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Learning how to build Lotus Seven replicas...together!
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PostPosted: June 6, 2021, 6:07 pm 
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I didn't realize you edited your last post to add the specs.

Why are your numbers asymmetrical from side to side? The specs are what you try to build to.
I averaged your specs and manipulated the spindle joints in an attempt to replicate them all. If you want accurate results, measure perpendicular from the joint cls to the wms on the rotor X and the axle cl Y. I also did not include loaded tire compression.
Lonnies Approximation

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PostPosted: June 6, 2021, 9:57 pm 
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@MV8

Thanks for doing the VSUP run. I looked at the main page. I've never actually run the software, so I'm not familiar with its features and outputs. Nothing looked horrid to me at first glance.

Of course, I tried to be as accurate as possible when building things. However, in a home shop, errors creep in as you go. For example. drilling a 1/2" hole through big piece of RHS, the runout of the drill press shows in the far side hole. I measured what was actually built and tacked in place using 1/2" rod in place to measure from/to.

The variations are actually pretty small, but the consequences of even 1/32" can be surprising. The chassis was built with care, but it's not perfectly symmetrical since it was done by hand and not with jigs and fixtures. The standard means of welding the brackets to the chassis (used in both Book & Haynes versions) are going to reflect those imperfect dimensions for something thus built.

In my more rational and pragmatic state of mind, I realize the car is just about always going to be loaded asymmetrically in real life anyway (with me as the 170 lb. lump in the driver's seat) and all these precise, symmetric assumptions will go right in the dumpster. So, it going to be a matter of tuning the suspension of the imperfect, built car that will really matter. I just want to avoid things that will make that task difficult or impossible.

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


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PostPosted: June 9, 2021, 2:36 pm 
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So, my next sub-project is going to be the lower, front control arms. I've been putting the components I have in place and trying to visualize what would be the most realistic design for me to fabricate.

Here's the spindle with the ball joint, ball joint housing (gray/black) and the Chrysler screw-in ring(shiny silver) mounted.
Attachment:
File comment: Next mechanical task - join to chassis.
DSC05731.JPG
DSC05731.JPG [ 162.65 KiB | Viewed 128 times ]

A closer view, ball joint centered in housing.
Attachment:
DSC05732.JPG
DSC05732.JPG [ 103.47 KiB | Viewed 128 times ]

I was surprised by the angle of the ball joint with horizontal. It turned to be 17 degrees.
Attachment:
File comment: Measuring the angle of the ball joint stud C/L off horizontal.
DSC05737.JPG
DSC05737.JPG [ 112.5 KiB | Viewed 128 times ]

The ring itself is fairly narrow at 1", which would make it a tricky target for welding a 1" diameter DOM tube too. It's 2.5" in OD, so needs a pretty big hole saw to cut a suitable hole in steel plate, but I can do that.
Attachment:
File comment: Screw-in ring diameter. Threaded inside, thickness is ~0.250"
DSC05738.JPG
DSC05738.JPG [ 129.95 KiB | Viewed 128 times ]


I like to use tape to get an idea of angles and lengths involved.
Attachment:
File comment: Tape for general dimensions/angles.
DSC05733.JPG
DSC05733.JPG [ 137.13 KiB | Viewed 128 times ]


I'm thinking a modified version of the Haynes Roadster design will be most realistic for me. It's larger/heavier than I'd like, but very simple and robust too. Here are some marked up shots of the Haynes design done in 3D. It isn't a design yet, just my first blush thinking. That's why I'm exposing it. I typically find that leads to improvements due to suggestions.
Attachment:
File comment: Marked up screen shot of Haynes Roadster lower, front control arm.
Design #1.jpg
Design #1.jpg [ 141.99 KiB | Viewed 128 times ]

Attachment:
File comment: Ditto above.
Design #1 top view.jpg
Design #1 top view.jpg [ 116.09 KiB | Viewed 128 times ]


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


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PostPosted: June 9, 2021, 7:48 pm 
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I would not worry about a swaybar until you have one to fit. The uca makes more sense to load with a swaybar than the lca imho.

I'd do something like this for the lca with the plate smaller and narrower to align the edge with the center of the tubes, fitted to the bottom instead of splitting the tube. Tube ends are tapered 17 degrees. Coilover cross tube is fish-mouthed into the tubes and is 1/4 walled dom, further outboard for a better ratio and lower so the top mount can be lower also. I'd use the same size tube as the pivot shells (1-1/4?).

I'd also use 1/8 strip/plate versus 3/16.


Attachments:
Lonnies LCA.jpg
Lonnies LCA.jpg [ 84.97 KiB | Viewed 114 times ]

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PostPosted: June 10, 2021, 10:26 pm 
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@MV8

I like your idea of tying the tubes into the ring end plate. I'll be getting back to this tomorrow.

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


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