Saturday 28 October 2023

Martha II - no more banana-threads

As I pointed out a year ago, in my first post on Martha II, whilst bearing a very German name (Matra standing for Marx & Traub), is actually either "heavily influenced" or a more or less licensed copy of a LeBlonde Regal 10inch/12inch. So why would such a reputable German manufacturer choose a US design, which has a strong emphasis on cutting all sorts of imperial threads? The answer lies in the very first customer. The newly founded German Bundeswehr was well equipped with a plethora of US-made tanks, which quite obviously, were equipped with pretty every imaginable thread, but metric. As they also were rather worn, mobile tank repair units were formed and these were equipped with exactly these Matra MDR2A lathes.

To make these lathes substantially more useful for use in a metric country, one of the oldest engineering tricks in the book was employed: slap on a 127 tooth wheel and see how you can turn that 8TPI leadscrew into something that can at least produce some vaguely useful metric threads. Unfortunately going down the metric route means that the Norton-box on the front can't be used. Still, in the end a very useful spread from 0.5mm to 7.5mm thread pitches can be created. (Special honorable mentions for 0.50, 0.75, 1.00, 1.25, 1.50, 1.75 and 2.0 pitches spanning pretty much everything one can find on regular and fine thread pitch metric bolts in typical machinery applications.) With that incentive in mind, I set out to make the metric feeds work again. 

A quick rummage through the boxes of small bits (and some large bits), revealed that the axles for the metric gear scissor were absent, one of the stub-axles on the tumbler reverse lacked a means of retention and the plunger of the selector was broken as well and a few small bits like missing shaft keys and the like. 

I started with the shaft keys, because I had to start somewhere anyway, it was Sunday and I had some stock in the form of a bit of angle iron available. 

In reality it would have been a pretty standard 5x4x25mm shaft key, as is available form any bearing store, which I suspect was part of making this machine somewhat metric, just like the spindle nose which sports a very typical (for the time) Din800 M33 spindle nose (M33x3.5mm).

As I had no drawings of what the original axles would have looked like, I sort of had to wing it and design them from scratch, with the only real limitations being that the slot in the scissor was around 15mm wide and the milled out groove on the back around 23mm, which made M14 a sort of logical choice. As all the other gears where held on with M12 nuts that was sort of a given as well. 

One of the things I absolutely wanted was to have a way to lube the gears internally, so the axle shafts were drilled out and had an oil-groove cut in.

One thing I had sort of missed was that the step in the rear was maybe good enough to locate and space out the gear on the axle, but it was definitely not good enough to positively locate it on the scissor. Then again as nothing on such a lathe is allowed to only serve one purpose, I chose some M16 nuts (the axle diameter is 17mm). Step one was to part off the M16 nut to the correct width.

Put it back in the chuck and use that same bit of M16 all-thread to align it properly and then bore it out to a nice press-fit on the shaft.

Which was quite literally a case of *tap-tap*. (And then tig-weld them in place, just to be sure.)

Getting the whole lot set up, requires roughly 3.5 hands, but once you figured out it goes: lower gear on the scissor, top gear-set on the scissor and then tighten the scissor once it is engaged, it is actually manageable. 

Now the geared head on the Matra isn't exactly quiet to start with, but the video only vaguely gives you an idea of the amount of noise that is generated by the whole gear train.

When trying to switch the tumbler around and into reverse I realised two things: The reverse gear only had stayed in place so far because it wanted to and the locating pin on the plunger was missing.

I decided against fabricating this stub-axle from scratch as it turned out not to be hardened and the only trick bit in making it work was how to hold it in the chuck to drill and tap it for M8.

A bit of M8 allthread loctite'ed into the stub axle and it was good to go again.

Which left *just* the plunger to get fixed and have everything working again. Except there was nothing *just* in this process as it took way longer than it even remotely should have. 

After some casual inspection it became apparent that fixing the old plunger rod was not going to happen, so I made a fresh one from 10mm silver steel. Except there were two other ones I made. One on which I ignored the fact that whilst it was an M8 bolt, it had a 7mm shank (no idea why) and the other one, also from silver steel, when finishing the cross slide was sucked in and this elegantly removed the whole thicker section.

The plunger testfitted without a spring.

And lastly two glamour shots - finally with the metal enclosure for the change gears reinstalled and rather unusual for me, with the chip tray somewhat cleaned from the majority of the chips.

Sunday 15 October 2023

Comrade Car - the final chapter (part 13)

 Final chapter, final stand, final piece of cake... sounds dramatic eh? Well, if you're just interested in that one answer did it pass - well yes of course it did, but it wasn't nearly as straightforward as you think.

At the end of the last post, lil' comrade looked pretty complete. As a matter of fact he was pretty close, but for example the front bumper wasn't bolted down and he was still missing at least one of his tow-hooks. (Sounds easy enough, but means you have finesse a bolt into a LARGE hole, to hit a nut, which from previous engagements with nature sits at a funny angle (should be perpendicular to the lower frame rail) and all of that will touching up those bumper mounts with a die-grinder.)

Nothing you can't fix with a decently sized Newtonian particle accelerator.


On to the next issue - so I dialed in the front wheel alignment as good as I could reasonably get it, but when I hooked up the steering box, it wasn't perfectly in the center position. No big deal, right? Well, that's one of the first times I actually messed something up. Turns out, not all splines are created equal and there's one, which should act as a zeroing spline. So in hindsight, I should have undone the lower joint and reset that one to be correct and not the steering wheel. 

Next thing on the list - the fog light. Mandatory on all cars overhere and if your taillights don't have one built in, well you have to have an extra one. The one installed is the original one, it wasn't watertight and thus was in absolutely incredible condition. (I bought a new one, but that wouldn't fit and was open on the backside, because it was meant to be countersunk into the bumper, i.e. it was no good for me.) With no real other options, it was a case of make this one happen.

As the actual lamp socket was so rotten it wouldn't hold contact, I decided to solder the +12V cable directly onto the bulb.

A lot less obvious, but swapping the hood latch (and thus the cable) would eventually mean a lot more fun with a locking mechanism, than I'd care to admit. My personal tip for this: get a 2mm clutch cable (highly flexible) for a motorbike and feed that into the original outer. Cable is a lot smoother than solid wire and with a proper locknut... well... it'll just work.

Next up was tackling the interior. Now if you don't like a bit of let's call it rather rustic charm of the Lada insides, this might not quite be the car for you. (Fun fact, Soviet propaganda saw this vehicle as a competitor to the Range Rover.) But it can get a bit more homely, if you fit some of the panels etc. Before that: spray everything down with cavity grease. Plenty of it.

Rear seatbelts installed as well.

And just to top it off (only to realise I had to take the rear bench out to fit that one), the rubber floor mat. 

The first testrun to a nearby petrol station was rather sobering. It would pop and stutter, hardly make it beyond 85kph on level ground. Admittedly I was shocked, underwhelmed and questioned this whole endeavor (again).

4 Bar, not great, actually pretty terrible, if one's honest. Speaking of honesty this gauge reads about 1.5 to 2 Bar low every since it was used to test the compression on a high comp diesel engine. Still, 6 bar isn't exactly the kind of compression to write home about.

Especially as the other ones are consistently in the 6 Bar range.

The solution in the end would be about as Soviet as one can imagine. Mumble a quiet "ah pizdec", flood all four pots with plenty of WD40 and expect miracles to happen. Guess what, it actually worked. I suspect that the rings were just stuck in their grooves and it has stopped running on three pots ever since. (The fresh plugs might have helped a bit as well.)

Copious amounts of cavity grease...

... a fresh set of brake pads ...

Unsurprisingly those pads netted some nice results.

... and a bit more tidying up should have Comrade Car ready for some fun with the authorities.

Only to realise that a battery hold down would probably go quite well with the man in charge. (Marvel at the elegance and sheer beauty of a bit of angle iron (zinc plated of course) and two pieces of M8 threaded rod. 

Surely a vehicle that has seen so much loving care can only do one thing at the inspection - exactly, it failed miserably and I even got shouted at for having the audacity to bring "something like this" to the inspection. I later on went to another garage, got a list of faults and started tackling them one by one.

Not a fault per se, but a fresh fan belt, because the one installed was way too short and "well" run in. 

As I had to take off the fan-shround anyway, I cut out one section in order to make room for the 38mm socket that is used to turn over the engine for when you want to adjust valves or the like. (Mind you this one is still handcrank-able.)

So what did Comrade car fail on:

1)rear brakes - rear drums have warped liners (but otherwise were working fine)

As I already had them off before, pulling the drums off was easy peasy.

De-rusting the locating ring and the mating surface, probably would have been sufficient to make them run true again, if you ask me.

In order to prevent this, a generous amount of ceramic anti-seize should keep things in good shape for a while.

2) rear shocks - well in all fairness, all four of them were as dead as Count Dracula and still rocking... To be fair, those red shocks must AT LEAST be worth five horsepower. (Also they had a rather dramatic effect as I suspect that the shocks installed include a slight lift and it handles rather stiff for a vehicle like this.

They look dead-nuts cool. Don't even try to argue. Also they were the cheapest ones available.

3) Front brakes - both the disks and lines (all round). Strictly speaking, there's not much to it, except that the disk is held on to the hub with press-in wheel studs. This could be a bit annoying, when you just want to do a quick brake-service, but as the old Comrade needed more love anyway. 

The important bits when knocking out studs: Put the nut back on proper, i.e. not just 1-2 threads but wind it down to the point where the stud is just 2-3 threads low in the nut (in order to avoid mushrooming) and use a BFH (big f*cking hammer) to give it a whack-a-holio.

Again, my opinion, at least part of the runout comes from the fact that moisture will get between hub and disk and as rust takes up more room than, well, no rust...

I debated with myself whether or not to use anti-seize there and decided against it, because it was dry to start with. To be honest in hindsight, it might have been a smart move.

Reinstall of the studs isn't too hard, just tap two or three lightly in place from behind and then use a spacer and a wheel nut with a ratchet (to be able to feel when stuff goes wrong) and pull them in tightly. "Full pull" comes by installing the wheels. Some people will only tap them in from behind, but if you bump into one of the studs with one of those incredibly heavy steel wheels, I suspect it would be rather easy to knock it back out. And sneaking that sucker back in, without taking the whole hub-assembly off once more, I suspect that could be a good reason for a dose of very flowery language.

4) Shocks and ball-joints

Getting rid of the old shocks was a case of take no prisoners. The lower bolt was no real issue, the upper one got to know Mr. 5-inch-anglegrinder.

The upper ball joint is relatively easy to do and you only have to jack up the lower control-arm and everything will (quite literally) fall in place. For the lower one a spring compressor would probably come in very, very handy. (I did it without and after seeing some videos, this was more the way you'd do it at the side of the road due to some catastrophic failure.)

5) Rubber brake hoses - probably the part I dreaded the most due to some very nasty experiences in the past. But, nope no real drama. This car is meant to be worked on and thus, not stupidly difficult. Mind you there's a longer and a shorter line on the front, clean up the hardlines where the nut will have to go and a spritz of penetrating oil won't do harm either. But no nasty tricks with blow-torches or anything. 

6) It needed new tyres. So it got "new" tyres - actually they are off a newer Niva 1700, because the owner swapped them out for some real offroad tyres. 

And just like that, Comrade Car passed. 

Just like that? Well, the moment the engineer hopped into the car and drive it from the parking lot to the inspection booth, this happened:

With the inspection and registration passed successfully, I found a rather simple (yet not quite cheap) way to fix fuel gauge - a filled tank does wonders.

29 liters later the gauge showed full and that was the end of the "broken" fuel gauge. In hindsight this also means that realistically the fuel consumption was around the 12-14L/100km mark, which is pretty good for a carb'ed Lada Niva.

And then there was a bit of this - see where that gravel road takes us that I passed by at least a hundred times on my way home. 

So why the dramatic title? Well to be honest, I put it up for sale, not expecting much and then someone came, bought it and now...

So what's the verdict on the Lada. It's complicated and thus I might write a separate post on the subject. Maybe also it'll take a bit until that happens.