So, after the first couple of attempts at making the exhaust, I realised I was designing and printing myself into a corner, so I decided not to print anything else until I had a full design I trusted, to the dimensions I wanted, and this is it … this is version 6 of the design.
I’m pleased with it because the worst deviation from spec is pipe 2, at 1.5mm. Pipes 1,3 and 4 are all within 0.5mm of their proscribed length. Length is defined as the distance the gas has to travel rather than the amount of pipe needed to implement that. As such, all my lengths for the bends are taken from the centre-line radius, rather than the amount of pipe needed to make the bend.
By good luck rather than good judgement, each pipe seems to follow on a theme from the other pipes, and they look like they’re meant sensible runs, rather than all sorts of convoluted bends and wiggles. Furthermore, all the bends are from Alunox stock bends, and I’ve managed to keep to the largest radius for smoothest flow.
It has created a slight issue though, in that the yellow pipe fouls the steering column. I can fix that by slightly changing the route of the column, and maybe adding an extra UJ.
So, I’ve completed the first 3-D printed prototype exhaust pipe. Every straight and bend is taken from an off-the-shelf exhaust part supplied by Alunox. This means if the 3-D printed parts fit then the exhaust as I make it should fit just as well.
I like my analogue dashboard, and am very tempted to keep it when I retire. However, getting access to it has always been a pain. Furthermore, the interior of the engine bay from all the mods made previously was starting to get a little tatty, so I’ve solved two birds with one stone. Below, you can see many holes for things like fuse-banks, heater access etc. There is no heater anymore, and fuses/relays will be replaced with solid state relays (SSRs).
And here we are part of the way through. I’ve trial fitted the panel and fully fitted the rivnuts as fasteners. The plan is the panel can be removed from the engine bay in a minute or two and then full access can be had to the back of the dash. Not every rivnut went in easily – some had to fit over what was an open hole and required small support pieces. However, the plan was always blind-ending fasteners.
Here it is from the back – a much better approach (I think) and you can see the black patch-panels I had to bond in to support the fastener.
Finally below is the finished article. Tidies it up quite well. Added a little weight but I can live with that for the convenience bought. The bottom panel is fully bonded in – I couldn’t see any advantage to making it demountable. The panel to the right with the gaping hole is also going to be relieved and replaced – similar on the left.
So, the parts to the exhaust are going together nicely. The plan is to make a mockup of parts I can buy off the shelf, make some clip-together parts to simulate the bends I need, and then buy the parts and build the exhaust. This means I don’t need to cut any expensive stainless until I’ve got the design and the jig completely right for the exhaust.
So, a few things have moved forward. Bailey and Morris shipped me a lovely prop, and now I’m making a suite of aramid prop catchers for it. The plan is the catchers are printed, moulds taken from them, and then then made in Aramid. They should be light, and easily able to handle the abrasive loads.
The mount is in, trimmed and holds the weight well. It also has been cured, so there should be no issue with the heat from the engine softening the resin. I am having some custom fasteners made to secure the mount to the aramid chassis – similar to these but to my own dimensions and specification of metal. I can then hard mount the engine mount to the chassis. I’ll also need to make a torque-control bar that attaches to the engine and stops it yawing when it spins up.
The mount now bolts nicely to the dry-sump. It’s actually quite a complex part, made in multiple separate stages:
print the part, make the mould, lay and infuse the part. I’ve already written a lot about this, and you can get to it via the ‘engine mount’ tag.
make the cross-bar. This needs to be very strong in compression and accommodate the hard points of the engine Bolting through it. To do this, I made a 5mm thick sheet of woven glass, infused with hig-temp epoxy. I chose glass because it’s strong in compression, and of course a good insulator: there is no galvanic response issue to be had which would happen if I made the plate out of carbon.
I then made a jig from the front of the dry-sump to capture the wiggly up and down bit and the bolt holes. From the Jig I transferred this to the glass fibre plate, cut and fettled until the plate fitted the sump-front nicely.
Next came the problem of attaching the plate to the cross-member. I had a plan … successful, as it turned out. I bolted the plate up, and lowered the engine down to the mount, onto a bed of the easy-composites two-part structural adhesive. This accurately located the plate on the cross-member. I let that set. All this would give me is accurate location. I couldn’t trust the adhesive to hold the plate in place in the rigours of the engine bay.
Once set, I extracted the mount, and set about fixing it in place for good. I created some 45 degree chamfered foam corners to act as an interface between the plate and the cross member, meaning not only would the cloth not have to go around any extreme angles, but it would also gain some strength in a rocking front-and-back motion.
Once the fillets were in place (a smidge of hot-glue), I then layered CF between the cross-member and the plate (3 layers of 300 either side) and then one layer of woven glass on the outside of each side. Again, I’m using glass as an insulator between the bold heads and the CF – it’s easy to work around galvanic response issues, so why not do it?
Finally, I bagged it in a tube-bag and infused high-temp epoxy over it again. Then a curing cycle in the domestic oven and viola: an engine mount.
There’s still stuff to do though.
Firstly, the bid coloured in red on the mount needs to go – it is too tight against the left chassis rails. Once gone, I have more room to finally position the engine before I bolt it down. To bolt it down into the floor pan and I have to make some hard points for that. Watch this space. I have a tested technique which I’ll share next.
Firstly, to quote Granny Weatherwax, “I aren’t dead”. I’ve taken a swerve into making my daughter a carbon-fibre violin case for her rather nice violin so the car stuff has been paused. The case is a heavy bugger, with four layers of carbon, two layers of aramid and a 5mm core in. What it is though, is proof against a claw hammer, as hard as I can smack it. Repeatedly. Over an egg. For a professional musician, lightness is very much secondary to protection, say from being left near a car and driven over, or dropped. When a quality instrument can cost thousands, weight becomes less of an issue.
Now, to my quote above. Nick from Project Binky believes that the way into heaven is to have the most tools. I agree with him. One of the things I’ve found making the case and working with CF is that the best way to cut it is with a diamond tipped blade, and I went looking for something that did the job well. I found the Exact Saw. Not only would this tool get you into heaven and cut angels, it would allow you to also cut a path down so you could party in hell when you fancied it.
I watched a couple of the advertising videos and thought … meh -“If it’s half as good as you are making it out to be, I’ll be impressed”. Pish and tosh. it’s all that and more. Hook it up to a vacuum and plunge away. It’s really safe – it would take a conscious act of idiocy to get your fingers near the blade. Mine came with about 20 cutting disks of various nefarious purposes and it chews through anything I put in front of it. As an example, I was cutting 19mm particle board at the weekend. Admittedly I only have a 12mm plunge (on the saw, missus, on the saw) but I did a cut from either side. It flew through the wood, was far less stressful and much straighter than a jig-saw, and far-far safer and less terrifying than a rotary blade saw thing.
So buy one – cut your way into heaven, gut an angel.