Be Precise … in all you do

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?

Engine Mount Progress

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.

3D Printed and Carbon Fibre Engine Mounts fit

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.

xmas holiday summary

Well, it’s been a decent enough holiday – I’ve finished 3d printing the front engine mount, and if the bonnet fits properly (I’ll know on Friday), I’ll flat it, crack a mould off it and make a carbon fibre engine mount – a first for me, and I think I’m blazing a trail a little there.

I’ve also been through the worst man-flu in the history of all mankind, but I still managed to have a good time, relax, read a few books and I’m currently getting through the ‘travellers’ box set on netflix.

Finally, the boxen1 of shame have been put out for recycling and don’t look too bad. Both full, but not priapic.


1 – The pleural of ox is oxen, therefore the pleural of box is boxen. Obviously.

When Engine Cranes Attack

So, this went wrong – clusterfuckingly wrong. There’s a video to show you just how wrong it went.

I was lifting my shiny new engine and shiny new gearbox into the chassis to start work on the engine mounts and I had a catastrophe. Normally when I lift it in, I take it in from the side and pivot it. This time, in order to make my life easier (ha!) I had it on an engine crane pivot mount because there was only me. The pivot mount has a cranking handle that lets one change the angle of the engine. However, what it doesn’t do is give one the same pivoting as a nylon strap.

Long story short, I toppled the crane over, into my tool chests, and smashed 5 drawers over two tool chests, and covered the floor in nuts and bolts.

Behold!

Final fitting of the tub

 

So, here is everything laid up as a reminder of where this started. I think it’s a good reminder of how far the tub has come, but at the same time it’s also making me think the duratec is photobombing everything in my garage.

 

 

 

Now, here it is in the car:

It’s pretty close to where I want it now, and I’m doing the final fettling. I made this with a positive mould, which has meant the outer surface (that fits to the chassis) isn’t perfectly flat. I’ve had to take it back a little at a time with the flap disk in the appropriate areas to be sure it fits. I developed a methodology to do this after I’d removed the obvious obstructions.

I go around the gap with a feeler gauge set to 0.7m, and look for areas it traps. When I find a trapped area, I set the gauge to 0.05 mm and see if that still sticks, and anywhere it does, I mark with tape (hence the packing tape on the tub at the back top) and take it back about 1mm with a flap disk. I deliberately only mark the jamming points rather than the tight points so I can avoid making gaps unnecessarily larger than they need to be.

Once everything is marked, I lift the tub out (it’s only 13kg, so two adults can easily lift it with fingertips) and do the sanding. When it goes back in it fits a little better. Everywhere is pretty much where I want it, apart from the back where it’s still a little high. Everytime I advance the fit, the back lowers down a bit. I have about 3-4mm left before it’s flush and I’m happy.

This one is a little more difficult to wrap your head around, but it’s the mating surface between the tub (carbon on the right, starting in the top right corner) and the chassis rail. As you can see, the gap is pretty uniform now, and I’m aiming for between 1 and 2mm.

It unfortunately means I’m doing to have to remove some of the powder coat with a flap disk.

 

 

 

Here is the birds eye view. You can just see the lip at the back. I don’t want to just sand it off – I think I can make the tub a better fir before I have to do that.

Then the final act before bonding it in is to have it lacquered and cured. Then I will have an awesome finished product.