Racks and tacks
Entry posted by AdamR
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Not had much chance to get stuck in recently due to work being busy, but can't complain. Have had a lot of time to think about stuff though and work things through in my head, which helped when I did get a few hours at the weekend.
Things will quieten down at work now after Xmas so hoping to make better progress... although I have just taken on two engine builds and (pretty much) a full MX-5 race car rebuild to be completed before early March so we shall see :lol:
Anyway - bits I have done:
Ended up with 3 steering racks. A de-powered MX-5 one, a 2.4 ratio Escort Mk2 one and another from a Mk1 Golf. There were a few considerations for each of these - mainly distance between tie rod ball joints (bump steer), weight / simplicity and amount of rack movement per 360 degree turn of the pinion.
The standard Mazda rack gives 44mm per turn which is a 22.5 deg turn of the front wheels when the length of the steering arms on the uprights is worked through. I want something a little faster than this ideally, and it was too far between ball joints (about 640mm, I'm after 580-585mm) - could be chopped down to suit though.
The Escort rack offers 52mm per turn (26 deg at the front wheels) which is pretty quick... maybe a touch too much when combined with a fairly small (300mm ish) steering wheel, but it is very light / simple and has a good ball joint distance of 583mm. I need to investigate these further but it looks like I may be able to slightly tweak bump steer by adjusting the position of the inner tie rods on the rack. They are locked off with collars at the moment but have a pin smashed in there to prevent loosening.
I ended up with the Golf rack as a bit of a punt from eBay at £25 delivered. I'd read that the ball joint distance was about 550mm (chassis could be tweaked to compensate for that), but it turned out to be somewhere around 570-590mm due to the tie rods being adjustable and locked off with a lockring, result.
The downside is that it only offers 36mm per turn... but I could chop the steering arms down to 80mm from 106mm to give 24deg of front wheel movement per turn. It was also designed to run with the rack behind the front hubs (Escort and MX-5 are in front), meaning I could flip the rack over and have the column to the left (rather than to the right like Mazda and Escort), which would give better clearance to the pedals.
I decided on the Golf rack, so chopped / modified the tie rods ready to take some aluminium track rods with rod ends:
Then found out that the input spline was a stupid size (40T spline) and all the UJs were megabucks 
So I've now gone back to plan B and the Escort rack... no big deal, it will still work fine!
Thought I'd found the perfect wheels too - OZ Racing ones from a Formula student car, 13x7", 3.4kg each, forged, 4 with slicks, 4 with wets, advertised as the correct 4x100 fitment for Mazda - couldn't have envisaged a better setup all for £350!
However...
A***. Turns out they are actually something like 97-98 PCD. I've got a way around it though after some deliberation... just awaiting a 60 degree inverted dovetail cutter to arrive through the post then I can confirm it's good to go. An additional ballache I didn't really want, but worth going through for these wheels I think.
Then I also found a bargain dry sump system (£400 for the lot) and couldn't resist... so much for a budget build, lol.
But this does have a few benefits. 1) It will definitely not oil starve now, 2) the manifold clears the sump without modification (by less than 2mm), wooo:
The oil pump goes in place of the standard water pump, meaning I need a separate electric pump now... Luckily the cooling requirements of the engine aren't huge, so only needs a tiny pump - in fact the one SBD recommend for their up-to-300bhp-turbo-nutter-Busa engine is a Bosch PAD one (15L/min), which turns out to be exactly the same pump Mercedes use to cool the gearbox on an E320... You can guess which option was cheaper 
I can also mount the pump almost anywhere, also really low down, so gives more options regarding radiator position.
Need to sort out a way of controlling it now (sod paying £150 for a Craaaiiigg Daaaavid one) - have got thoughts about a heater fan resistor / switch from an MX-5 (just stick the pump on low for warm-up to keep things circulating and avoid hotspots - also as a manual controller for when back in the paddock to keep things moving around) plus a low temp (75-80 deg, ish) fan switch that kicks the pump in and out, running it at full beans when needed. Just need to get it all straight in my head...
Anyway, had a gander inside while the sump was being swapped and it is absolutely spanking in there, can definitely believe this was a ~750 mile engine:
Manifold hangs down from the sump by 75mm, so set up a 78mm tall platform and sat the engine on this in the rear part of the chassis - before I got stuck in with the welder I wanted to make sure the diff / half shafts would work and the engine cleared the chassis...
Engine is about 8-10mm away from the chassis there, and lining the sprockets up puts the diff about 11-12mm from the centreline of the chassis - result. The 1.8 half shaft was 20mm shorter than the 1.6 one, so that almost perfectly puts everything back into line again.
(Diff isn't going there, it was just to check the left-right spacing)
It was then time to grow some balls and actually do some welding. Just tacked the rear part into place for now, in case of any severe oversights. My tacking is usually ****e, about 30% on one tube and 70% on the other or something, haha, so actually concentrated this time and it came out ok.
Then re-situated the rear part to give space for the front part to get built up. Also chucked the seat in to give an idea of perspective. Yes, that is a high roll hoop, yes I did typo the dimension when I sent the drawing off, lol.
Never mind, there's a couple of benefits from it being taller than planned, and at least it means even giants will be able to drive it, haha.
Next up - more chassis work, then once the main outline for that is done I can move onto making wishbone jigs.
Cheers!
Adam
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