ESC 750 Mk2 – progress

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ESC 750 Mk2 – progress

Postby EmlynC » Sat May 25, 2019 6:03 am

I read with interest all the comments about which CAD software to use (we are using Solidworks), and Martin's comments about just designing on a drawing board (as I do) and making by hand. For the most cost effective route he is certainly right – to go CAD design and, as in my case, then laser cut and jig build for a one-off car is bonkers from a financial point of view. I had no idea just how deep a hole I was digging, but I have gone so far that I now just have to keep going.

Yesterday I went to Caged to see the laser cut tubes, the the two large laser cut 2,800mm x 1,250mm x 10mm steel plate jigs with holes cut to position all the locating lugs. I was like a little boy on Christmas morning – after working on the project for eight years here where the actual tubes and panels that will be the first chassis, and the cost became far less important. The quality of the laser cutting is simply unreal, and it allows you to design in a totally different way – to hand cut multiple round tubes coming to a single point would be almost impossible, and certainly not easily repeatable.

In the future I will have a significant decision, as, to be cost effective, I will have to produce a batch of at least five chassis, but I don't think anyone else will want to commit until seeing how the first car runs (hopefully next season).

The chassis is going to be welded over the coming week, starting today, by Tommy who is the person who welds all the BAC Mono chassis – so I will post shots during the build. The target is to have the main frame with dummy engine and gearbox in by next Friday, when it is due to be delivered to BTB to have the exhaust system made (interestingly their quote was £1,000 less if they make the system by hand rather than from CAD files).

Here are the six shots (three in each of two posts) which I hope will show why I’m so excited.


All the shorter tubes for first chassis
IMG_0011.jpg (123.57 KiB) Viewed 3550 times

All tubes are individually named and numbered
IMG_0015.jpg (74.44 KiB) Viewed 3550 times

Jig for the top of the chassis placed on the 3.6m x 1.8m surface plate
IMG_0046.jpg (138.27 KiB) Viewed 3550 times
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Re: ESC 750 Mk2 – progress

Postby EmlynC » Sat May 25, 2019 6:11 am

Another view of the jig on the surface plate
IMG_0049.jpg (134.13 KiB) Viewed 3549 times

Detail of tubes held in place by the positioning lugs
20190524_153718_resized.jpg (75.84 KiB) Viewed 3549 times

Panels have been laser cut with their rivet holes and folded
IMG_0010.jpg (121.66 KiB) Viewed 3549 times
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Re: ESC 750 Mk2 – progress

Postby F1300Tony » Sat May 25, 2019 3:37 pm

You might finish up with the only 750F with more than one spare chassis! What gearbox are you using?
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Re: ESC 750 Mk2 – progress

Postby EmlynC » Sat May 25, 2019 5:20 pm

Hi Tony,

I could, but it is not the intention! I will need to have at least two people interested before committing to the first batch. The really exciting thing is that every chassis will be identical.

I had done too much work on the design with the Fiat gearbox, so I'm sticking with it. I have ordered (paid for but not arrived yet) the "standard" Bacci Romano close ratio gearkit (RC070), plus a special final drive (which I suspect is the reason for the delay). The close ratio gears only work in the earlier (pre needle roller bearing) gearbox, but to change the crown wheel you need a later gearbox where the crown wheel is bolted on with ten bolts.

Below is today's progress.


The top chassis which is now welded. The small slots are location points for the vertical tubes to slot into.
20190525_104940_resized.jpg (118.45 KiB) Viewed 3512 times

Starting to lay the tubes for the bottom of the chassis in position
20190525_104929_resized.jpg (102.16 KiB) Viewed 3512 times

Why I wanted Tommy to do the welding – it must be wonderful to have such skill.
20190525_105023_resized.jpg (75.93 KiB) Viewed 3512 times
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Re: ESC 750 Mk2 – progress

Postby dopdog » Sat May 25, 2019 6:26 pm

Looking great can't wait to see the finished chassis
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Re: ESC 750 Mk2 – progress

Postby EmlynC » Wed May 29, 2019 8:30 am

Thanks "dopdog" and all the other people who have said that they are enjoying my posts.

At Mallory Ed Pither described the process of building a 750 as like eating an elephant – needs to be a bit at a time. I feel it is like transporting a series of supplies to Everest Base Camp, and only when all the elements are in place can you start you attempt on the summit. In last few days it feels as if the clouds have cleared and I can at least begin to see the mountain still to be climbed.

The chassis is coming on well, and due to be completed (less some of the smaller brackets and the front and rear subframes) by tomorrow evening.


The base layer of the chassis in the middle of being welded
IMG_0079.jpg (125.6 KiB) Viewed 3411 times

Top layer just rested on four uprights to start to show the overall volume
IMG_0112.jpg (142.79 KiB) Viewed 3411 times

With the seat roughly dropped in position
IMG_0107.jpg (143.6 KiB) Viewed 3411 times
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Re: ESC 750 Mk2 – progress

Postby Dave Robson » Wed May 29, 2019 5:08 pm

Thanks for the photos and progress reports.
I understand your excitement at getting some hardware back and the CAD model starts to become alive!
I went down the route of CAD design in Solid Works and can confirm that it is not the quickest route or even the most sensible for making just one car (or dare I say a small production run). There's a lot to say about drawing on paper and then getting in the garage to make bits to prove your design. For me, I wanted to learn CAD and experiment with that technique plus some other ideas. For example I wanted to see if you could incorporate models derived from 3D scanning where the geometry is difficult to define by normal CAD generation. I managed to scan the engine, gearbox, driver and other 'blobby' items (comments awaited!)
Car ISO.JPG (73.81 KiB) Viewed 3387 times

This worked very well on the whole and allowed me to allocate space envelopes within the car. It wasn't perfect however when I found the helmet to be above the roll bar once everything was built! I now know that the driver's posture is a big variable and this is where a session in a garage mock up would have been the sensible route.

I too went down the laser cut route for the sheet metal components for the chassis and suspension. I found this not to be too expensive since I was prepared to be 'fitted in' when production runs allowed. This was frustrating at times but proved to be OK since there was much to do during the waiting times.

Having an accurate CAD model plus accurate laser cut items is a bonus in generating accurate chassis geometry and thus suspension geometry so I do feel that 'down the line' I'm reaping some benefits by taking this approach.

I was going to include further photos of the laser cut sheets but I'm not clever enough tom work out how to add extra photos after you've added text!


Dave Robson
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Re: ESC 750 Mk2 – progress

Postby EmlynC » Wed May 29, 2019 8:59 pm

Hi Dave,

I have to say that I'm really impressed by your CAD work – CAD has been used but I have not produced the CAD files. Working with the students at Brunel University, who have done the majority of the CAD design, has been one of the highlights of the project.

I have spent a great deal of time making, and adjusting the cockpit area in MDF. I wrote an article called "first make your seat" at least five years ago – I'm now on the fourth version of the seat, but I'm pleased with it now. We also looked carefully at the height of the roll bar, and also the height of the supporting diagonals.

Overall it has been a process of drawing on paper, making full size MDF / wooden mock-ups and then getting the CAD work done, before laser cutting.

Here are a couple of examples of how the approach of CAD and laser cutting has really helped:

rear mount.jpg
Multiple round tubes creating the position for the bottom rear suspension
rear mount.jpg (71.48 KiB) Viewed 3364 times

mounting for pedal box.jpg
The position of the seat is fixed, so the pedal box needs to be adjustable. This is the underside of the mounting points
for the pedal box
mounting for pedal box.jpg (123.37 KiB) Viewed 3364 times

The chassis has really started to come together – one of the advantages of having all the tubes pre-cut is the speed that they can be assembled. As you can see it is not going to be the lightest chassis ever, but the students were getting very high results when they calculated the torsional stiffness. I have gone for a longer wheelbase – it took me a while to get my head around an increase in wheelbase transfers more weight to the front of the car. The space was added between the driver and the engine, and this has give space for a perfect triangulated structure linking both sides of the chassis, and is the mounting point for the front engine mount, using the 12mm plate that has allowed the engine to be turned relative to the gearbox. It also gives more space to fit the exhaust system.

There will be a 25mm honeycomb panel running down the offset side of the cockpit.


chassis.jpg (247.74 KiB) Viewed 3364 times
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Re: ESC 750 Mk2 – progress

Postby EmlynC » Sat Jun 01, 2019 10:07 am

What a week - to go from a pile of tubes to a finished main frame in four working days. I will call it a chassis when all the brackets are added.

I had a slot booked at BTB for next week, and Caged have gone the extra mile to make sure the frame, with empty engine and gearbox in, was ready for Thursday evening. They are a great team to work with.

I can't tell you the exact weight as they don't have a large scale, but I was surprised when I tried lifting the back and found I could do it easily with one hand. Will, their lead engineer, did say that, with the thin tubes they have used, it is far lighter than either a Westfield or Mono chassis (both of which they make).

I had sent a couple of shots to Clive Chapman in the week and he came back asking about weight and torsional stiffness. I replied that I thought his Dad had said, "nothing is lighter than nothing" but he came back and with the exact quote, "nothing is lighter than a hole". The students did some calculations on the torsional stiffness and got some very high numbers, but I have not had time yet to test to see if theory and reality are the same.

There is going to be an additional Y frame across the top of the engine bay, but this has not been made yet. In the Batten, Tony managed to get a straight tube across the engine bay, but I have ended up with a slight kink, and the need for an additional short tube into the top corner on the passenger side. I should also say that I stole Tony's idea for a bent tube to take the top seat belts mountings.

Seeing the first body panels was exciting, but having a frame feels like I'm really starting to actually build a car.


ps It is great to see just how may people have been following the posts this week – I hope you are enjoying watching progress.

IMG_0186 1.jpg
Overall frame with engine / gearbox
IMG_0186 1.jpg (138.32 KiB) Viewed 3268 times

The height of the main frame is 266mm (10.5" originally).
IMG_0187.jpg (130.11 KiB) Viewed 3268 times

I'm really pleased by the way the engine / gearbox dropped straight in. I know that I work with different people where I don't have the skills needed, but the sump is totally my own design and I made the tooling. I watched them (three off) being cast, which was a very interesting couple of hours.
IMG_0175.jpg (137.19 KiB) Viewed 3268 times
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Re: ESC 750 Mk2 – progress

Postby dopdog » Sun Jun 02, 2019 4:48 pm

I like it more everytime I see this. Great work and look forward to seeing the next instalment
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