Half Finished
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| posted on 1/9/18 at 12:09 PM |
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Haynes Roadster MX-5 scratch build
Hello everyone, I have been working on this for a while now. I thought I would share my progress so far.
This will use as much of the donor car as possible to keep the budget low. I am planning to use a Speeduino ECU. I am hoping to make/fabricate as much
as possible of everything else. I am using the Saturn chassis plans.
I managed to pick up this sorry looking donor car as an MOT failure for practically nothing. I stripped it down for everything I needed and sold
everything else. I managed to make enough money to buy the box section for the chassis later on.
 
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I weighed in the battery and picked up some scrap box section steel for my build table.
 
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The legs are bolted on with coach bolts. I'm hoping to store it if I decide to build a second one later on.
The top surface is just 6 pieces of chip board fixed with sheet metal screws. The build table is made from all scrap and cost me nothing in materials.
 
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After marking out the chassis dimensions I cut the base rails to length with an evolution chop saw. It makes a nice cut and needs minimal deburring
with a file.
 
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Laying out the base rails and securing with wooden blocks.
 
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Jig for the front frame
 
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Front frame welded
 
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Front uprights in place. I know the driver side upright rail is in the wrong place. I moved it later on.
 
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Rest of the uprights in place
 
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Seat back rails in place
 
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Cutting the transmission tunnel rails. Some of these had angles on both sides, I clamped them into the chop saw with an angle to the base.
 
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Setting out the transmission tunnel
 
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And this is my progress up to today. I've been away all summer and annoyingly the chassis has a light coating of surface rust.
 
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Getting there slowly. The next step is to fully weld the chassis and cut the bars for the rear.
It is handy there is metal scrapyard next door that always has a big stockpile of aluminium and steel too.
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ianhurley20
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| posted on 1/9/18 at 12:38 PM |
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Welcome to the group . Great progress. The light rust can often be cured with a dab of phosphoric acid which converts the rust to a black phosphate.
Costs about £8 for a bottle from ebay. I used the wiring loom and ecu from the MX5 with mine and also used brake pedals and steering column as well so
all the column switches etc.
Good luck and feel free to ask questions, someone will know the answer
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Half Finished
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| posted on 1/9/18 at 12:59 PM |
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Thank you. I will get some of that.
I didn't think of pedals, I'm not sure I kept them.
I stripped the car down ages ago before moving. The bits have been sat in a shed. It should be interesting to refurbish everything, the MX5 was on
180,000 miles!
The cost of a brake seal kit is almost as much as a whole refurbished caliper.
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Slimy38
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| posted on 1/9/18 at 01:21 PM |
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quote:
Originally posted by Half Finished
The cost of a brake seal kit is almost as much as a whole refurbished caliper.
I got my seals from Brakes International on Ebay, it cost me £15 for the rears, £14 for the fronts and another fiver for new brake nipples. The
pistons were salvageable as were the handbrake mechanisms (once they'd sat in rust remover to get them open in the first place!!).
It was surprisingly satisfying to clean and recondition them myself though, I now have these waiting to go on the car;
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Half Finished
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| posted on 1/9/18 at 03:35 PM |
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They look really smart. I'll have a go with my calipers.
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Half Finished
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| posted on 12/4/20 at 08:57 PM |
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How long ago did I start this thread?! I have been making some progress again on this.
Cut the brackets from box section offcuts
 
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Started adding the rear bars. got this part jigged up and fully welded.
 
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Adding the wider section to accommodate the MX5 diff from the Saturn plans.
 
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More plates added.
 
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For the rear panel supports I made up a former. Clamped everything down and bent the two ends round with a bar.
Worked a treat. Even got the wife to help.
 
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And tacked in. The saturn plans don't have these but I'm going with the the aluminium bodywork.
 
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Even got my son helping out
 
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Next job wishbones. Parts arrived from thelatheman on ebay.
 
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I've also been looking at the best way to mount the diff. I will make up a nose mount bracket and polybush the top mounts.
I was sorting through the donor parts. It seems my drive shafts are properly stuck in the hubs. they are currently sitting up right with penetrating
oil in the cup, hopefully they free up.
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Half Finished
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| posted on 13/4/20 at 09:33 AM |
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Engine height
What clearance is best for the sump on these? Im using the MK2 1.8. I would prefer to not have the sump below the chassis rails.
Can I shorten the sump to the same height as the gearbox bellhousing and mount level?
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ianhurley20
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| posted on 13/4/20 at 10:56 AM |
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I didn't shorten the sump on mine and ended up with 90mm clearance under the sump and 5 mm clearance under the Equinox bonnet. If yours is a
VVTI engine I guess a bit of a bulge will be needed.
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Half Finished
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| posted on 25/4/20 at 05:54 PM |
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Got a bit more done on this today. Welded up the rear section and grinded down the top plates.
 
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Still need to weld the underside but happy with how this turned out.
 
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Tacked in the lower brackets
 
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and the top brackets
 
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And then welded both sides
 
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Making up a nose bracket for the diff is on the to-do-list. just waiting for poly bushes to arrive for the diff top mounts.
Bracket will bolt to top and bottom of diff and CP10/SB4
 
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I also had a chance to clean up and separate the donor parts. The brakes are definitely much newer than the rest of the car.
The rubber seals on them are actually OK. but one bleed nipple did snap off, I managed to weld on a nut and get it out.
Tomorrow's job is adding the front wishbone brackets.
I still need to make up the wishbones, I cut all of the wishbone plates from 5mm plate already.
I have all of the parts I need to get it rolling now, just as well because I lose the garage on the 5th May!
Does anyone want the build table?
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Half Finished
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| posted on 20/2/21 at 07:39 PM |
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So I moved and lost my garage since the last update. Everything has been sitting in a damp lockup since..
Recently got myself a new space with a 2 post lifter.
 
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More to follow.
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ianhurley20
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| posted on 20/2/21 at 09:36 PM |
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Now I'm jealous
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Half Finished
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| posted on 1/5/23 at 08:08 AM |
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I recently picked this back up after being occupied with other projects. I had a check list of items to finish before paint that took ages.
I can see why so many of these projects ended up on eBay as unfinished projects..
Column supports
 
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Getting the engine aligned, I adjusted the bottom of the bellhousing to be level with the bottom chassis rails
 
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Gearbox support was tricky, there isn't any space above the gearbox. so the rubber bush slots in from the front.
 
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Engine mounts made up
 
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Seat supports and handbrake supports. The handbrake is a Sierra part offset to the side. I made up an adjustable link to go with the MX5 handbrake
cables.
 
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Polo rad supports
 
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MX5 Column supports, with a small amount of adjustability.
 
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For the side supports I don't have a roll bender, this worked to form the steel bar around the side support plate.
 
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Side supports finished
 
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With the chassis finally finished I started prepping it for paint.
 
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Tools you wish you bought sooner...
 
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Before
 
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After.
I'm using POR15. This is after using the cleaner degreaser and then their metal etch.
 
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And after first coat of paint
 
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And second coat
 
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Next time, I'll just buy one.
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Slimy38
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| posted on 1/5/23 at 08:16 AM |
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Good progress, well done! Did you check the steering column for the sufficient angle deflection? Mine is pretty much the same as yours and it ended up
perfectly in line, I had to move the middle bracket outwards to get more of an angle. It also has the added benefit of clearing the engine a little
more.
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JoelP
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| posted on 1/5/23 at 08:34 AM |
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Thanks for sharing, I enjoyed reading that.
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Half Finished
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| posted on 1/5/23 at 08:34 AM |
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I have some adjustment in the column left to right in the bottom mount.
If it's inline with the driver it's under 10 degrees, But it can be offset to meet the 10 degrees.
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James
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| posted on 3/5/23 at 11:45 AM |
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Great project.
Following with interest and great nostalgia!
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"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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Slimy38
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| posted on 3/5/23 at 03:02 PM |
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quote:
Originally posted by Half Finished
I have some adjustment in the column left to right in the bottom mount.
If it's inline with the driver it's under 10 degrees, But it can be offset to meet the 10 degrees.
Aye, that's pretty much what I found when I set everything up the first time, I didn't have adjustment in mine though. I had to be a bit
more enthusiastic with the grinder and welder to get things in the right place!
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Half Finished
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| posted on 3/5/23 at 03:35 PM |
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My next issue is the rear wishbones. The saturn plans have missing dimensions and I've been trawling through old posts to try and find a
definitive answer. It seems others have ended up with excessive rear camber or adjusters wound too far out.
I really don't want to weld up a set only to find they are wrong. I'm going to reproduce the whole thing in CAD. I could even 3d print a set
of wishbones to check the fit.
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christim
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| posted on 5/5/23 at 10:56 AM |
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Great to see a build progressing! I'm not sure how many are even buying 1/2 built projects any more, seems fewer and fewer out there nowadays
My Build Thread
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Slimy38
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| posted on 5/5/23 at 01:36 PM |
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quote:
Originally posted by Half Finished
My next issue is the rear wishbones. The saturn plans have missing dimensions and I've been trawling through old posts to try and find a
definitive answer. It seems others have ended up with excessive rear camber or adjusters wound too far out.
I really don't want to weld up a set only to find they are wrong. I'm going to reproduce the whole thing in CAD. I could even 3d print a set
of wishbones to check the fit.
I hit the same and had to 'make it up'. Because I was starting with the MX5 driveshafts and diff I started with them, ensuring that at rest
the driveshafts were 'comfortable' (IE the joints weren't stretched but also wouldn't bind through the full suspension travel).
That gave me the upper and lower positions of the MX5 uprights. With the chassis mountings already defined it was just a case of 'connecting the
holes'.
I did include a level of adjustment in the upper wishbone, I think it goes from about 0 to -10?
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Half Finished
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| posted on 5/5/23 at 07:01 PM |
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Cheers Slimy38. I'm looking through old posts on here and the Haynes forum, I really can't make much sense of the measurements.
I've just made up the rear upper wishbone based on this Haynes forum post. I'm
3D printing it now so I can check the fit before I commit to welding anything.
 
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Half Finished
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| posted on 5/5/23 at 07:37 PM |
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I've also just found this amazing 3d model of the hubs. This will make things easier.
MX5 Hubs
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Slimy38
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| posted on 6/5/23 at 07:44 AM |
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quote:
Originally posted by Half Finished
Cheers Slimy38. I'm looking through old posts on here and the Haynes forum, I really can't make much sense of the measurements.
I've just made up the rear upper wishbone based on this Haynes forum post. I'm
3D printing it now so I can check the fit before I commit to welding anything.
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Nearly 11 hours for the print? Wow, that's dedication! Mind you, my 3D printer would be taking days to do the same, and that's even if the
print bed was big enough.
I just used lengths of steel and clamps to put everything in place, I'm sure wood sheets and plastic tubes got involved somewhere along the way
too.
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Half Finished
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| posted on 6/5/23 at 11:20 AM |
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So after manipulating some free CAD models. I've made this.
It's wider than the previous drawings but then then the MK2 MX5 has a 10mm wider track, which adds to the confusion a bit.
I'm starting to make up my wishbones based on this.
 
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Edited to add a version corrected for ride height and -0.5 degrees camber:
 
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This link lets you open the model in a web browser and take your own measurements:
CAD File
sources:
https://grabcad.com/library/haynes-roadster-chassis
https://grabcad.com/library/mx-5-wheel-and-tire-1
https://grabcad.com/library/miata-nb-non-sport-disc-brake-assembly-1
[Edited on 6/5/23 by Half Finished]
[Edited on 6/5/23 by Half Finished]
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Half Finished
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| posted on 5/6/23 at 08:20 PM |
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I've been making some progress on this. It's almost a rolling chassis.
Floor cut out. I've left some additional material on the inside edges for some rivnuts. I'll add a removable cover here.
 
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Cleaned up the hubs. Ready for paint
 
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Offering up the rear wishbone to check the spacing. It looks good.
In the end I adjusted my last drawing slightly to -1 degree camber, with the adjusters on the lower wishbone I've got some adjustment for the
camber.
 
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All 8 wishbones done.
 
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Next job is painting and assembly. I've got the wrong universal joint for the steering rack. My part is for a sierra but I need a group 4 /
Escort short type. Does anyone have one or want to swap? A new one seems to be £60.
[Edited on 6/5/2023 by Half Finished]
[Edited on 6/5/2023 by Half Finished]
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