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Thread: Gearbox Fettling...

  1. #1
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    Gearbox Fettling...

    Hi guys - it's been ages since I provided an update on the Green Machine, but I have been getting all oily today fettling my new 1.2 Ti gearbox, which I bought from one of my colleagues over on Alfa Owner a couple of years ago.

    Since receiving the gearbox I have cleaned up the castings with dilute hydrochloric acid, etch-primed the surfaces and painted with a proprietary wheel paint the same colour as gold anodising (the actual colour is Rays Racing Bronze, it is used on Scooby wheels apparently), before having the whole gearbox clearcoated and cured in a low-bake oven.

    I have also obtained an Alfa 145 cast alloy sump from my friend Graham to replace the pressed steel item used on the Alfasud. This has cast cooling fins and is heavily profiled so that it conforms very closely around the differential crownwheel, which prevents excessive power loss through oil churning. Graham suggested I run the sump without a gasket to prevent "squirming" under load, as the Alfatune engine destined for the Green Machine will probably be putting out rather more torques than my current 1.5 Ti unit!

    So I needed to check the clearance around the gears with the 145 sump dry fitted. I stood the 'box on end so I could undo all the sump bolts, and slit along the gasket line with a Stanley knife to make sure that no paint peeled off the casting, which it didn't. I removed the old gasket and the internal cross-brace (which can't be used with the cast sump), and made some measurements. The only possible problem with clearance I found is around the differential itself - the crownwheel is slightly proud of the casing, so is below the gasket line. Fortunately, this coincides with the deepest rebate in the sump casting, which extends around 3-4 mm below the mounting plane. I offered up the sump and secured it with two of the set screws. Here's what it looks like...



    Bottom view...



    Right side view...



    Left side view...

    I think you will agree it is a thing of consummate beauty!

    With the sump plate in place I selected each gear and while holding one drive flange steady rotated the other to make sure the crown wheel and other gears were in motion. There was no evidence of scraping sounds while the gears rotated, and after removing the sump I could find no evidence of witness marks anywhere on the casting.

    However, as I was cleaning up the oily mess on the pallet, I noticed this roll pin...



    It's 15mm long. The sides of the pin have evidence of scoring, so it has clearly been used. My guess is that it is one of the old pins that was replaced during the rework at BLS and wasn't noticed before the sump was sealed. So I had a good close look at the gears...



    I've been counting up the roll pins in an Alfa gearbox and there appear to be 6 in total - four pinning the selector levers (two of them visible in this picture) and two holding a bush onto the main input shaft. Loss of any of them would result in failure to select gears or drive, all of which check out fine. According to Kev the gearbox only did 100 miles before he got fed up with the high revs and swapped it for a Green Cloverleaf unit. I rotated all of the gears to check for damage or missing teeth, and they all look fine, so it looks like the loose roll pin must have stayed in the sump throughout. How lucky is that?

    Lauren
    Last edited by Spacenut; 10-11-2013 at 09:58 PM. Reason: Trouble with my IMG links...
    only Pythagoras can save me now!

  2. #2
    Alfa bits are just inherently prettier than anything out of a Ford Focus.....!

  3. #3
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    I gather that fits well with your custom chassis etc, how well would that fit in relation to the bug chassis?

    come to think of it, were there any plans available to build a tube chassis for a nova? or would I have to ask the US NovaRX guys for the specs?

  4. #4
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    Without machining the casing to enable you to flip the differential, you wouldn't want to put this on a Bug chassis because you would have 1 forward gear and 5 reverse gears. The Alfa transaxle is also quite fragile, remember Hewland started off using the VW case with their own internals - much more robust!

    The 1.2 Ti has the shortest gear ratios of any gearbox in the Alfasud range, as it was designed to provide good acceleration in a sporty derivative (Ti stands for Tourismo Internazionale), but with only a 1200cc engine with 65 bhp. Its previous owner got so fed up with the engine revving away in his Alfasud that he swapped his box for a later Green Cloverleaf unit, which has more sensible ratios. However, with my 15" wheels and tall profile tyres, the 1.2 Ti ratios give me gearing virtually identical to a Green Cloverleaf with 13" wheels, so for me, its the one to have!

    Unfortunately the 1.2 Ti is also prized by racers, who treat them mercilessly, stripping the cogs and then thowing them away. They are getting rare now.

    Sterling Sports Cars are the only company currently offering a tubular frame chassis for the Nova. It's unlikely that you would be able to buy the plans. We think that Sam Cobley made three tube frame chassis in the mid-90s, but to my knowledge none was built up into a running vehicle. The factory demonstrator Mk4 bodyshell (no chassis) was rescued by Alex from the scrapyard, and is now part of his extensive mould mountain. One chassis is with a Nova club member, and another turns up on ebay from time to time, most recently with an Alfa V6 powerplant, but still a non-runner. The chassis for the Green Machine was my own design, and although I am quite happy with it being my first attempt, has some features which I would not duplicate again.

    Lauren
    only Pythagoras can save me now!

  5. #5
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    considering the price bracket for a Sterling NOVA RX I will have to leave that option in the same fantasy land as winning the lottery... now, if I did win the lottery, I would definitely consider getting a custom RX built and imported ~dreams~

    As for the rest... oh well.

  6. #6
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    So you had to try and one up me, didn't you. lol

    As for a space frame chassis, you'd probably be better off to get your own designed and built there rather than import the one from the US. Here in Oz, there are features in that RX chassis which wouldn't pass our engineering regulations (namely rose joints & multiple part suspension arms), so you'd be better getting one designed for use in the UK rather than US. Also, some of us here in Oz tend to think that the RX chassis design needs more work, with some thinking it lacks torsional strength, I think it was along the diagonal across the chassis.

  7. #7
    ***Euro-Nova Supporter*** Spacenut's Avatar
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    So yesterday the rain stopped play, so I used the time to finish off the warning light wiring on the instrument panel, and bolted down all the Cannon connectors that I am using to interface into and out of the system. I've been looking in more detail at the Denso alternator that came with the Alfatune engine, and the sense wire is used to set the voltage reference point in the circuit, so instead of the regulator producing 13.8V at the output pin of the alternator, if I put the sense wire up at the main fusebox, the regulator will ensure that 13.8V is present at the fusebox rather than the alternator, effectively overcoming any voltage drop in the harness. Cool huh?

    Anyway, today the rain held off, so it was back to the gearbox. When we left the action on Tuesday evening the engine was out but the old gearbox was still in the chassis. Today I removed the old 'box and behold! An empty space...







    I wrapped the chassis rails in cardboard so that the gearbox wouldn't damage the paint as it dropped out of the mountings (I drained the oil out before I released the fixtures - the oil didn't actually look too bad).

    With the old gearbox finally free I was able to remove the gear selector lever, and while I was at it I swapped over the reversing light switch and the magnetic drain plug for the blank filler plug on the new gearbox.

    I stood the new box on its end and removed the sump pan, hopefully for the last time, had a final look around, cleaned all of the oil off the mating surface (ditto on the 145 sump), applied the sealant and waited for it to skin over before offering it up. Bolts fitted, progressively torqued to 10 lb/ft.

    I ran a tap through the fixture holes for the rear mounting bushes, cleaned them up and fitted them, together with the centre mount.

    I'm rambling - here is the result...













    I think it looks terrific. But there's more...









    I wanted to show that there is clearance between the sump and the chassis...





    Not entirely obvious, I know, but I was able to slide the cardboard protection off quite easily. If anything there is probably more running clearance around the cast sump then there was with the pressed steel one!




    Another out-of-focus image, but you can see how the fins sit nicely between the two chassis crossmembers.




    As I've mentioned before, the gearbox is the first thing people see when I open up the louvre. The colour might not be everyone's cup of tea, but you have to admit it does look good!

    More news as it happens...

    Lauren
    only Pythagoras can save me now!

  8. #8
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    I'm awestruck

  9. #9
    It seems kind of strange seeing the shots from inside the driver compartment with an open skeletal chassis and the concrete beneath it . Do you know how much the green machine weighs versus a VW chassis Nova, is there a big difference?

    Also in some shots (maybe the angle) the ground clearance looks really quite limited

    Overall though it does look awesome, and hopefully being an alloy gearbox casing the paint finish lasts for a long time to keep the nice contrast between it and the black chassis rails - great job
    Last edited by islandman; 23-11-2013 at 12:35 AM.

  10. #10
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    Bloody awesome.


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