Cooling

 To tick off one of the jobs, I decided to have a look at cooling. The donor radiator is just too large, I needed something half the size. The book recommends a VW Polo radiator, and going back to 1996 I can see one that would fit quite nicely. 

The problem comes from plumbing it in. The MX5 cooling system is fairly straightforward;

One loop for the radiator, one for thermostat bypass, and one for heater. The bypass one can stay where it is, the heater one will be looped back. That leaves two pipes to get from the engine to the radiator.

But then I need a reservoir connection, and this is where it gets messy. The MX5 reservoir isn't pressurised, it's cap is just a 'lid'. The coolant pressure is controlled by the radiator cap, which has a tee off to the reservoir. Therefore it only gets water into the reservoir when the pressure is too high. The fill is done through the cap. 

The Polo radiator doesn't do that, it uses a pressurised expansion tank;

The system is filled by the tank, and the tank cap is a pressure release valve. 

All of that means that if I use the Mazda reservoir, it'll end up being under pressure rather than just dealing with the overflow. The lid won't stay closed, water will go everywhere, game over. I think I need to move to an expansion tank like on the polo. But then the plumbing gets challenging, because there is no tap for an expansion tank. 

Following the Polo cooling route, the filler is connected to one of the lower pipes, and the overflow to the top. It kind of makes sense, and hopefully I can do the same. I have found these connectors as well;

https://www.carbuilder.com/uk/black-nylon-stepped-t-piece-3228mm-1512mm

Which I suspect may come in very useful. If I use a T piece to join the heater pipes, then connect the tank to those pipes, that should deal with the fill. The overflow can then connect to a higher pipe. 

What I do need to do is get to a scrapyard and find an expansion tank. Thankfully the expansion tanks were used for pretty much every VAG car so it won't be difficult to find one. I just want to find one that isn't really big and bulky. 

I'll also do a bit of Googling to see what other MX5 based Haynes have done, they must have ended up in this situation as well. 

(Edit)

Skov to the rescue again! Through my build I have frequently referenced his build, even to the point where I use the same blogger.com host. In case I lose the bookmark, here is his blog;

https://mx5-haynes-roadster.blogspot.com/

It's actually completely done, his last post was a farewell as the car got sold. So sad... :(

Anyhow, as expected he's done pretty much what I'm doing, using Polo donor parts. Here I can see pictures of the Polo expansion tank;

https://mx5-haynes-roadster.blogspot.com/2012/09/cooling-system.html

Along with clear photos of how/where it's plumbed in. He has done exactly what I am planning to do, plumb it in at the rear of the engine on the heater pipes. The only difference is that his radiator does have the extra connection back to the expansion tank. I'll need to plumb that in with a T piece off the upper radiator hose. 

To do list June 2023

 I've had a look and it had been three years since this list was first done, Covid had a lot to answer for but I'm hoping to catch up again now. So here's the list with comments;

• Finish off BR10 cut. It's just a raw end from where I had to cut it off to fit the engine, I need to smooth and cap it. Still to be capped, but as with the next one I want to go all over the chassis and finish it. Even working on the back end I found two other tubes open that need capping. 
• Other weld finishing. Just a quick sanity check once the chassis is open. To be done.
• Handbrake mount. I still want to put it under the steering wheel, I like the idea of it being hidden but I've no idea how to do it! I know where it's going and it's already been tested, it won't be under the steering wheel but it will be tucked away.
• Gas pedal mounting and linkage. Done, but....
• Clutch and brake pedal limit stops. All three pedals need limit stops in both directions.
• Seat belt reel mounting. I figured they should be mounted in the inside but they still need to meet all three points without touching the car seat. Yep, I know where it's all going so I can weld up the brackets required. 
• Radiator mount. I don't actually have a radiator yet so that might be a delayed job. Ah, I still need a radiator. Best go shopping, or at least go junkyard hunting. A quick Google suggests 310-350 tall, and 435-465 wide. I need to measure the MX5 fan cowl though, I would prefer it to match that if possible. 
• Roll cage. Still not sure what I'm doing here. 99% done. 
• Exhaust. This will be after the bodywork fitting. This will be a big job, but the engine isn't in yet.
• Oh yeah, bodywork fitting. This needs to include;
• Outriggers on the chassis. Side ones done, rear to be done.
• Mount points on the chassis. I think just the front and rear lips, but it does require curves. 
• Hinges for the front section. Yep, to be done. 
• Trimming the panels to suit. Mainly from the top of the chassis sides to the side of the body tub. I'm thinking aluminium rivetted to the tub and screwed to the chassis. 
• Painting the chassis once completed. Long way off for this one!
• Propshaft resize. I think it needs shortening, but I can't measure it without the diff and engine being in place. It does need shortening, but engine in place is needed first. 
• Fuel tank mounting brackets and straps. Strap metal is waiting in the garage to be bent into shape.
• Fuel lines. Ah yes, I need to buy a few metres.
• Scuttle panel. Interesting, I'd not really thought about this. Perhaps something to consider when the tub is in position on it's brackets.
• Windscreen (maybe? Not yet though). Nope, not for IVA. 
• Brake pipes (solid and flexi). Done and done.
• Wiring loom. OK, I've put it off for so long, but I think that is the next big job. Stripped and taped up, no idea whether it'll work though!!
• Dashboard and battery mount. That's a couple of interesting ones, again probably more for when the bodywork is in place.
• Drive it away. Yeah whatever!!

I think engine install has got to be the next big job, closely followed by the bodywork and then the front end fitting with hinges. Oh, and shopping list for lights!

Bad and good roll hoop supports

 Time for the last update from the weekend. First the bad;

This is probably the first time I've had porous welds. I did initially think gas problems, but now I've had more time I reckon it was thread cutting oil. The caps had been tapped just prior to welding, and the oil must have still been present in the seam. It's a little bit coincidental that the bubbles are roughly where the seam is, and only in particular points on the circumference.

The only thing to do is grind it all away and reweld. Which I did, and to be honest I was much happier with the penetration from the second weld. One was even good enough to keep as is, but because the other one needed tidying I thought I'd do both.

This is the final result, two capped hoop supports with their rose joints and weldable brackets ready to go. Obviously this is upside down, the brackets weld on to the hoop like this;

I'm really happy with the outcome, once they're fully welded and the bottom part is also fixed to the plate it's going to be very rigid. I guess I won't know the ultimate strength without something nasty happening, but at least this is done as well as it can be.

Last job for this then, cut the second bar and fully weld both, then brace down to the bottom of the diff cage. After that it'll be a bridge out to the bodywork at the back. 

Boot positioning

 One thing that occurred to me was that the boot lid is a separate piece, so in theory I could check it's location and see what would need to be cut. As I took it out of the shed I could clearly see it was wider than the support tubes, so at first glance it suggested I would need to cut the boot lid (or even have it non-functional). But then I went back to old photos;

This shows that the fuel tank is just short of the boot lid (actually this picture is prior to the platform being made so the boot lid and fuel tank most likely line up). So I had a go at putting the boot lid in the correct position;

It turns out that while the width is clearly enough to interfere with the support tubes, the distance rearwards is enough to ensure the support tubes are going through bodywork and not the boot. That is further confirmed by the bodywork length being 18 inches from behind the seats to the boot lid. Checking that against the positioning of the boot lid suggests it's 'about right'.

My only concern now is that the bodywork may actually line up exactly with the cross bar on the roll hoop. So instead of simply cutting a couple of notches out of the bodywork, I may have to take an entire section out. Of course, that might mean that the cross bar also serves as a terminator and a support for the rear section, then I'll just need to add some trim between the bar and the chassis. Hmm, that actually might work out better, I had been wondering what to do with that rear lip. 

Rose joint caps complete

 After a lot of welding, cutting, grinding and more welding, I finally have my rose joint caps. Two layers of 5mm steel with a welded 12mm nut on the back, giving 22mm of fully threaded end;

A quick check against M12 bolts shows everything looking good;

And here they are in place on the tubes, with the rose joint screwed in and the hoop mounting brackets ready to go (more 5mm steel);

I'm happy with the work, it all went to plan and while it probably won't pass MSUK inspection I can see enough metal at every stage to ensure that it will help if the worst happens. The next stage is to cut the bars to length and weld the fixing plates in place.

Talking of welding, I went back over the cross bar on the roll hoop and fully welded it;

Unfortunately, while I was happy with the weld itself (reasonably tidy and with good penetration), it did pull the hoop in and stopped the fixings from matching the holes. I had expected it when welding the hoop itself, so I guess it was just a delay to the inevitable. I needed to slot around 3mm into each of the eight holes to cover the shrinkage, so now the fixings have washers underneath them. It's still as strong as before, the washers are 'belt and braces' so to speak.

Now comes a little frustrating bit. I wanted to look at how the tank was going to be strapped in, compared to the support bar mounting plates. I managed to get it wrong;

The fuel tank sits on top of the plates on both sides. This means that once the tank is strapped down, those plates will not be as easy to work with. Particularly when I'm inside the boot of the car trying to wrangle the support tubes into position, I don't want to have to fight the fuel tank as well!!

Of course, it's a fairly easy fix here, I just need to trim the plates a bit. I do have the trailing edge that is already shorter, and rotating the plate showed that it would work. It's just one extra job.

I've also remembered to fully weld the bodywork mounting on the drivers side, so that's now ready to go. I think for next weekend I'm going to get hold of some Sikaflex and get the bodywork in place. So before then I need the support bars finished. 

I also want to get the straps sorted for the tank. For some reason I thought the fuel tank straps were going to be soft, turns out the book asks for 2mm steel. Of course, I don't have 2mm steel, and definitely not in the length required. B&Q have it, and while it seems to be a bit expensive it appears to be the 'normal price' for steel now. I knew I should have got this finished a while back, all these little bits are going to end up costing more than most of the chassis. The tank also needs insulating from the rest of the chassis, so I need to find a rubber strip of some kind. 

The next post will be having a look at the next jobs, or more importantly the next purchases. There's not much left now, it'll be on to engine and body work. It's looking to be a nice summer (fingers crossed) so that will make things easier to bring things out of the garage to work on. Of course, we have thunderstorms predicted for today, so just indoor stuff for now.

Rose joint install

 For the roll bar supports, the rose joint mounting is going to be crucial. It would be ideal if it was fully threaded, but I've got no way of turning a suitable insert. So I want to get as close as possible with the options I have to hand.

What I've decided on is an M12 nut, mounted on the back of a 5mm plate that will be welded just inside the tube. I will then have a second 5mm plate welded to the end of the tube. That gives me about 20mm total threaded surface, with an end plate that is double the thickness of the tube itself. The rose joint is then inserted along with a lock nut. 

The only problem with that design will be the multiple layers and how the thread will work between them. Ideally I need to weld up the three layers away from the tube, then cut the thread. That will allow me to match the thread on the nut. If I do that I'll be installing a 'top hat' into the end of the tube and only having one weld to the tube. It also means the weld between the plates will most likely need grinding away as well, again for the top hat design.

What I'd prefer to do is weld the nut to the smaller plate, cut the thread on the smaller plate, weld that into the tube, then weld the larger plate on top. But while I could cut the thread on the smaller plate, I couldn't do anything with the larger plate. 

Thinking about it, the best option would be to weld the large plate on then tap from the other side. I'll have to do a bit of work on that one to see if I can get the tap all the way through the tube, initial thoughts would be to fix the tap into a socket then use extension bars (or even a length of steel) to get the tap all the way along the tube. I might try that step first to see if it's viable. 

(later that day...)

I think I'm overcomplicating things. I screwed two spare pieces of metal on to the joint along with the bottom and top nuts. It left me with about two threads spare so I think it's perfect for the end cap. But I am going to do the whole thing off the tube first, weld all the layers together then tap straight through. As long as I get the holes in line then it'll be the strongest way of making the cap, then having only one weld to the tube will be less of an issue. 

So it'll be a fixing plate that is twice the thickness of the tube, and a total thread length twice the thickness of the joint. Then it'll need welding to the roll bar hoop, that should be pretty easy. I suspect 3mm plate will be best here, fully welded of course. 

Picture time!

 Time to post some pictures, first some useful ones. In the previous post I said I wanted to move from the bracket idea to the rose joint. This is what I'm aiming for now;

Now it does create a potential weakness in the roll bar strut, but it gives me more flexibility in the mounting. As long as I can get the rose joint securely screwed into the end of the support tube then I think it'll work (more on that later). 

Oh, one more picture from the same set;

Using string to find the route of the tube is a brilliant idea, it means that the hole starts small enough to make corrections before the bigger hole is cut. I'll be doing the same for mine. 

Now on to the show. Malvern as a showground certainly has it's advantages, not least of all it's location;

Nothing like blue skies and great scenery to really start the day off well!! 

First was the ANC Replicar, something I've seen multiple times and often turn to for inspiration. This time it was the finishing of the lower bodywork that caught my eye;

I probably won't copy it directly because I'm hoping mine will be boxed in, but it's good to see a strip of rivets used for a secure mounting.

The next photo was an idea for how to trim the boot;

This is just a fibreglass mould but it gives a nice usable finish to the boot space. I'll look at that probably after IVA?

Next was a method of boxing in the wheels. With the bodywork as it is, there is no protection at all from road debris (even a bog standard seven has wheel arches whereas I don't). This car is an example of how I'm planning to sort the arches;

Next, a bit more trim. This time behind the seats. I like the idea of plain aluminium that I'm working with at the moment, but in case it does there is always carpet. This is a pair of replicars, one with plain panels and the other with carpet;

It also shows examples of rear view mirrors (side and centre) which I will no doubt be following.

Next came this beautiful machine. It's an old version of the Healey (and it's a 100 rather than a 3000), and really gave me lots of ideas for how things will look in the end. I had a great chat with the owner who clearly had a lot of enthusiasm for his car. 

At this point I realised that I didn't have the measurements for the indicator or tail lights. While I can reuse the donor headlights, I don't have anything close to the other lights. I'll add that to the shopping list for Newark!

The one thing we did talk about was the number of sharp protrusions and corners that may have been ok at SVA (when he had it tested) but work with IVA. This car doesn't even have head restraints, and the spikes for the roof would never get past an IVA. But as with most kit cars, getting through IVA is one thing, the modifications afterwards are what makes it more like the finished product. 

He also mentioned a second one at the independent stand, and considering I didn't know these replicas existed I had to go look for it. The search didn't disappoint;

 This one had a bit more money thrown at it and you could tell, although I'll be happy if my car ends up even reasonably close to either of them. There was lots of little details on this one, like the chrome surrounds for the roll hoop. Of course the RAC badges and the rail is a nice touch, again for post-IVA.

Purely by coincidence, the next car I found was a Sebring in the same colour scheme, which made an interesting comparison;

I do like the Sebring cars, although just looking at this price tag shows they're in a different price range to what I'm dealing with. If they were still around I'd be looking at 25K to put one together. 

On the same independent stand there was another example of a car with a hinged bonnet and deflectors for road debris;

I don't recall the type of car, but as well as the flat plate deflectors under the bonnet there was also a very tidy exhaust install. The flexible joint out to the side mounted exhaust was well thought out, and the side mounted silencer looked really nice. No sign of a cat thought, which considering it was clearly an MX5 engine was quite surprising. Maybe the donor was just old enough to not need one?

The bonnet hinge here had some nice touches, like a metal wire to the engine to stop it swinging too far forward, as well as the foam tape on the body for it to sit on when closed. 

Todays progress

 After yesterdays trip to Malvern for the kit car show, I had a lot of ideas on what I want to do next. Photo's to follow, but first a progress update and thoughts on an issue.

Today I have;

1. Welded the driver side body outrigger.
2. Finished and tacked the cross bar for the roll hoop. 
3. Tacked on the rear support for the rest of the roll hoop.
4. Started to look at the brackets for the rear supports for the roll hoop. 

I'll come back to these in order, with photo's, but number 4 has left me with a problem. I got some brackets from the tube bender, on the basis that even with the slight angle I could still weld things up and get it working. Unfortunately that's not the case, even with a bit of trimming it's just not going to work. And on top of that, they are really ugly!! It's a big chunky thing with sharp points and just not what I want for a highly visible part.

However, I did see that Westfield use a rose joint as part of their roll hoop, there were quite a few of them at the show. A quick check on their page, and there it is, a 1/2 x 1/2 rose joint. It's a tidy solution, just requiring the rose joint itself on the end of the rear stay and two plates welded to the roll hoop. I already have 3mm plate so some brackets won't take long to weld up. 

But of course it's UNF, and I would prefer to stay metric. On this page there is a dimensions table https://www.mcgillmotorsport.com/1/2-x-1/2-unf-right-hand-male-xmr8-ultra-high-performance-rod-end-c-55-p-53. The 1/2 refers to the internal diameter of the hole, with the outside diameter being 1.3 inches (33mm) and the overall length being 2.4 inches (61mm). So the closest metric would be an M12 x 1.75 such as this https://www.mcgillmotorsport.com/m12-x-1.75mm-right-hand-male-xmrm12-ultra-high-performance-rod-end-c-55-p-257. Since McGill do free postage I'll get two of those.

So overall it's been a decent weekend, apart from a few more bumps and bruises. I'm not sure why but I seem to be extra clumsy lately. Hopefully it'll clear up at some point.

Right, that it's for now, I'll put a few more notes and photos during the week.