbed a few of those for now, will make the new bearing carrier when time is a bit free-er.

Same with engine mounts, I could carry on designing for ages, but until I'm sure what to design around it's a bit pointless. So, I rang Dai up and got him to send me some new mounts.

But... I needed some thing to tell me what was going on, as all I had was assumptions. So, I made a new Chris' Special Tool, the CST002.

With Friggin' Laser Beams

The CST002 is a lump of an old torn apart propshaft, where the spliney bit has been removed from the sleeve bonded into the rubber with an eleventy ton press. They are pressed in there pretty well, it needed all eleventy tons and shot across the room. Add to that one laser pointer and lathe up a lump of something to hold it all together (I used PEEK with adjustment grubscrews, as I had both to hand).

The CST002



Then, slide the tool onto the gearbox input shaft and turn the on-off switch (cunningly disguised as a cable tie) to laser-ise


As there is a small amount of run out in the laser pointer that I didn't take out (needs another ring of grub screws) rotate the input shaft to describe a circle, the input shaft is pointing to the dead centre of this. Here you can see where the gearbox is nearly spot on, the break in the circle is the laser being projected on the clutch output shaft, the main 3/4 of a circle is against the bellhousing


So, now to try the other end. This is more tricky, as I havn't yet connected up the clutch, I can't rotate the shaft, but I can get a good idea of whats going on. Currently on old mounts, for a comparison. Mounts mounted half way up the slots (which I never do, just put it in quickly in the dark last night and this is where they happened to be when I looked)

Place on the clutch output shaft

And the point, which could be anywhere on the previously seen circle


Not as bad as expected... high, so, lets put the engine mounts to where they should be.



And where is the point... pretty much spot on... hmmm


So... what can be concluded...
Well, nothing at the moment really, statically everything looks pretty good, I'll hook the clutch up later (I've filed some of the nylon spacers, so need to make some more) and do a circle test engine to gearbox direction.

The next thing is dynamic loads, both times something major has fallen apart has been under very hard acceleration and on stock mounts everything does flap about a lot. So, I need a way of mounting the camera to the car so I can shake the engine without moving the camera relative to the car. Preferably with the engine spinning. Will plan that test when I get another free minute.

This is cool. And well done to you.

More testing this weekend, but lacking pictures.

The explodination has wiped out my clutch cable, but pretty much everything is plumbed up now. Really want to get back driving this now, Corsa love can only stretch so far

Nice work on the laser pointer! very useful! bet you cant wait to get it back. Im going to look into laer alignment when I do my swap, dont want everything packing up just after I put it in!