Locost Build diary 2005

It's Jan 2005. I've done some work on the car: basically trying to finish the chassis so it can be painted and brought to my home. To do this I have to try to finalise all welded bracketry & this involves actually designing some of the bits to be held by the aforesaid brackets. So I've been working on pedals, reverse/handbrake, roll bar tank and scuttle. I'll also have to buy some seats so I can stick the brackets on for them.

Anyway one thing at a time: I've started work on the reverse/handbrake thing. Here's a solid model

You can see it has a wilwood mechanical spot caliper handbrake and a fwd cavalier starter motor to provide rearward mpetus.Here are some stages in the production of the wilwood mechanical spot caliper bracket. Yep that's a coke fired forge...

Here's a snap of the finished main plate complete with caliper bracket, caliper and starter motor.

I've sourced materials for flanges and a thing to go over the gearbox output cog to bolt the short front prop onto.

March 2005

Still aiming to finish the chassis; I've installed brackets for the handbrake and the steering column (still have the plummer block to install for the front bearing). I've made the shorter front propshaft out of a shortened honda CRX prop - it's very small and neat; made the cog prop flange adapter (M8 fine bolts to prop and to hold it on) and turned up my sierra rotoflex coupling components to integrate onto a shortened sierra rear prop. I only have the taper to put on the intermediate shaft in the reverse/handbrake thing and a big stainless gear to find for that & it's all finished.

Things to do: 

Order seats; put fixings onto chassis

fit fixing brackets for handbrake bellcrank

fit fixing brackets for steering column front bearing

fit seatbelt mountings

order and fit roll hoop

Photos of propshaft adapter assembled onto the R! output cog and the nice little front propshaft.

May 2005

Well it's nearly summer, we've had some fine weather, the bluebells are out & I've done quite a bit on the car (were you expecting that?). It's funny how the first 2 days work on the chassis impresses folk - they think I've done nothing in the year since....

Where to start - OK CAD I made some pedals out of lumps of scrap steel. Then drilled big holes in them to lose a bit of weight. Then I used the FEA in solidworks (COSMOSexpress) to check the strength. What a cool piece of software that is. Turns out I need to add a fillet to get strength over 1500N push on the brake pedal. I've also built up more of the reverse/handbrake thing; the shaft is done, tapered, keyway in. I found some nice 10mm ID void bushes to mount it & these are welded to the chassis. The big gear, I've decided to laser cut this from an autocad (dwg) file - there's a local firm in the business. It seems 10mm stainless is a bit thick for their laser but they can water jet it. It will be interesting to see if the finish is good enough to work well as a cog - they reckoned 0.2mm accuracy. It will make an unholy racket when reversing anyway....They reckoned 30 to 50 quid - bargain if you ask me!

Pedals are done & pedal mountings welded to chassis. Steering wheel support welded to chassis. I've just realised I've dropped a bit of a clanger in that I'm set up for a metro master cylinder on the brake - this sticks vertically up - right where the steering column has to go - DOH! may have to do some re-engineering there.

Bought a roll- over bar from MK for 45notes - looks lovely, now welded in place.

Bought a nissan micra rad for £15 from the scrapper (off a G reg micra) It's nice and small &I've welded brackets onto the chassis to hold it. Both in/out pipes point straight at chassis rails - I'll need a rubber hose "chicanes" for each!

Jobs left on chassis are 1) rear stays for roll hoop and 2) upper seatbelt mounts then it can be painted and transported here for panelling/bodywork/assembly. Sorry - no new pics - I'll remember to take the camera one of these days!

Now 22 May; congleton laser have given up trying to get the big gear cut, so it's plan B... make a 8" blank and get it gear cut by my sister in law's brother - hopefully for a few beers. This will be a much better job at the end of the day - fingers crossed!

Today I finished spraying the complete (hurrah!) chassis with zinc phosphate red oxide primer & brought it home to knutsford on my roof rack - here's a photo. The bad news is there was NO WAY to get it round the back of the house so it's always going to be awkward to work on & have to live under a tarp - but hopefully it's not for long, just until I get the aluminium skin bits on then it's away to be painted properly - (all light green). I now have to find a source of aluminium sheet. Anyway - with the chassis here I should burn somewhat less diesel!

chassis at the side of the house - looking pretty cool now it's painted!

Completed reverse/handbrake module - only missing the big gear... looking damn fine!

Found an ally sheet supplier in crewe (Houston's) who have a good stock of scrap Al sheet - job for the weekend....

July 2005

Been busy - the scrapyard said they had the sheet I wanted but were lying, big waste of time, petrol etc - so I ordered some new. Got 1.5mm for the flat sheets, ended up buying 1055 which is not the best for the purpose but it'll do. For the sides I'm going to use thinner material 1 or 1.2mm & get the 6016 (or was it 6061).

I've attached the sheets with 3M VHB tape: this stuff sticks like crazy when you get the surface prep right. Here's what I found: I'd painted my chassis with a coat of zinc phosphate primer as it's living outside for a few weeks...

1) Chassis, scrape the worst of the primer off with a file or chisel, then use a flap wheel in the grinder for the last "polish". A good wipe with the IPA/water cleaning stuff & you're ready to put the tape on. If you try to use a flap wheel to take off all the paint it ends up smearing it instead & you'll grind through the tube before getting a nice surface!

2) Ally sheet. give the bits that will be stuck a good rub with a DRY panscrub (scotchbrite type thing). Then a rinse with the IPA mix & kitchen roll pulls off the ally dust leaving a surface that's dying to stick to the tape.

the cleaning stuff is 50% IPA/water mix (isopropyl alcohol)

So I'll be spending about £100 on aluminium and about £60 on tape and about £20 on sealed pop rivets (I got a box of 500 & it's nearly all gone....)

I spent £30 on 6mm rivnuts - they came in a box of 500. I'll only need a few of these so I'll flog the rest at £6 per hundred to folks on locostbuilders....

I spent £20 on a wee sheet of stainless to make my handbrake disc cog. This is 316 stainless... It is seriously hard & tough - I've drilled some holes in it & had to sharpen each drill about 3 times! It's way too hard to consider tapping it, so instead I'll thread the spacer between the gear & the prop flange, make this out of 10mm steel. it's only 201mm across so it's a bit smaller than I wanted, let's see how it goes.

I've attatched the nosecone with 2 hinges underneath & I'll probably add a couple of rivnuts on top. Oh yes the body panels arrived from GTS in a nice lurid green (I asked for opal fruits lime colour) - actually they took a long time to arrive but I wasn't held up. Slightly more of an issue they sent me a bonnet instead of a dash; They sell good kit but demand has clearly outstripped their organisational capabilities so they're going through a painful success period where instead of solving their procedural issues Darren's trying to hide from them. I'll wind them up about the dash next week I guess - the quality of the GRP bits is fine.

My target for this month is to finish the body panelling & get the shell painted - then I can start final assembly and wiring!

End of August 2005

Finally finished body panelling - could only get ally grade 6084 in the end at 1mm, but it seems like the right stuff & has gone on OK.

I've made the holes for suspension components and exhaust & "joddled" them in for strengh (& no sharp edges) so now it can go off to be painted. I feel like I'm on the downhill stretch now!

I've been looking at the brakes (I bought some wilwood dynalite single calipers ages ago). It turns out that these fit the front wheels but not the back, so I need to swap 2 for "dynalite single floaters" which (fingers crossed) WILL ft in the back wheels. I also need to make some caliper brackets for the front. Right now the plan is to use 2 off steel sheets, front and back with spacers - I should be able to make these fit easily & they should be really strong (being one each side) and easily adjustable for best fit. I'll optimise the placement using easily modifiable 2mm or 1mm sheets, then make the real things out of 3 or 4mm.

Here we go, this fits perfectly in the wheel (3mm to 4mm clearance everywhere), right first time! (there's a novelty). I'll replace the wheel side sheet with a 4mm one & bolt on with fine thread M10s. I end up needing a disc diameter of 262mm with an offset from hub flange to centre of disc of 43.5mm. The hole dimensions on the sheets are as follows (all 10mm holes): upright mounting holes are 120mm centres; caliper mounting holes are 82.5mm centres; line joining caliper hole centres is 25.44mm from line joining upright hole centres

This looks very good - I wanted minimum unsprung weight & this is looking painless, effective and "right"

End September 2005

I got the car back from the painters on Thursday, now all lovely shiny lime green, I transported it there and back on the roof rack of the pug, which seemed to survive the experience! I got the wilwood dynalite floaters too, these are going to need a seriously complex bracket making: the bracket has to locate one of the pads (I wasn't expecting that!) miss the disc and the bolts on the disc. Anyway I've measured up & it looks possible, I'll have to make one in solidworks & see how it comes out.

I spent a happy day today bolting things onto the car - wow it was like having a kit! So the diff is on and 3 sets of suspension are on (I'm saving the back left for my caliper bracket design) The rack is on (I need to make 2off 4inch rack extensions). I put the centre bearing in position and measured up the rear prop section - 28.5ins - I'll get round to congleton propshafts tomorrow. Plan now is wheels/brakes/drivetrain/steering/wiring (in about that order) to end up with a living car - I'm hoping I should be in the neighborhood of mobile before winter gets too unreasonable.

Next job is disc bells. I need to order some material (HE30 alloy) from my mate Jeff - I got a set ages ago but it's not thick enough. He's got a bridgeport vertical miller so he's in the frame for making rear caliper brackets the lucky man. I'll get some pictures of the car when it's light. I'll also write up the brakes thing separately as it all looks a bit swish. I'll save all the drawn parts as pdf files so anyone wishing to re-create just has to make the bits (just..... ha ha hah)

October 2005

Here are some photographs showing the paint job and the work I've started on the brakes.

On the brakes I've turned the disc bells and now I've also machined the rear caliper brackets. I got discs, front ones 268mm diam x 10mm are rear discs off a ford galaxy (I think - I'll check that) and the rear ones 252mm diam x 9mm are front discs off a 1970s skoda estelle (class). I've bought 1/4" NAS bolts and 12point 'k' nuts to bolt disc to bell. I got the rear prop made - to discover it was 1/4" too long: the donut bolt heads fouled on the centre bearing support bracket. So I parted it off & re-welded. This week I'll get the steel brake parts zinc plate/gold passivated and finish machining the disc rotors - had some difficulty there due to my lathe not really being big enough for 11" diameter work... But I managed!

November

Still working on the brakes: the steel's back (looks lovely in zinc & gold) & the bells are finally machined, I'll send them off for hard anodising this week. The disc rotors are done. I've made the bronze bushes for the pedals to swing from & a nice 16mm steel bar for the bushes to pivot on. So the other thing to do this week is to buy a length of kunifer & pipe up the brakes: better source some flexis while I'm at it. I've made some nice track rod extensions out of some 19mm hex bar (though I think I'll shorten them to 4 inches) and have checked the bump steer - looks pretty good actually, there's room for a minor adjustment on one side. Just for interest I weighed the unsprung weight front & rear with Martyn's bathroom scales. It's 25kg front and 31 kg rear. The front will go up when the cycle wing goes on. Here are a couple of pictures of the brakes trial assembled.

OK it's the end of Nov. and the brakes are done. The disc bells are hard anodised & the discs bolted up, all pipes, flexis and master cylinder, brake light switch and proportionaing valve all bolted up. The brakes were bled this morning & now I've got a lovely firm pedal after about 1/2" movement. I tried it being pushed round the close & the weighting feels perfect. I'm very pleased (there was plenty could have gone wrong.....). Finished brake pictures are above.

Brakes design files

OK I know I said I'd write up the brakes thing separately, but there doesn't seem much point. Here are some pdf's of the parts I fabricated to make the system more 'sevenish'. You may well believe the modifications aren't worth the effort - fair enough, it's just a few pounds of unsprung weight. I actually like the look of them - the stock mx5 rotors are only 9" and that looks a bit weedy even in a 14" wheel. This design puts 10.5" rotors at the front and 10" at the back, the alloy bells look very posh and the wilwood calipers cap it all off nicely. The calipers are "dynalite single" at the front and "dynalite single floater" for the rear. With the wheels off it all looks very formula 1 - shame no-one ever sees it thus! The fabricated parts are

1) rear caliper brackets - milled from billet steel  files/rrcalipbrack - Sheet1.pdf

2) front caliper brackets - cut from 4mm steel plate. Note the "inside" plate on each side will be remade from 3mm steel plate and extended to form the "trailing" cycle wing support bracket

3) disc bells - turned from HE30 aluminium alloy and hard anodised  files/rrbell - Sheet1.pdf   files/frbell - Sheet1.pdf

4) disc rotors - modified standard "spare part" solid discs: Ford galaxy rear discs (front) and skoda estelle front discs (rear) files/frdisc - Sheet1.pdf    files/rrdisc - Sheet1.pdf

Rotors and bells are bolted together with 6 1/4" diam NAS bolts and k-nuts (got 'em from N Skidmore on racecar)

Caliper mounting bolts tend to foul the disc/bell bolts so these M10x1.25 bolts were countersunk in the lathe & sat in a countersunk hole on the brackets. Rotor can be centralised in the caliper if necessary by placing shim washers on the caliper brackets. Mine fit nicely with the dimensions above. Here is a link to a spreadsheet where I checked on the balance and proportioning valve characteristics - it basically compares the weight on each axle compared to the braking force on each axle at various deceleration rates. As long as the fronts have more force/weight than the rears the car won't do an unscheduled handbrake turn when all you want to do is slow down. Note that a prop valve does a better job than a balance bar on changing surfaces - it allows the rears to do more work on a slippery surface and should gain at least 10% better retardation on a bad surface, compared to a balance bar. If you ask me that's where 10% better retardation might be very welcome!

If you go this route you'll have to engineer a separate handbrake, e.g. a transmission brake on the prop. Unless you have a lathe and access to a miller the engineering costs will be exhorbitant. Even with these you're looking at a couple or 3 days work. Materials and finishing (hard anodising, zinc & gold) cost me £130, the discs £70 and the calipers £230. Or you could just stick with the mx5 brakes..... Note if you have 15" rims or bigger, the "2000 sport" mx5 model has 11" rotors & the upgrade kit comes with caliper brackets and rotors for the rear. At the front 1.6 (small) brakes can be upgraded by changing the brackets for the later 1.8 ones & swapping the calipers left/right & fitting the bigger rotors. In other words there are many mx5 brake upgrade paths available - what I've done here is to try to engineer an ideal "seven" system onto the mx5 uprights. It's a 1/2 weight car so it doesn't need the vented discs. Lower CofG & more rearward weight bias. More power but less weight. Have I got it right? I dunno yet. They feel right and look right & I'm pretty confident they will be excellent.

December: 4 Wheel Alignment

I had some wheel alignment setting up to do & today was the day. This is just establishing a baseline setting. I used a spirit level and a laser pointer (actually my spirit level has a laser pointer built in . . . . ) I set up the car horizontal on its trestles and set the camber to zero on full droop on all 4 wheels using the spirit level again. This will give slight negative camber at ride height so it seems like a nice easy repeatable starting point. Rear toe was set to zero as well (also zero 'crab') using the laser pointer on a pre-defined point on the front brake calipers! Front toe was set to zero and identical "amount of thread used on the track rod" on each side, finally the laser pointer was used to check bump steer by shining it at my sensible car which was parked about 20ft away. This revealed the need for a 0.5mm shim under the left rack mount. Done! That was really easy! It showed up a huge advantage of the way I'd engineered the rose joints on the rear lower wishbones: I was able to A) adjust these by less than 1/4 turn to get everything spot on B) without any dismantling - neither of these are possible if you use the normal system where the rose joint is screwed into a bung in the end of the wishbone tube. "I love it when a plan comes together" - Hannibal Smith