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Thanks for the tip 713bt, would that work with an MDF plug?

Photo below shows a half plane section 1:10 scale model of the interior plug sitting on the partially built fullscale example. The cornflake boxes have proven to be superb at supporting the MDF sheets while cutting out the profiles using a circular saw and jigsaw. Doesn't matter if I cut into them and they are very easy to reposition for odd shape cuts. Plus they were free and I still have lots leftover for Nerf war fortresses. Have set 2 degrees draft on these vertical faces so release should be easier - busy waiting for glue to set.

The 2 mirror image interior panels join down the entire centerline. The panels enter the interior through the door aperture and can be installed into or removed from a completed spaceframe.

As long as the MDF is sealed with some type of paint before the mold release is applied. You should apply some paintable silicone caulking to all the joints/seams first. Smooth the caulking with a template (or just a finger-tip) to get a small radius fillet.

Interior plug is progressing with fairly cheap materials - MDF, PVA glue, some screws and duct tape. Once all the little panels are fixed in place the edges will get small fillets and the plug will be sprayed with Prestec 2093 primer as with the rear panel.

Radii added and epoxy bog applied to gaps, next some sanding and primer.

Happy new year to all. It seems like the last 12 months went by rather faster than usual. Really going to have to focus on increasing my output in 2023 or this thing is not going to get completed.

Interior plug has first patchy coat of primer on it, very proud of the overall accuracy and alignment of both sides, it is within a few mm of the latest CAD model. The passenger seats are really comfortable with a bit of padding in place, so all the fussing and delay was worth it. If this plug survives the polyester tooling being removed (and I will be doing a lot of waxing to ensure it does) then it will be kept aside for the final carbon/epoxy tooling in a few years time. Polyester/glass is fine for the test mule.

Now that the bottom of the door aperture is tooled the door design and final hinge detailing can progress - using dummy doors initially. Doors really force a decision on windscreen selection - a problem that has been put off for as long as possible as there is no good "off the shelf" option currently.


It was interesting to reflect on the very subtle changes compared to the original CAD model from early 2021. Biggest improvements are fuel tank cover size and position and all footwells being properly sized.

This is going to be quite a vehicle. I'm hoping you have a very positive outcome on this piece. I imagine pulling the finished part is going to be a challenge given its size.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Hi Lonnie, yes it's an intimidating piece in person, however the bottom of the seats and the nose floor are removable panels - once the tool is formed in the plug and has set solid the whole assembly is jacked up in the air and the panels are removed. I will then lower it onto some 2x4 timber so all the weight is bearing on the lowest (and most reinforced!) points of the mold. With the 2 degree draft per face a few solid blows downwards onto the plug outer edges should break the whole thing free as gravity is doing all the work to pull the plug off the mold, which should just be left suspended on the wood once the plug drops. Time will tell, the layup will be slow to minimise shrinkage as this is a plug intended for epoxy tooling which shrinks less than the polyester.

Making big molds stable in multiple orientations is definitely an advantage. Finding and repairing all the little surface defects is certainly easier once the first primer layer was applied. Second primer layer went on much easier in the vertical position, last primer layer today then sand flat with 240 grit then 400 grit.

Due to the gap caused by the removable passenger seat panel a pile of bog shavings was able to fall out when disturbed by the spraygun blast, out onto the freshly painted left passenger seat. I hate it when that happens.

While waiting for paint to dry progressed the front left upper wishbone and coilover mount, will cast this and check the result before making the RH side. Will be simple to change the caster and camber angles by unbolting this unit and replacing with one with the wishbone mounts in a different position, intention is to not have to modify the spaceframe while tuning the handling.

Waxed the plug multiple times, added fillets to all corners and sprayed all over with PVA release film.


Had to work very quick to get this all spread before it gelled, one area had slump which thickened and went off quicker than desired. A small amount of sanding tomorrow and another coat of gelcoat should smooth the surfaces out enough to progress to layup.

Tissue and a couple of layers of 200g/m2 bidirectional glass cloth have been applied to the plug but some major lessons learned on getting faster at layup. Made one big blunder and took too long with one section, resin started to get cheesy on the other side and I had to pull it off and chuck in the bin before it set on the plug. Good thing is the resin mostly went with the cloth so cleanup the next day was simple.

Have really struggled with getting tight corners to conform if the cloth is long, basically playing whack-a-mole with bridged cloth, stipple it into one corner and the tension pulls out the corner done previously. Now using 3" wide tape to reinforce the corners and cloth panels between the tape, very easy to work the cloth into position and the bubbles and kinks out. Top flange edge is a little shorter than it probably should have been so clamping coreflute strips on while curing to keep a nice sharp flat edge, otherwise the cloth seems to want to curl off and cannot be moved once set. A few layers of chopped strand mat to go then the big moment.

Victory! Plug sacrificed itself but the mold is fine so pretty damn stoked. Now just need to take a part off the mold and I can finally get onto the build table.



The trial Left Front Upper Control Arm mount casting went well, material is carbon steel to BS3100A4, 320 Mpa yield min. will make the RH one then start on the front and rear suspension on the build table.

Congrats on the mold completion. Looks good.

Have the full set of shock mount castings made, bit of surface clean up then off for normalising heat treatment. Some simple machining then the parts will then be ready to weld to chassis tubing.



A bit of rear subframe detail showing the handed rear shock mount castings in situ. I like triangulation.

Do you do your own casting? If so, what do you use for a furnace?

One of my (very distant) memories of shop class in high school was how difficult it was to weld cast materials. That was back in the days when we only had stick arc welding and oxy/acetylene to work with. TIG (then called Heli-Arc, I think) was an exotic method limited primarily to aerospace companies.

Are you going to TIG weld the cast materials to the tubes?

Cheers,

EDIT: I re-read your graphic and see you clearly said TIG weld.

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886