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Learning how to build Lotus Seven replicas...together!
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PostPosted: March 15, 2021, 5:03 am 
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Finally got some time to persevere with the XBOX 360 Kinect scanner setup I wired up a few months ago. Once the correct drivers were installed on the laptop it fired up. Initial tests on the die cast aluminium parts were not good, so had to spray the surface to reduce reflectivity using Ardrox 9D1B developer (basically talc powder in spray form). AESUB makes some very clever spray that evaporates after a day, which avoids the mess I have created on the transmission adaptor plate.
Attachment:
Adaptor plate.jpg
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Reusing an old 12V 1.5A power supply, cutting off the Kinect plug and wiring to a USB has produced a working scanner for $2 NZD - the local games shop was selling its old stock of series 1 xbox kinect units - I now have enough spares for the next decade.
Attachment:
scanner.jpg
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The scan is not industrial quality - only using Reconstructme free version, and will try out a few others like Skanect - but encouraging results. Really want to scan the entire engine and trans, but not keen to spray them in talcum powder.
Attachment:
raw scan.jpg
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PostPosted: March 15, 2021, 7:12 am 
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Consider “masking liquid” mixed with fine copper powder or other reflective material, similar to a step in the process of chrome plating plastics except the coating is water soluable.

Looking back through your posts, I see a glass quote of $16,000; essentially the cost of the shoe. Have you looked at the windscreen certification steps required in NZ? You don’t have to make the glass, just trim, wet sand the edge, heat evenly to 700c to shape the layers then controlled cooling to temper, lay the vinyl between, squeeze to remove most of the air, then into a vacuum chamber to remove the bubbles so the PVB becomes clear. You seem to enjoy challenging details.

I want to see some eyeballing, cardboard aided design and dirty fingernails.

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PostPosted: March 15, 2021, 4:48 pm 
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Thanks MV8, was not aware of masking liquid, brilliant suggestion.

Have you made a windshield before using those steps? Is the shoe just a frame around the periphery of the screen? If so I don't understand how the sag of the pair of glass sheets gets controlled (assume precise time and temperature control?) I have watched lots of you tube videos about the process and with the right equipment it looks possible - but there are ZERO people set up to make compound curved glass windshields in NZ (last proper glass factory closed in 2003 - everything is now imported) . I have a source for something VERY close to original from Pilkington in the UK which I will probably consider, around 1000 GBP upfront and 8 months leadtime.

The pre-design phase has been more protracted than I expected due to LIG* & WEBR**, but frustratingly close to the end of the design application stage - currently the certifying document is running around 60 A4 pages of drawings - only a few more to go and I am done with CAD for quite some time....

Last week had a 600 x 600 x 600 Modix Big60 printer arrive at work - once I have that assembled will be making some transmission bellhousings and Tbox pumpkin patterns in its deadtime. Lots of chances to get dirty fingernails coming up!

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PostPosted: March 15, 2021, 5:22 pm 
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Windscreens on custom cars are a MUCH bigger deal than people expect. I strongly suggest compromising from "perfect" to "good enough" in this case. How about possibly using cut portions of existing windshields, maybe split it, kind of like how some old American sedans did it.

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PostPosted: March 15, 2021, 8:04 pm 
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Kinetic Research wrote:
Have you made a windshield before using those steps? Is the shoe just a frame around the periphery of the screen? If so I don't understand how the sag of the pair of glass sheets gets controlled (assume precise time and temperature control?) I have watched lots of you tube videos about the process and with the right equipment it looks possible - but there are ZERO people set up to make compound curved glass windshields in NZ (last proper glass factory closed in 2003 - everything is now imported) . I have a source for something VERY close to original from Pilkington in the UK which I will probably consider, around 1000 GBP upfront and 8 months leadtime.


Nope, I’ve not made a glass windscreen but the process is not much different from molding a bubble canopy for aircraft or making tail lights or head lights from acrylic. The temp is much higher and you need an autoclave to complete laminating process. Still a bit of trial and error but this is how I THINK it could be done and worthwhile if you plan to offer windscreens, with the basic tools to make any kind you wish:

Purchase two, regular non-tempered window glass sheets from a residential supplier. They will also precut the flat sheets and sand the edges for you.

Build an electric oven like a kiln with refractory and programmable controls that will heat one sheet at a time, evenly from above. Make sure the coils cannot sag out of the refractory into the glass. Adjust the gap between the coils of wire to ensure even heating. Buy the wire then wind it yourself around a dowel in a lathe or drill.

The shoe is steel framed to withstand the heat with a refractory basic shape and smoothed with plaster of paris. Unlike acrylic or lexan supported with clamped edges, the glass needs even support to prevent breaking while it is being heated to a formable temp. You can do this with steel dowels in a grid pattern protruding up through the shoe. When the glass is starting to sag, raise the shoe to keep the glass near the heating element and continue heating until the glass has sagged completed into the form.

Controlling the rate of cooling will determine the temper of the glass which is where the controller and thermocouple are nice to have instead of just a rheostat.

Form the second sheet the same way.

An autoclave is used to cause the vinyl to become transparent, I assume heat and pressure.

Then you have the issue of certification (dropping heavy stuff from a certain height and optical clarity) and the marking required when inspected for titling of the car.

Lots of trouble but it can be done. If at all possible, design for use of an existing approved fairly common windscreen. I wonder how much a McLaren windscreen costs.

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PostPosted: March 15, 2021, 8:30 pm 
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Good info & advice, thanks.

A few months ago I did some bend tests by draping a pair of glass strips over a stainless steel mould, we have kilns here in the foundry that are suitable for the process. You have to bend both glass sheets at the same time or they will never match perfectly when the PVB is autoclaved.

Attachment:
prototype windshield.jpg
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CNC cut out a 1/10th scale negative mould and filled it with plaster of paris to get a male mould for drapping tests. You can see from the contours that it is unlike any other screen, I have scoured the local wrecking yards, car dealers & mall parking lots with 1:1 cardboard templates in hand to no avail - but I don't give up easily so will continue the search - long time before I start bodywork due to WEBC.

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tenth scale windshield.jpg
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PostPosted: March 16, 2021, 8:06 am 
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I was referring to the McLaren F1 windscreen which appears to be very similar.

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PostPosted: March 16, 2021, 4:40 pm 
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I suspect that the genuine part would be an almost direct interchange on my car. However my research to date has found that the factory is the only source of glazing components to the owners of the 106 cars produced.

The cost stated on page 1 of this thread is from this video - https://youtu.be/73LNmkL4tfg?t=269 - and has probably gone up significantly since.

The contour of the windshield is very clever and has a relatively flat region directly in front of the drivers critical view area (the rectangular boundary shown in picture below posted a few pages earlier ) to minimise distortion, a good thing at 200 mph.

Attachment:
screen swept area.jpg
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A recent highres render of the front view
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full frontal v2.jpg
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PostPosted: March 20, 2021, 2:26 am 
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Went to a recent "caffeine & classics" event and met a fellow car constructor who built this cool midengined 4wd open top sports car using a mix of Subaru WRX and honda parts. Cleverly it utilizes a self built dry sump system using ford small block oil pump gerotors.

Attachment:
freewheel.jpg
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So I have just dropped the idea of using the stock wet sumps and will dry sump the prototype, which is a huge relief as that was a vulnerability I wanted to eliminate. Each engine will therefore have its own oil cooler and dry sump tank in the adjacent flank. The oil level will be easily checked by opening the flank panels for access, as there was no room for luggage space anyway. The gas filler cap will also be accessed by opening the left flank hatch. The relay panel, ECU's and battery are positioned on the floor behind the passengers.

During the build it is very easy to fall into a mindset, for example I have been struggling to find room to increase the capacity of the fuel tank while retaining the ability to drop it straight out of the frame if servicing is required. Completely missed that going to the dry sumps allows me to move around a few tubes near the tank and has increased the volume possible to 80L ~21 gallons.

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PostPosted: March 20, 2021, 5:29 pm 
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The filler neck will be submerged when full so you might as well make the lower section as large as practical. I think you will be able to watch the fuel tank level going down as you drive. I could in my 69 442 with a 455 and it had a 20 gallon tank.

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PostPosted: March 21, 2021, 2:18 am 
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I bet the 4-4-2 was a lot of fun while it was freefalling the gas gauge! I suspect enthusiastic driving will consume a lot of fuel, however on long runs being able to suspend one engine means the fuel consumption won't be horrific given it is lightweight, aerodynamic and has long manual gearing.

Did a scan test of the transmission assembly and the raw mesh did not require scaling, the kinect scanner determined the size by ranging the surfaces as it went. The light grey box is the original design envelope roughed out for the gearbox based on measures from real parts, however it is good to see close alignment between virtual and real data. The 2 little cylinders under the centre of the gearbox are the transmission isolation mount faces, didn't have any UNC nuts to attached the real parts for the scan, but vernier measures are reliable enough for now. Once the build approval is given will lay all the big parts out in true scale according to the CAD positions and double check anyway.

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trans assembly fits.jpg
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PostPosted: March 23, 2021, 4:51 pm 
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Kinetic Research wrote:
Went to a recent "caffeine & classics" event and met a fellow car constructor who built this cool midengined 4wd open top sports car using a mix of Subaru WRX and honda parts. Cleverly it utilizes a self built dry sump system using ford small block oil pump gerotors.

Attachment:
freewheel.jpg




Do you have anymore information on how the AWD system works? It looks like there isn't a lot of stuff behind the engine so I'm assuming it's a Transverse but how does the power get to the Front?

Glad to see you making progress on your build. This is insane in all the right ways.

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PostPosted: March 23, 2021, 5:33 pm 
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There is a reverse cut ring and pinion available but not locost to be sure. Allows you to turn everything around and fit steerable uprights to what was the rear diff(I'm guessing the honda bits).

http://www.subarugears.com/

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PostPosted: March 27, 2021, 9:49 pm 
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nocones wrote:
Do you have anymore information on how the AWD system works? It looks like there isn't a lot of stuff behind the engine so I'm assuming it's a Transverse but how does the power get to the Front?


I didn't create this setup, so the following is from my dubious memory. It is cunning in its execution and the main reason for making the engine dry sumped was so the drive shaft could pass underneath. The engine, flywheel, clutch and WRX gearbox are fairly standard items, but what is unique is the way the drive shaft that normally runs the "front diff" is adapted and replaced by a pair of speedway gears and another drive shaft that then goes to the honda CRV diff at the rear. Front diff is a subaru unit. The viscous coupling was used to bias the drive torque f/r. the trans tunnel is quite wide.

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freewheel AWD.jpg
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freewheel from front.jpg
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PostPosted: March 28, 2021, 7:32 am 
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That is clever! Definitely the hard way plus straight a cut winters gear set and then they come out with an R&P! :BH:
The total costs are probably similar but at least the builder is not locked into a single source aftermarket supplier, not that he'd ever need another R&P if it is setup right.

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