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.
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.
I’ve created the front engine mount in CAD (another post to follow) and now I need to test the engine height with the mount and the bonnet fitting – it’s no good having a beautiful mount if the engine then doesn’t clear the bonnet. I’ve gone for a trial fit of the mount (several hours of CAD and printing) to be sure it works before I go through the process of moulding and making the CF part. What I wanted to do was put the mount in place (it cradles under the front of the sump and bolts on to the front of the dry-sump). It also needs to curve around the awkward external dry-sump pump which seems to get in the way of everything.
Having fitted it, here are a set of photos that attempt to show the bonnet in place, and the engine having about 30mm of clearance between the top of the engine and the bonnet. One of the other interesting things about doing this is it’s the first time in a couple of years that the car has had any bodywork attached. It’s gone (in my head) from an abstract chassis concept back to something that relates to being a car again.
From a reference point of view, the sump will sit between 115 and 125 mm from the floor, and my suspension is height adjustable so on a track I can lower it a bit more. Right now, I’m safe to go over a house-brick without writing off the engine.
Here you can see the bonnet resting on a clamped large table-mat as a reference line. (Clamped to the top chassis rail). The mat and clamps weren’t strong enough to handle the weight of the bonnet, so I needed another idea. So, what you can see sticking down is a piece of (cut to size) wood that represents the chassis rail height to the floor as a relative position. The table mat is now just sat there without any vertical load – it works well as a reference point.
With the bonnet properly propped, this a bit of a scrappy shot down the bonnet. There’s loads of clearance here, and you can see the CF footwell and gearbox.
More of the same here and you can make out the 3d printed blanking plates I made.
And again – hopefully you can see the oil filler cap at the front a good 30mm below the bonnet.
Here it is from the top down. It looks a tiny bit like a car again.
So, Degassing is the process of getting all the air out of the mixed resin. This leads to stronger parts with a better cosmetic finish – you aren’t fighting tiny bubbles that appear in the resin, or that start to appear as the resin warms through the exotherm and the gas expands.
It’s simple to do – you put the resin in a chamber – evacuate it and watch the resin bubble up as the air comes out. As the bubbles near the surface, you let a little air in to equalise the pressure, the bubbles subside and you continue until under full vacuum, no bubbles appear.
However, it’s NOT SIMPLE TO DO: I lied. There are subtleties to this, and if you just open the tap carelessly,it’s easy to let the air in too fast and get resin everywhere. Also, you end up shooting air into the resin you were trying to clear of the damn stuff. This is also how you trash a degassing chamber, and they aren’t cheap.
The following youtube video I made illustrates this with water. Read on to see how I fixed this with a simple 3D Printed part.
So, I designed and printed a part that moved the air and vacuum over to where it was needed:
So, using some gum-tape to fix the air-guide in place, I now have a degassing chamber that lets air in without worrying about shooting it back into the resin.
So, after scrapping my first CF tub, I decided I needed to improve a lot of things (thanks Vic) before I should commit lots of materials for the next tub. First of all was to improve my vacuum management.
What I wanted to achieve was:
Firstly, I created a vacuum manifold, printed a bracket and mounted it on to the side of the compressor. The manifold is actually a gas manifold for a caravan gas supply, and I got it new from Ebay for about £30. The manifold itself actually has a non-return valve in each tap assembly, so I had to fettle that. Not a hard job and subject to a different post.
Next I mounted the catch-pot onto the vacuum tank (or an old compressor I repurposed). This was relatively painless – again I printed a bracket. This time it’s the orange thing under the catch-pot. All it is is something that is curved to the tank on one side, and level on the other. Thus I could mount the catch-pot on the level. I bonded it onto the tank with metal-epoxy, and used double-sided tape to stick the pot to the mount. The tape is monster tape – it’s fearsome stuff won’t let go easily. It will let go if I need it to.
Finally the whole thing was piped up (below) and tested.
Once I had this working, I decided I wanted another bench manifold, and made one out of push-to-fit pneumatic connectors. This means I can put my degassing chamber on the bench and not have to connect it directly to the vacuum pump. There’s little time between degassing and infusing, especially if you have 3kg of resin in a bucket – it’ll start exotherming quite quickly. With my manifold setup, i can hold the part under vacuum whist at the same time degassing the resin. Then I just need to connect the feed line to it and I can go.
What you can see here is one branch of the manifold. There’s a t-piece at the bottom, and a valve in the middle. The top is the output. Again, I printed some brackets to give me just the mounting I wanted, and the white bracket in the middle is actually a 15mm hinge-clip for attaching standard poly-pipe when plumbing. They’re £6 for 100, so I bought 100. I have many spares. The top blue bit is the outlet at this part of the manifold. It lets me plug an 8mm pipe straight in to the quick-release connector.
This is the final manifold – the picture isn’t great, but you can see three outlets. It’s set on an old tool-board I used which I didn’t need anymore – far better reuse that (considering it was already bonded to the wall).
This is a vacuum exhaust fitting. I’ve designed it to be deliberately flat so the release film will stretch around it. I’ve previously used these silicone connectors from easy composites. They’re quite good and just over 3 pounds each. The connector I’ve printed has a hole for a 6mm hose and a stop at the bottom so the hose just doesn’t sit on the mesh. They also have a larger surface area sat on the mesh to help pull vacuum out. Mine aren’t reusable, and only cost 19p each to print, and take about 15 minutes.
I did a large infusion for the tub recently, and had no end of problems, to the point of scrapping the tub. I’ll write that up later, but one of the issues was that one of my pipes jumped off the clamp and sucked air in. Rather than use a simple OTS clamp, I’ve printed something specific for a 10mm hose and a 10L bucket. The hose is a snug fit and the height from the bottom of the bucket can be nicely set and held just with friction. No more springing hoses ever again.
Or ram pipes, or velocity stacks – whatever.
I’ve made these trial pieces. The plan is to have a veritably huge amount of length variations, so when I set my engine up on the rolling road, I can mix and match to get just the variances in length I need. When I say I, I mean Damien from Daytuner, but you know what I mean.
I love it when you ring someone for a bit of advice and you get an answer you totally didn’t expect.
I’ve finished the engine build, and am about to sort the chassis mould, which means I’m not far from a rolling chassis. I’m gathering together some of the engine components I need and wanted to be sure I had the right advice on intake trumpet lengths I called Damien at Day Tuner – it makes sense to try and get this right before getting to the rollers.
Then Damien came up with the best idea: to quote “with your facilities, don’t try and guess the trumpet lengths, or go from rule-of-thumb. Print out lots of trumpets and we can chop and change over the day”. Bearing in mind pressure waves under the bonnet, you may actually want a selection of different lengths.
To the 3D PRINTER MINES !!!
