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.
So, I now have 5 different tins of chemicals that I use for composites, and some aluminium racking on which they sit. Needless to say, it’s a minor faff getting to the tin at the back when there’s plenty of other stuff on the shelf. To fix this, I bought some drawer runners, some 150mm wide MDF and set about making a custom shelf (I 3d printed the mounting brackets and the tin holders). I had printed some tin holders so the tins won’t wobble over – everyone deserves a chance to be a Weeble.
However, I was bonding them in and I nudged one and I didn’t notice. It’s slightly wonky.
I don’t know about you, but I can’t leave it like that. There’s a new part coming off the printer now (5 hours print) so I can replace the wonky one and square it off.
The questionable moral about this sorry tale? I’ve seen a few race-cars up on the ramp at my friend’s garage, and they look great from above. It’s when you get underneath them do you see if someone really cares. Are things routed neatly, is that a nice weld, or a bird-shit ‘good enough’ weld because no-one will see it. (before you ask, bird-shit welding is never good enough. Some people think it is). Have people taken the difficult but ultimately better route, or just clagged it in?
It’s even worse for kit cars – it needs to be neat – I’d never be a passenger in a car that looked lashed up.
And for the detail obsessed among us, they are soft-close drawer runners. Of course they are. Sheesh, what kind of animal do you take me for?
So, the first engine mount is now nearly a mould. I thought I’d share the prep process I’ve been going through in taking a 3D printed part to a CF part.
There are elements of the printing process I’ve had to compensate for – mainly that a part is many thin layers of plastic. For a non cosmetic part, this doesn’t matter on the the top of the part, but it does on the side. The gel-coat will go into the very fine layer lines there and lock the part. Also I made the part in a few sections and they had a visible seam where they bonded together. I had made it in sections for a couple of reasons – firstly because I only have a bed of a certain size. Secondly making it in a modular fashion means I can correct a small part of it, rather than waiting 10+ hours for a full print. Saying that, what you gain in flexibility you lose in post-prep time.
The post-prep phase is summarised as fill, flat, and flange.
So, I used some Dolphin-Glaze liquid filler to take care of the most obvious demands (such as the seams):
Once I’d got the filler in, I did some rough flatting. I also made a mistake here that can just be seen on the red piece on the side. I made the parts with a biscuit cut on each mating surface, and used printed biscuits to help lock it in whilst I bonded it with 2-part fast setting epoxy. On the red part at the mating surface it curled up a little. This wouldn’t have happened if I’d clamped it to the bench when the glue was setting. No biggie – when I flanged it later, I clamped it and bonded some carbon to the back to stiffen it and hold it in place.
After this I sprayed it with high-build primer and briefly flatted it. I used a rattle can rather than mixing up some two-part just because it’s a pain to spray. I have the correct mask and so on, but it’s just a lot easier for a small part to use a rattle can, even if it’s not the cheapest.
So – one flatted 3D printed complex part to make an engine mount.