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Learning how to build Lotus Seven replicas...together!
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PostPosted: April 18, 2021, 4:56 pm 
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My old CAD workstation at home died suddenly - very frustrating event and time consuming to get back to normal operations.

The scanning of the test engine went very well, and once the main axis of the point cloud was superimposed over the original CAD block model the result was quite acceptable. The exhaust manifolds lined up quite close to the target areas.

The white area in the middle of the vee is the true gap between the inlet castings. The mesh is really quite detailed, however obtaining still shots that don't look rubbish is proving challenging - so I am not going to waste anymore time trying. The mesh looks great rotating in the dynamic view as the features on the block are easily perceived. The scanner was the best $2 I have ever spent.

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PostPosted: April 26, 2021, 2:13 am 
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There is light at the end of the tunnel as far as the paperwork goes - double checking all the sub-assemblies and part details takes time though.  Since I am only doing this the once I want to ensure that I clean up the niggly details I was leaving till the end - which is the suspension mostly.  All the fun of being behind the computer is gone and it is a real slog when solidworks keeps crashing - the issue stems from using configurations within configurations within configurations (bit like the movie Inception, even the computer loses track of where the story is up to).  Using up the last of the gumption reserves and looking forward to sending off the approval document.  Hopefully all this extra time spent in the layout phase pays back 10 fold when it comes time to fabricating and assembling, and certification will hopefully just be a rubberstamping exercise.    
Comparison shot of the C6 corvette stock geometry and the F1 both in full rebound and a C7 for reference.

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PostPosted: April 26, 2021, 3:19 am 
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C6/C7 don't look that different to the C8 in full rebound.

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PostPosted: May 4, 2021, 1:59 am 
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Rear camber change on the McLaren seems a lot! And yours seems not quite right or maybe just too much static camber (if that's at full droop). But then again, I've never built a car, haha, still in progress.

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PostPosted: May 15, 2021, 1:00 am 
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Johnsinski wrote:
Rear camber change on the McLaren seems a lot! And yours seems not quite right or maybe just too much static camber (if that's at full droop). But then again, I've never built a car, haha, still in progress.


Dude, I haven't either! Really impressed by your CNC adventures, those RC bodies are cool.

I have been quite stuck over the last few weeks trying to overcome a glaring brain fart in the detail design of the gearchange mechanism. Since the early ergonomic layout 18 months ago I had not fully appreciated how the engine rocking on the mounts would cause a significant change in the position of the selector shaft on the transaxle relative to the "fixed" shafts connected to the body. Originally I was intending to arrange the mounts so that the selector was on the pivot axis, however other constraints resulted in the transaxle selector moving in an arc centered on the low axis formed through the central Tbox mount and the pair of transmission mounts. Movement of the selector will be no more than +/- 3mm side to side, and the new gearshift shafts position and angles should not affect the gear engagement. Now the design has a tube passing through the fuel tank (clears the repositioned fuel pump) to allow a direct shot to the selector as there was no way to route around the tank. Not sure how the LVVTA will accept this idea, but as the whole concept is fairly unconventional and wacky - why stop now!

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PostPosted: May 15, 2021, 6:39 am 
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Consider making a cable shifter. I used standard, universal marine control cables and designed the trans linkage so they would stay parallel end to end and work without modification to the original shifter for ratio and travel. This is on a 1987 Pontiac Fiero with fitted with an 2000 F23 5 speed and vortec 4.3l v6. I think the cables were about $30 each new on ebay.

The battery sits above the trans. The brown trans mount bracket looks kind of odd as it picks up the original trans mount location. Like gift wrapping a horse.


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PostPosted: May 15, 2021, 7:14 am 
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A good "get out of jail card" if I need it, thanks Mv8. Shift quality is very high on the design "must haves" for this project, and given the 7 speed box has really heavy sychros it will handle forceful shifts and that is the reason I want to stick with the GM style direct shaft with universals.

What function does the drillbit do in the F23 14 pic? :cheers:


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PostPosted: May 15, 2021, 8:08 am 
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They act as alignment dowels for neutral/center of lever travel for each cable for adjustment. There are two drill bits 90 degrees to each other in the pic.

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PostPosted: May 29, 2021, 5:59 am 
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Have come up against a really ugly problem, the scavenge pumps should be on the "downwind" side of the sump pan so that windage drives the oil into the outlet ports. Positioning the pump on the appropriate side (as shown below) unfortunately results in the drive belt clashing with the standard oil filter placement (see photo of standard engine below). Stink. The goal was to keep the engines stock "off the shelf" units, but this is looking unlikely now.

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Battery, alternator and starter motor are all on the right flank which means the right motor is the primary engine. The wiring is being kept as short as physically possible. Given the fuel filler (and overflow) are on the left flank the idea was also to keep electrical and fuel systems separated as far as practical for added safety.

Need to complete modelling the suspension pickup brackets, drive shafts, dry sump tanks and engine nose mounts. The stock nose mount bolts onto the block above the harmonic balancer, will have to make a custom mount that suits easy removal of the subframe.

Thinking the rear deck lid will have to be made out of aluminium, since it is adjacent the cats and there will not be any gold plating on this car so unprotected composites will cook.

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PostPosted: May 30, 2021, 8:47 am 
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A remote filter between the pump and block isn't bad if you can keep the lines and filter from draining back after shutoff. Belt replacement means disconnecting the AN line on the fabbed adapter plate between the crank and the pump.

A thin stainless sheet with a layer of silica mat and an air gap to the composite and cats should help. Mesh panel between the tailights to aid flow?

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PostPosted: May 31, 2021, 12:16 am 
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Good ideas MV8, much appreciated. I will try a swatch panel to test & measure the temp gradient.

Good result today for the exhaust stubs, they are off to heat treating tomorrow then machining in a few days. 2 of them will be ready for bolting onto the primary test engine in the next few weeks just in time for fire up!

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PostPosted: June 1, 2021, 10:31 am 
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Location: Cornholio OR "Where the magic happens"
You can scavenge the pan from the opposite side by sticking a tube into the pan across to the other side.

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PostPosted: June 1, 2021, 2:35 pm 
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Bent Wrench wrote:
You can scavenge the pan from the opposite side by sticking a tube into the pan across to the other side.


My list of people to thank for getting this creation across the line grows by one - thanks Bent Wrench that is quite a simple solution that I couldn't see for the trees. I was going to mill the pan out of a block of billet, no reason why I can't put passages under an internal plate to the ports on the opposite side and achieve the same result.

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PostPosted: June 4, 2021, 11:05 pm 
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Whoa! Did you do the casting? Nice. Need the deets.

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PostPosted: June 5, 2021, 2:53 pm 
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The castings were from PLA patterns made on a Creality 3D printer at 0.2mm layer thickness. The CAD file of the part was scaled up before printing to compensate for the metal shrinkage allowance. Wall thickness is 2.5mm (0.1") and material is a cast equivalent of wrought 330 stainless steel. The exhaust will be wrapped with thermal bandage and a heat shield placed between the front bank exhausts and rear bulkhead to reduce the heat soak into cabin and fuel tank. Clearance between the exhaust stub and bulkhead is 2" at the tightest point so enough room to put a heat shield in between. Some of the air from the roof scoop will divert down to cool the area between the heat shield and the bulkhead, which has the passenger seats molded in. Engine rock does not change the clearance due to the Tbox and transmission mount positions. Raw casting cost would be around USD $175 each ex-works if done for a customer.

The original honda exhaust stub looks similarly restrictive yet still manages 270hp, so once the Tbox concept is proven out in the rolling chassis test mule I might be able to get some help from someone with a flowbench and engine dyno to try and improve the geometry. Engine development is not on the current priority list as the goal is a road car, but longterm plan is to regrind the stock cams. Combining extra valve lift, head porting and dry sump setup a reliable 325Hp should be achievable, aided by Speeduino ECU lifting cutoff to 7500rpm. Then multiply result by 2.


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