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Learning how to build Lotus Seven replicas...together!
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PostPosted: March 12, 2021, 10:24 pm 
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TRX wrote:
> "packing" of the front frame brackets will be necessary. They're talking about the slight gap at the front of the brackets due to the slight twist in members
----
That falls into the "ugly, but seems to work OK in practice" zone.

An alternative is to use the hacksaw and Dremel or angle grinder and cut a triangular divot out of the face of the frame tube and sink the bracket down into the tube on one side so it lines up with the other bracket.


You're probably right on the "OK in practice" designation. With clever placement of the packing, and big, fat weld beads, they'd probably work fine. It just seems like a poor compromise to me. One that you'd make on a seat frame, but not the critical front suspension brackets. I'll see if I can do better.

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: March 13, 2021, 10:14 am 
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Have you thought about making the suspension bracket a 2-piece assembly. Jack sells them now but I think in your case you would have to make custom ones to get the angles you need and to align the holes.

https://kineticvehicles.com/ControlArms ... lebrackets
Attachment:
jacks.jpg
jacks.jpg [ 59.33 KiB | Viewed 814 times ]



BTW, shimming isn't such a bad idea. I did that on my build. After tacking in the front piece, I later added triangle pieces top and bottom.

Attachment:
shim1.jpg
shim1.jpg [ 66.45 KiB | Viewed 814 times ]

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PostPosted: March 13, 2021, 11:30 am 
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@rx7locost

Thanks for those suggestions, Chuck.

I did consider using Heim joints at front, but decided on bushings for some practical reasons. Jack's brackets assume Heim joints, so they're a good fit for my choice.

I appreciate the input on shimming. I was primarily worried about distortion (big MIG beads = big heat = big distortion) and having a weak area in the critical front suspension, especially under braking. I had an interesting and relevant conversation with Perry (horchoa) last night on the telephone, and he too was reassuring about "packing" gaps and welding. I think Perry's built more Locosts than CMC now, so that was good to hear.

I haven't reached my final placement yet, so I'll wait and see how much of a gap I end up with, and then decide how to proceed.

Thanks again,

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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: March 13, 2021, 11:47 am 
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I would sharpie a line around the lca brkt, notch the frame tube as needed (or up to the wall thickness of the brkt) to put the axis where it is supposed to be, weld, then add 1/8" strip at the front and rear the width of the brkt flange (2.5" guess from pic?), that reaches the inboard corners of the frame tubes. The brkt is much stronger and thicker walled than the frame tube. I recall seeing them ripped out of the frame before.

Have to come up with a nice design to support the lca rear brkt.

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PostPosted: April 3, 2021, 11:09 pm 
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It's been almost a month, but all my real world chores are done now, and I can get back to my Locost.

I had been changing things fast and furiously in terms of the front suspension brackets and suspension geometry when I left off last. My first task was to make sure I was working with the latest data, and all the data from various sources like the suspension analyzer software, my notes and the brackets themselves all matched up, apples to apples.

Once that was done, I restablished the lower, chassis-side, A-arm brackets to a close approximation to my 3D model. I can make that work. Then I tried some general configurations of the upper brackets using what I had made already, just to see if I could make those work. They're not a good match, but I at least verified I could place the upper brackets at the desired height to get my roll center down to near 1" off the roadway.
Attachment:
File comment: My proof of concept mockup of the brackets. The two lower brackets are as before. The gray, upper front bracket is just the front bottom for the passenger side used as a trial. The dark gray rear, upper is my original V1 bracket that I thought might work. It doesn't.
DSC05679.JPG
DSC05679.JPG [ 135.71 KiB | Viewed 678 times ]


I'll need to come up with a modification of what I have on hand now. I think I have an idea. The rear, upper bracket is going to be an odd one, but my idea might simplify placement, yet be simple to put in correct alignment.

The front upper is sensitive to fore and aft location due to the nose cone. I think we're good. I'm going to make the upper brackets smaller than the ones shown here, which will look cleaner and place easier.
Attachment:
File comment: Front upper has to avoid the glass fiber nose.
DSC05678.JPG
DSC05678.JPG [ 132.55 KiB | Viewed 678 times ]


Fortunately, the front lower bracket looks pretty good. I can move it forward a little bit, which I may do to make it possible for the steering rack to move forward a little as well. My steering rack has arrived, but I haven't even taken it out of the box yet. I can't really fit it out until the suspension brackets are finalized.
Attachment:
File comment: Approximate location of the lower, front A-arm bracket
DSC05675.JPG
DSC05675.JPG [ 132.11 KiB | Viewed 678 times ]


I did discover one little issue. My build table top has gone out of level. Thay may muck up my jig making, but I'll see if I can fix it. If not, I'll align the suspension brackets to level, which might give me 1°-2° anti-dive. Meh! It won't kill me.

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: April 4, 2021, 7:32 am 
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OH NO! You've ruined it!
(Just kidding)
Hooray for lowered expectations!

Think about the tools and production build quality of the 60s and 70s.
Remember the bias ply tires? Remember the welding tools for most were stick or gas only?
You can't screw this up by comparison. Everything is in your favor.

Remember the story about the princess and the pea, who had 50 mattresses but could tell if they was a pea in the bottom one?
There are many princesses out there right now, but none on this forum.

Line up your shot and pull the (mig) trigger.
:cheers:

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PostPosted: April 4, 2021, 12:00 pm 
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@MV8

Yes, I'm trying to overcome my perfectionist tendencies, and not "let the perfect be the enemy of the good." I want to drive this bloody thing before I croak.
:zoom:

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: April 4, 2021, 1:41 pm 
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I had a chance to tour the back rooms of a classic car restoration facility. There was a complete body-off restoration of a Ferrari underway, and the bare tube frame was sitting on a stand. The welds were beyond comprehension, looking like a 5-yr old had made them. Big blobs of filler piled up around the joints. Just amazing, but put the body on it and it's a $$$$$$$ Ferrari again...

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PostPosted: April 4, 2021, 2:30 pm 
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Lonnie-S wrote:
I want to drive this bloody thing before I croak.


I've likely/hopefully got another 40 years left, and I've had that same thought many times about mine!

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PostPosted: April 5, 2021, 11:13 am 
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@KB58
No kidding? Were they original welds from the factory?

@Trochu
I know that feeling. The "cure" is spending a whole week working on the build. I always feel hopeful after that. If I've got 6 years left, I'll be surprised. Gotta get that puppy built. :BH:

Cheers all,

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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: April 5, 2021, 12:28 pm 
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Lonnie-S wrote:
@KB58
No kidding? Were they original welds from the factory?


They were most likely factory welds. The Italians were (in)famous for crap welding on their chassis! :shock:

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PostPosted: April 5, 2021, 2:21 pm 
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ngpmike wrote:
Lonnie-S wrote:
@KB58
No kidding? Were they original welds from the factory?


They were most likely factory welds. The Italians were (in)famous for crap welding on their chassis! :shock:



I'll third this one, I worked on a number of vintage Ferraris back in my restoration days, including a '70 312B F1 car... ugly, ugly welds, and equally ugly castings. They did get the job done though, usually.


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PostPosted: April 6, 2021, 8:03 pm 
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OK, I think I've found a solution that works, and satisfies all basic structural and geometry requirements. Although, I feel like a little old bracket maker, I've made so many of these bloody things.
Attachment:
File comment: With some fiddling of the upper brackets, I think I've got a workable solution.
Final Bracket Arrangement.jpg
Final Bracket Arrangement.jpg [ 92.94 KiB | Viewed 549 times ]

The upper brackets are smaller in size, and the bolt holes are different front to back to get the virtual axle to line up with the brackets attached to appropriate chassis members. The rear, upper set with be cantilevered out a little bit, but I'll use a piece of angle iron welded to their backside and the structure to give them support.

So, I set the whole thing up in 3D, did some drawings, and set out to cut the raw brackets from my 2" x 3" stock.
Attachment:
File comment: Shorter rear brackets.
Short Front Rear.jpg
Short Front Rear.jpg [ 54.55 KiB | Viewed 549 times ]

Attachment:
File comment: Taller (bolt hole moved outboard) front bracket.
Tall Front Upper.jpg
Tall Front Upper.jpg [ 52.82 KiB | Viewed 549 times ]


Fortunately, I have enough stock on hand to do more brackets.
Attachment:
File comment: Raw brackets from 2x3x0.125 stock.
Cutting Final Brackets.JPG
Cutting Final Brackets.JPG [ 138.44 KiB | Viewed 549 times ]


Deburred them all and out them in their overnight marinade of white vinegar to get rid of the mill scale. I have 2 spares in case one goes wrong, or I find I need to adjust distances in my real world example.

So, I put them in white vinigar to get rid of the mill scale while I sleep tonight.
Attachment:
File comment: Removing mill scale overnight, prior to finishing.
Overnight Mill Scale Marinade.JPG
Overnight Mill Scale Marinade.JPG [ 145.58 KiB | Viewed 549 times ]


I will have to run the suspension analyzer again with the changed dimensions. That may require a slight raising of the top bracket pairs to keep the roll center about 1" off the pavement.

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: April 9, 2021, 2:35 am 
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Lonnie you're getting closer to rolling that 7 out on the driveway and have all the neighbors come within 6' for a coffee and show 'n tell session :yay: :yay: :yay:
Wish we could be standing on your driveway went that happens :cheers: :cheers: :cheers:

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PostPosted: April 9, 2021, 11:08 am 
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@horchoha

Perry, unless lightning strikes me, I think this thing is going to roll pretty soon.

They're (the Governor & other politicos) talking about having California "back to normal" by Fall. Given I still have to do the steering, fuel and electrical systems (the engine & trans are fitted, but the drive shaft has to be made), it could be you two will be down here by the time it is actually ready to run. That would be great.

They say the Mustang engine will run in a "real stupid" mode if the ECU isn't fully functional, but it is in a real low power, retarded timing state. Not good for driving, but it will do a vroom-vroom kinda thing. :mrgreen:

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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