1968 Singer Chamois (Yamaha R1 Powered) LPV433G

I’m back…5 weeks ish before the retro rides weekender 2022 so I best make a start on some much needed updates. My aim is to take the imp around the Autosolo on the Sunday if I can. I took the BMW 8 series around it last year and blew up the gearbox trying to do a burn out in the stop box! It was a lot of fun but the Imp should be far better suited.

I have already started on the Imp but there’s still a lot to do before the show. The problem with leaving my updates so long is that there's a lot to write up on...

Roll Cage....
The front half of the roll cage I ordered last year arrived back in January.




I checked it fits but other than that it's not fully fitted. Just need to clean up some metal and fettle the feet and weld them in. The door bars will wait for another day. I was really worried the amount of wheel arch and floor I had cut away (to make the wheels clear) would mean it wouldn’t fit but it looks to be all good… just about.







Diffs...
I best update you on some thoughts and processes that have happened since my track day back in December with regards to the diff.

The propshaft boot was destroyed at the trackday and threw grease everywhere! So this needs a redesign.



We all observed the hideous gearing that was evident at Donington Park.

The RX8 diff I used (because cheap) was confirmed to be a 4.444:1. My initial calculations suggested it would be fine but clearly not. So working backwards and with the speed I thought I was doing plus a load of research lead me to MX5 MK3 diffs. The MX5 MK3 guys use the RX8 diff as an upgrade when running high power (because the diff is hench). So I planned to do the reverse of this by using a smaller (lighter) diff with more available ratios would be perfect. I sourced a LSD 3.7:1 ratio from a MK3 MX5 (the tallest ratio they made). Theory being it shouldn’t be much work to convert from one to the other.

Once it arrived it was obvious that it was going to be more work than initially thought. The black diff is the RX8 diff and the rusty one is the new MX5 MK3 diff.

Current mount holes I use were blanked off.






Driveshafts we’re smaller so I bought a pair of those to make new.



The top two studs used to mount my reverse motor were of a different offset so this didn’t work.



Anyway I’ll stop here because it was all a waste of time. All of these issues were fixable but this diff only gets me to ~116MPH top end. Which is not enough.

Embarrassingly it finally occurred to me that the clutch basket on a motorbike engine is not on the end of the crank. Therefore there must be a gear set between the crank and the clutch. It turns out these are not 1:1. They are more like 1.5:1 so this whole time I had my gear calculations a good 50% off target. It turns out I was limited to ~92mph at Donington but hey it was a good ratio for the RRG21 Hillclimb!!

So what next you ask… going with the theory that I’d like this car to be useable on the road without being completely obnoxious. Top end numbers were not the priority. I didn’t mind if I never used 6th gear on a track day… so long I had an ‘overdrive’ that would be good.

I found that a diff from a BMW 1 series could go pretty tall on the gears while also not being massive. I bought a diff from a 2014 116d that had a ratio of 2.65:1. This gives a 70mph cruising speed doing 5000rpm which is respectable.

These diffs and driveshafts are also dead cheap. Diff and shafts for a grand total of £55.92 delivered!



Major issue is that this diff is not really that cheap in the grand scheme of things.

This diff is an open diff. To fit an LSD is going to be pretty expensive but we’ll cross that bridge another day. I’d like to prove this ratio works and we can go for the upgrade later in the year by fitting a gripper diff or some such. With the correct corner weights it will still be good fun.

The first job was to cut off the standard ear mount as this is no use to me.










I then made a starts of a new mount using 4 casing bolts.






Next I started to adapt the input shaft to accept my prop.

I took the tri-lobe mount off that was previously used for the rubber donut and made it interface with my BMW cup.













I cut the RX8 splines off the BMW cup and had to add some material and do some lathing etc to get it to be concentric. Ideally I’d have added more material but the craters you see are purely cosmetic and doesn’t make a bit of difference.











I then changed the PCD of tri-lobe. Plugged the holes with the welder and attempted to drilled the new PCD. I had to use the reverse gear as my guide. I aligned it all with the concentric assembly and tacked the reverse gear to the tri-lobe.









Not my cat….. 



Top tip, I was having massive trouble drilling the plugged holes even though I didn’t quenched them or anything. My drill bits were sharp and of good material but they were still not cutting it. I heated up the lobes as hot as I could with the blow torch and left it to cool naturally. This annealed the metal and it drilled out easily. Such a difference.

I'm now able to trap the reversing gear between the cup and the tri-lobe while all being concentric. No more nasty spacers.


This weekend.. I squared up the diff on the bench and then welded on some datum points to try and aid me aligning it in the car. I still ended up getting the engine crane in to act as a third hand. With the diff positioned as best I could I cut some box to tack in temporarily as my metal order hasn't arrived yet.









At least I was able to get on with the new driveshafts now. A bit of a problem I didn't realise until they arrived is that the 1 series driveshaft uses floating CV joints at both ends. Where as my old setup used one big pot joint and a fixed outer CV. This means length change during travel will be limited.

I cut my old shafts in half and tried to get the pressed in stubs out of the MX5 (MK2) halves (outers). One came out after a fight but the other had to be redrilled. I ended up making a bed support and then using my boring head in the tail stock. Hey. It's not stupid if it works. I also reground the big chamfer ready for welding.















Working out driveshaft lengths then developed into a bit of a nightmare. First off you could see the angular motion of these CV's was not as great as the old pot joints. At full droop the new shaft didn't point to the centre (or lower than) the outer CV. We thought about lowering the diff but this would be bad for the propshaft and it's boot. The droop or at least the total travel seems to be excessive anyway so limiting droop seemed to be the best solution. I didn't want to move the shocks as these are set for limiting bump. Idea is I'll simply add some limiting straps in the old shock mount points. It’s not ideal but I don’t plan on going dukes of hazzard too often.

Working out driveshaft lengths go something like this:



Total CV Travel = 24mm
With flex in bushes etc I wanted a Safety Factor (SF) of 10mm both ends but that would only leave 4mm for length change! So I reduced this to 20% which is 4.8mm leaving 14.4mm of length change through travel.

With the car on axle stands and measuring from the floor.
Full bump = 740mm
Target Ride Height (by eye based on nothing other than how much tyre was on show) = ~670? Can be changed if needed.
Droop would need to be limited = 625mm

Giving total travel:
Bump = 70mm
Droop = 45mm
Total sweep = 115mm (plenty)

Stupidly I did all this on the RHS which is the long driveshaft. The LH short one would naturally have a bigger issue with length change.

The numbers were the same (transferring measurements to the car body rather than the floor). With the exception that droop needed to be further limited by another 20mm. This left a current theoretical droop of 25mm..... lol. Maybe the cars look and nominal ride height might need to be lowered to be more within the middle of the sweep range. People like a stanced Imp don't they? Lowering the car another 22.5mm shouldn't be that bad so long the sump is still ok... it will be ok. Especially with the new springs I'm sure it will be fine.

Once the dimensions were settled on I made the driveshafts. A bit of repeat content for you. Cut, drill, dowel, press, weld. I will fully weld them once the diff is fully mounted, just in case.














Springs...
A few months ago post Donington and after corner weighing the car we removed the rear springs to see what they are. On the press with a corner weight scale under it we compressed a small amount, zero’d, then compressed by 1” and took a reading. We measure these to be 600lbs springs! And the car was still soft of the rear. Shows what an engine hanging out the back and a short leverage ratio does to the spring rate. Anyway we thought a 800-850lb spring might be about right but I decided to go for a 900 to make a real step change. We can always dial it back right…

I went for a 7” long spring as I had to use helper springs with the 6” ones just mainly as spacers (they were coil bound with no weight on) Anyway new springs arrived and they're pretty chunky, who’d of thunk it.

Very busy indeed!

On the BMW diff front it shouldn't be too tricky to get an LSD in there. Looks like a medium case diff from the look of the casing, so you should be able to get factory LSD cores from E30 325i/E28s/E24s/E36 M3s (clutch type), or Z3 2.8/3.0s (torsens). There might be differences with CROWNwheel bolt patterns, but not sure about those.

If you do need an aftermarket one then I've heard good things about Blackline as a Quaife alternative. They do helical diffs for lots of different BMW diffs. The only point of difference is you have to drain the diff oil after it's bedded in a little, so it sounds like they outsource the final running in of the gears to you rather than do it in house. Probably how they can offer a lower price than Quaife.

I’ve just spent 4 days solid on the imp and made some good progress. Technically this was my last weekend before the show as I’m busy next weekend but there are plenty of evenings between now and then. Although that’s only like 2hrs each night by time I get home from work. Annnyywaay….

What I have I got done…

First job was to fix the front ride height. Even on its bump stops the height was still higher than the target ride height of the rear. Big negative rake angle, not cool. So I set about slamming the front. I changed the design of the top mounts to drop the bump stops by 30mm ish. This put the wheel right at the top of the inner arch tub.

This then causes all sorts of issues with steering and roll clearance. I only tubbed the car enough to clear at the ride height I was originally working to. So I’ve had to cut and do nasty things to what was a finished area. Anyway ugly stuff now allows for full lock to lock to bump.. well good enough. I’ll fix the scars at some point.



Moving onto more important things… now my metal had finally arrived… I was able to get the diff mounted. I started with the obvious bars to get it fixed in secure. I then removed the support bars so I could refit the exhaust and then make bars to avoid this.







It’s just my luck that one bar would want to be bang on where the exhaust runs. This wasn’t too bad as I needed to invent a new way of mounting the reverse motor anyway so this could be incorporated.





I parted off the old mount flange to recycle the face plate. If you remember I had to get this on the mill to bore out the main hole ID so I didn’t want to re make this. A cheap band saw is hugely recommended for anyone starting out. It’s one of those tools that you never need but when you have one you can’t live with out.



I cut a hole so this plate could pivot around this diff mount.



When bolted on I was able to set the engagement depth as well as it’s offset from the gear.



I packed out the pinion to give me the full thrown out length and offset the engagement by using a bit of blue roll in the teeth haha. I checked it all with some squares and tacked it in place.



This new motor position didn’t have much resistive strength against the torque reaction. I decided it’s best to make a removable brace to keep it engaged with the gear. It only has to move a few millimetres before it starts to slip out and grind. This bar needs to be removable so it’s easier to take the diff in and out. This all took quite a lot of time…



I then made two more bars up to the main diff mounts.





I added one cross brace to the main frame as I’ve removed all the old RX8 diff mount bars. This would have been an full cross but the exhaust hangs very low and I’m not re making that now.



Diff was out so I can fully weld the frame. Not pretty but access was a bit tricky and clean up was impossible.

With the diff out I can look at adding the oil feeds and moving the breather etc.



With my best judgment I ground a flat near the second bearing. The target is to get the oil feed bang in the middle of the two bearings… the hump/ridge you see if the start of the rear bearing.



I started with a pilot drill but it suddenly went from drilling cast iron to something more solid so I stopped as I can only assume I hit bearing. The only option was to try again nearer the rear bearing. This worked out fine I went though to the main shaft with out issue.

Then it got a bit weird. I went though with a larger drill and a cavity opened up only on the rear side of the diff. The oil channels in this diff are quite fine and looks like there is a clear route that is should follow.



I proceeded to open the hole out to full size thought to the main shaft. All oil paths now lead south down to the sump as this was the oil feed. All drilling was done upside down btw to ensure most of the swarf fell out as much as possible.

I tapped the hole but unfortunately due to the void there were full threads on the one side and next to nothing on the other. I fully caked the barb with loctite and it will be fine.









Next target was the drain/outlet feed to the pump, going into the back plate didn’t make sense on this diff so I aimed for the lowest part of the main pumpkin not in line with the CROWN wheel.

Again drilled and tapped. I won’t fit the barb until the diff is in the car as it’s rather exposed here and will probably get broken off on install.







Next I moved on to the breather. The stock breather was a very small hole so I drilled this out and tapped it to plug it with an M4 button head. The obvious was to move the breather to the fill/drain plug like on the RX8 diff but this was a big Allen bolt rather than a standard nut. I opted to go for stealing the breather from the RX8 diff and simply sticking it through the back case up high.







I got it all painted looking good…






Next we move onto the propshaft… I bought a silicone hose humped coupler as it looked to do the job nicely but in reality this was too stiff and no good by time I cut it down to length it wasn’t going to work.



I did however know my solution would be externally mounted and would need some detail to clamp over so at first I tried to simply build material and weld on an external flange. This was really ugly and I decided to do something better.



I ended up cutting the centre return detail out of the stock boot cups and turning my own external flanges. I welded these in and then dressed them back in the lathe. It turned out pretty nice in the end.







I then had my eyes on the redundant RX8 driveshaft boot and stole the main ring out of this. The minor OD was within 1mm off the stock boot flange OD so this was almost perfect.





Test fit and then trimmed down…



I got the prop all assembled and packed with new grease as I lost all of mine!



I got the back plate sealed and bolted on with the new diff mounts.





The assembly process of this diff was far better than the old diff. Prop and reverse gear on.



Diff in…



Reverse motor on and brace bar in.



Oil lines attached and diff filled with oil.



Time to preheat the driveshafts as there’s no going back from here.



Both shafts splatted with weld…




And back in the oven to cool slowly. I checked on this an it took about 1min per degree to cool which is nice an slow hopefully to help normalise everything.



While those cool I looked at the remaining roll cage foot.









I didn’t fully weld the front edge as I believe I still have some arch work to do here so it’s a lot easier to not weld it now and then fix it later.




While that paint dried next up was bonnet pins. At Donington the bonnet would unlatch itself and I’d have to pull into the pits with the bonnet bouncing on the safety latch. Not cool. Bonnet pins was a must not for safety as I plan to keep the stock latch and safety but so at least it’s not bouncing up every 5mins.

I’ve pondered over the location of these pins for ages and had a few people’s input. Do I align it with… the head light? Or put it in the centre of the panel, ie edge to bonnet crease? I even proposed right in the corner, centre of the bonnet radius is the pin?

Anyway in person I went with in the middle of the panel details. This bonnet is basically scrap anyway so if we don’t like it we can change it.



I bought a nibbler purely to do this job and it broke instantly. It did about 2” then broke. That’s going back.



Anyway attacking the the angle grinder I love the layers of paint and filler this car has had. This car would be so much lighter with out 5 buckets of filler in it. Every panel I touch has filler in it!



Anyway I got them sunk in and bolted up.





Local cat inspector Tom arrived and said they should have been further back and out but I disagree.



That’s all for now. I have quite a lot of evening work still to do…

I had exactly the same problem with those nibblers. Probably only good for very thin ally or McVities Digestives after being dunked.

Wait, you've been doing all of this cutting about with 3mm grinding discs?

First off, bravo! Makes it all the more impressive.

Second, get some 1mm discs

Just checking that you've come across knotted wire wheels and sanding flap discs as well. Both also game changers. Oh, and I've also recently discovered stainless shrinking discs for angle grinders which are brilliant for sorting out panels that have warped due to welding. They're a little more expensive, but you only ever need one. If you can get a 9" one then that's ideal, but I've used my 4.5" one to great effect. They work by selectively heating high spots with friction which you then cool with a spray of water and it shrinks that section down to flatten a panel.

Lol fair enough!

What have you used to secure the CV boots there, is it welding wire? I'm interested to know how well that works, as I loathe buggering around with those steel ties.

Its old copper wire left over from when I rewired the house. Wrapped around 3 times pulled tight and then twisted up like lock wire. I then bent this flat in the opposite direction to the shaft rotation so if it catches on something it just gets knocked flatter. I only used this as I didn't have any lock wire to hand and mig wire goes rusty but I have also used this before. I've also tried metal cable ties but they just don't hold any tension and are rubbish but they look the part.

Sunday Afternoon Autosolo booked and paid for.... 

There's a gun?! This might be why they don't work that well for me! Gonna have to get me one of these...