Category Archives: chassis

Testing Carbon Fibre before I commit – Part 2

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So, here is the raw results file:

raw data

I’ve kept it there in the spirit of honesty, but the following distilled data into the graph is what really matters:

new graph

 

So the numbers that matter are those on top of the line – each of those is the number of KG force required to deflect the part by a given distance. You can correlate the colour to the number to the data in the top chart (click through for details)

Finally, there is the density/deflection ratio, which would show the ideal performing part if absolute strength wasn’t the most desired outcome.

density

Conclusions

There is a trade-off between core and layers, which is what would be expected. What actually surprised me the most was the difference a core makes.

The top line has two variables set – 4 layers of CF (rather than 2), and a 10mm core, rather than the yellow line, which is 4 layers and a 6mm core. The third highest line is the darker blue line, which is 2 layers and a 10mm core.

So, it’s layers over core but again, there’s a trade-off. The red line is 4 layers over a 3mm core, and you can see it yielded really quickly at 3mm with a very low amount of force (well, 98kg of force). Without doing any statistical analysis, I am observing that each 3mm of core seems to give me an extra 100kg of resistive force before yielding. However, I don’t know how far that scales.

Finally, you can see that there are a selection of flat lines near the bottom, and they are parts made without core. The seem to bend a lot and not yield. For my purposes though, they’re not suitable. Parts 6 and 7 (four and two layers), deflected up to 7mm without yielding, but weren’t much use to me.

As the thicker parts started to yield, we could actually hear them crack (quietly). I’m assuming that’s the fibres snapping. As such, the moment it starts to happen the part is compromised.

wrongness 6 – angle grinder accident

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wrongness 6 – angle grinder dies

So, after 20 years of faithful service, my bosch angle-grinder only goes and dies. Smoke came out of it and that was the last turn it made. I replaced it with a cheap hitachi and kept on going. There’s a lot of steel seam-welded in this car and it can be a real pain to get it all grinded out. Near the end of the day, I was starting to feel like I’d had enough, but was wanting to get one corner finished.

Therein lies the rub :). I was wearing a jumper and managed to get the left sleeve of my jumper caught in the grinder (I think I was holding it in my right). Before I knew it, it had whipped the grinder out of my hand, and as it started to spin on the sleeve, it dragged the grinding disk up my arm. Then it stalled.

I don’t like thinking about what it would be like if I had a slitting disk in there rather than a grinding disk.

Here’s the obligatory photo though:

IMG_0892

Chassis cut out now, ready for part manufacture

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IMG_0894So, now I’ve managed to get the entire squabs and transmission tunnel cut out, ready to take the entire floorpan CF part.

It looks somewhat bare and scary, no? Overall, I’ve cut 22kg of steel and ally out of this arrangement, and some of it was especially difficult to get out. I’ve also cut out the harness mound points out as well – I’m going to reposition these as hard points in the composites when I know where I want the seat.

I’m going to go for post-fit hardpoints, in a sandwich arrangement. What I will do is drill the hole through the tub for the eyebolt hole, then use an allen key in a drill inserted in the hole to worry out the closed-cell foam core, and then I’ll fill this hole with an epoxy/glass bead filler. This will create a hard point to bold through.

In order to be belt and braces, I will also then put a bonded in stainless plate on the front, and the harness mounting plate, bonded on the back. This should give great anchorage. I will make a test panel as well to test this.

Footwell Fettling for Friend’s feet, Part 3 – Finished

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footwell part 11

Right, so, you’ve seen the video about laying up, and here is the final layup ready for the vacuum bagging stack. It also shows extra corner bracing and there are similar reinforced corners underneath in aramid.

 

 

The stack I have gone for is as follows:

  • 6 layers of mould release wax to ensure a good barrier and a shiny finish
  • one layer of GC50 clear gel-coat to give it a good shiny finish and UV protection (which it won’t need under the bonnet)
  • three layers of chemical release agent
  • 2x 350gsm CF, for the initial outer facing layers
  • 1x 250gsm Aramid for intrusion protection
  • 1x 200gsm e-glass for a little bit of flexibility in the part
  • 1x 3mm soric for the core
  • 400g of infusion epoxy mixed with 120g of catalyst (slow)

footwell part 12Rather than go for a standard side-to-side infusion I went for a circular infusion down to the centre. This stuck me as better because going edge to edge would require the resin to also climb back up the vertical slope and could spend time infusing into the corners. The vacuum will drag it up eventually, but it could be a pain. Furthermore, if there is a long wait as it gets into the final corner, you end up with the situation where resin is going into the catch-pot and the part isn’t yet fully infused (which is money down the drain). At least this way the infusion is relatively uniform, and gravity is acting on my side.

Once infused, I baked it at 50C for 12 hours in the oven, and then pulled the infusion stack off. Following is the video of me using the air-line lazy method for getting the first part of the stack off (the vacuum bag). I also used a new kind of peel-ply (knitted rather than the standard spikey flat stuff). It’s great for this kind of infusion because it will pull under vacuum into all the difficult corners. However, it remains a little stretchy after infusion, so it requires more effort to tug/haul/swear out.

 

Once the entire infusion consumable stack is removed, the part is left in the mould and the second stack is laid upon it in reverse order (without the GC50). The mould performed well and managed to split without too much trouble and about 50-75g wasted resin. I know Warren (who manufactures parts at volume) has a much more refined process for managing resin amounts – he writes the amount a part needs on the back of the mould. My parts are one-offs, so there’s no need to stress about that.

 

footwell part 14Once I had split the mould, and got the first half off, the second gave up the ghost really easily and I had a part! This was a hell of a moment because it’s the first time I’ve gone from idea to composite part in 3 dimensions. On the part you can see the extra shiny side, which was incredibly easy to get to. I washed the chemical release agent off with warm soapy water (didn’t seem to make much of a difference, to be honest) and then I put a little Farcela 300 Polishing compound on to a cloth and gave it a bit of a rub – no real application of elbow grease required and this is the result.

footwell part 15 The part has been partially trimmed (dremmel with a steel slitting disk, P3 safety mask) and offered up and it’s a great fit. You can just see the deliberate fitting gap between part and chassis, which should be between 1 and 2mm for the adhesive to work well.

 

 

footwell part 17This time the view is slightly different in order to show the clearance a little more between the part and the chassis. I had deliberately left a min of 5mm to allow for some absorption in a side-ways impact. I could have taken the footwell deeper if I hadn’t welded in the extra strengthing bar you see there to complete the cradle around the engine.

 

footwell part 18Sorry about the crap qualitty of the photo, but this is where you shove your feet. It has been sized to take size 11 trainers so most normal feet will fit fine. For final fitting, I’ll trim that remaining lip off, and bond the part of the contacting edges only. If I decide to go belt-and-braces, I will make some 90 degree angle and bond that onto the chassis and wrap it around on to the part.

Stronger than steel, far better shape, and I’ve not yet made a weight for weight comparison with the steel I cut out. I’m proper thrilled.

Footwell fettling for friends feet – part 1

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So, bugger the old passenger footwell. It displeased me because it was at 90 degrees to the floor, making it super uncomfortable for anyone over 4 ft tall.

This displeasure became one impulsive moment with the air-chisel and flap disk and it was out. Of course, the solution is composite.

The specification for the new footwell is to :

  • have it angled for comfort,
  • gain 75mm travel for feet
  • add some kind of surface ridges for strength and grip
  • accommodate size 11 trainers
  • be lighter than the steel that came out
  • be stronger than  the steel that came out
  • have superior impact resistance in case of the clutch letting go
  • double up as a foot-brace for passengers
ancle cracker

ancle cracker

The Original Footwell – here it is, and obviously at 90 degrees to any sane sense of comfort. Furthermore, the Fury footwell is quite short and anyone over 5’8 is going to struggle to be comfortable. You can also see the rust on the left and the carbon/aramid trial floor panel I made.

 

 

 

 

 

IMG_0100

First Fit of the Footwell. So this is the initial first fit of the footwell. It’s been deliberately designed to have a gap between the chassis members on both sides in case of an impact. As well as this there’s a gap of 1 mm between all aspects of the footwell and the chassis members again to allow for epoxy adhesive. It’s been made from sheets of 3*450 gsm chopped strand mat.

 

IMG_0099Here it is looking down from the top. You can see how it gets close to the chassis members to give the most leg room and foot room possible. It also has to get close to the starter motor and avoid the bell-housing but has to give enough room to get a spanner in there as well.

 

 

IMG_0018

Initial Bonding.  I used ISOPON P 40 chopped strand matt body filler compound used to give the initial bonding. It’s very strong and very quick to set; generally it will set in under 20 minutes, rock hard. This is much better than hot-melt glue which leaves a residue that you can’t sand.

 

 

IMG_0098

Reinforcement. once the ISOPON had set I have then reinforced the joints with expanding foam. This adds nothing to structural integrity but later I will need to cut into the joints in order to put the quadrant beading in place. The expanding foam gives me something to rest the quadrant beading on. In this case I will use body filler to stick the beading to the foam, and what survives of the P40.

 

IMG_0102

And so to bed. he is the part ready for final finishing. You can see lots of gaps which will need to be filled with body filler. I also need to cut all of the 90° corners out and replace them with quadrant beading.  I use quadrant beading to give a large radius because carbon fibre does not like going round sharp corners. If you leave it with sharp corners then there’s a good chance there will be bridging and associated voids and weaknesses.

 

today Warren*, i are mostly making …

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flat panels out of 3 layers of 450g CSM.

The plan is to try and get four panels made, ready for the next stage of the tub, which is the sitting in squab part either side of the transmission tunnel. It’s also a chance to practice my wet-lay technique.

 

photoI also think that if I am skinning both sides of a steel space-frame section with a diagonal in, then I don’t need the diagonal at all. Come to think of it, how brave should I go – make a full panel and dump the steel altogether? I could make a full panel and use a CF tube as a cross-brace if I wanted. If I made a panel it could be made from front-to-back uni-directional so I will be able to do it in two skins and a good core layer

Repeat to self –

I will not replace all the steel for a composite tub.

I will not replace all the steel for a composite tub

Now that I’m off to make the panels out of poly-resin I’m doing it outside, so hopefully I won’t poison the household.

Things to remember when getting stuff sandblasted, involves duck tape.

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So, I’ve sent more parts out to the sand blasters and powder coaters and I forgot a cardinal preparation rule, and have paid a minor price for it. I’m writing this post as much to remind myself as inform anyone who may be going down this route.

So, if there’s stuff you want protecting, you don’t wrap in in duck tape. You wrap it in newspaper, then you wrap over the newspaper with duck tape. If you just wrap with duck tape then the heat of the coating process melts the adhesive and sticks the tape much more tightly to your piece. Hence you wrap the paper around it first. What you get back is a really stiff mess that can be easily cut away.

If you wrap it in paper and only seal the ends with duck tape, then there’s a chance the blaster will go through the paper, and very find sand at 90psi will get everywhere.

In my case, it went into the steering column top bearing, which couldn’t be removed (due to the weld-on quick-release boss). So, I’ve washed it out, air blasted it and now I have to hope for the best (i.e. pack it with LM grease). it doesn’t really do much – just provides a loose top mount for the column. Worst case of all is that I ditch the column outer and use a rose-joint at the top to support it.

So, silly me.

The good news is that you can get universal-joints blasted and powder coated (think steering column lower linkage). Rather than try and protect them, I just thought I’d take a chance and if they were mullered then I’d make my own.

They came back looking lovely, and the gentlest of turns cracked the seal around the joint mating surfaces and they work a treat. The heat when setting the coating didn’t make any grease leak out of the seals. Some good news then.

Using my scissor lift to its near maximum potential

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So, I suppose there’s a rule here.

This is a picture of my car chassis, 5ft up in the air to put the new pedal-box at a sensible welding height. I’ve never had it this high, but it makes a difference.

What you see are a pair of hydraulic pallet-lifters bought from ebay for under £100 each. They’re stable as buggery (or rum, sodomy and the lash) and each is rated to 350KG. Bearing in mind the fully laden car with me in it tips the scales at under 700kg, all is groovy.

Normally, I have one of the scissor lifts much nearer the front but without the engine in, it balances quite nicely where it is.

Fury Front Anti-Roll Bar

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I have my front ARB in place and I must say, I am exceedingly happy with it. I didn’t make it myself but comissioned Cornering Force to make it for me. It’s part of a matched pair (one for the rear as well) which was bespoke manufactured for my layout, corner weights and aspirations for the car. I can’t recommend these guys enough. Simon is a leader in the field and has his suspension on cars on pole in the BTCC.

So, to the pictures.

This is a view of the completed, powder coated rocker arm, showing the drop link going down to the blade, set in ‘fully priapic’ mode. There are a couply of other positive observations here – you can see how neatly it’s tucked under the rocker, as well as getting a nice view of the locking pin. The pin is spring loaded, and you just pull it out, turn the blade and it clicks home.

My car is only going to weight 650KG with me in it, so we only need one blade. Both sides are coupled of course so one blade does the work for both sides. The blade itself goes through 10 different metallurgical processes according to Simon so it will last the distance. It’s the single most expensive component in the arrangement.

Here’s a good view going into the adjustor, showing the nylon bearing block as well. As you may have noticed, I’ve decided to make all parts that bolt on to the chassis blue, and the chassis will be yellow again. There are small stops welded onto the ARB to secure it to the nylon bearings.

 

Here’s the final view, on the fixed link side. Nice and simple. What should also be evident (and is also clear in the top picture) is the line of sight between the chassis force node (top rail where the vertical meets it) and the far corner node where the suspension mounts. If you look at this and the top picture, you will see where the next set of cross-bracing is due to go in. I will make this cross bracing demountable otherwise it won’t be possible to get the right angle of pitch when extracting the engine.