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Learning how to build Lotus Seven replicas...together!
It is currently December 3, 2023, 12:58 pm

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PostPosted: December 15, 2022, 9:27 pm 
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Joined: May 13, 2009, 6:04 pm
Posts: 163
Location: Missouri
Long over due posting. Hopefully this will inspire some other of our completed builders to start a new topic on what they are doing to enjoy there completed build.

Fully licensed back in the fall of 2017 and doing what it was built for......AutoX. Clean as whistle, no scratches, and the rear fenders hadn't been punished by the cones.
Attachment:
first autox.jpg


Stay tuned for what I've been up to, and if you have a completed build please start a new thread and tell us how you've been enjoying your Locost.


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PostPosted: December 16, 2022, 3:12 pm 
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Joined: April 26, 2008, 6:06 pm
Posts: 3264
Location: Under the weather. (Seattle)
Great work, and glad to see it out in it's natural environment.

Looking forward to the follow-up too.

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie


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PostPosted: December 17, 2022, 2:07 pm 
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Joined: May 13, 2009, 6:04 pm
Posts: 163
Location: Missouri
So what has the car been up to......AutoX, Cars-n-Coffee, and various car show events.

AutoX's have been been a little frustrating up until I got some new tires. The old Bridgeston RE71's had pretty much aged out since I bought them before the car was finished. Yokohama A052 are a good fit for our cars but I'm still giving up a ton of time without the favorite E-Mod or D-Mod tire of choice (Hoosier). The other big struggle is getting the suspension to cooperate. I'm on my second set of springs, which got my ride height where I wanted, but I know I haven't found the optimum alignment and/or settings to maximize my times. I'd also like to experiment with adding a front sway bar since I feel like have to much roll. Just look at this......
Attachment:
roll.jpg
Attachment:
roll1.jpg


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My build http://www.locostusa.com/forums/viewtopic.php?f=35&t=7370


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PostPosted: December 18, 2022, 12:17 pm 
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Joined: October 24, 2008, 2:13 pm
Posts: 5256
Location: Carlsbad, California, USA
Do you have any videos of the car in action? It looks great, by the way.

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: November 8, 2023, 10:57 pm 
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Joined: May 13, 2009, 6:04 pm
Posts: 163
Location: Missouri
Another long overdue update. Figure I'd share my painful experience of upgrading to a 1.8L Miata 7" diff.

Baseline build was centered around the 1.6L open diff. Picked because it came with my donor, it is the lightest option, and research had me convinced that there is no need for limited slip diff. Four years of fighting the dreaded one-wheel-peel coming out of slow corners, banging off the rev-limiter in 2nd gear, or up/down shifting between 2nd/3rd gears during Auto-X, and a buzzy 4K RPM highway drive made me rethink that diff choice.

Enter the solution. I bought a 3.63 Fuji diff with axles that only the Euro/Aussie MX-5's got.

First issue was getting the bigger diff to fit into my chassis. These larger diffs are a simple drop in swap in every Miata assuming you have the correct axles and driveshaft. Not the case when you make a skinny driveshaft tunnel that functions as the Miata PPF. These better diffs extend the driveshaft mating flange (nose) a few inches forward which makes the driveshaft a little shorter. You'll also need the specific flange yoke to mate with the new diff. I also needed to notch some tubing in the driveshaft tunnel, grind on some of the diff casting, and saw off ~0.5" of the diff casting right next to the PPF mounting bolts. Lastly I needed to make a drop out section of my chassis so that I could install/remove the larger diff. Pics to come.
Attachment:
20231202_110751.jpg

Attachment:
1.6diff.jpg

Attachment:
fujidiff.jpg

First few drives were positive. LSD action made acceleration better out of slow corners. Gearing change from 4.3 to 3.63 was a game changer for Auto-X and highway drives. There is a reason why all higher HP Miata folks love the 3.63 and 3.9 diffs. Next few drives the diff started to make angry noises.

After a few weeks of bearing changes, pinion crush sleeve fighting, back lash setting, and multiple bottles of Redline fluid all I successfully did was make different types of diff noises. I pleaded with my driveshaft gut to recheck the balance of my driveshaft, which of course was perfect. We did notice some bluing/wear marks on the driveshaft yoke that goes into the transmission. So one new yoke and one new transmission tailshaft bushing later and guess what the results where? A different noise.

Getting late. Let's finish tomorrow.


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PostPosted: December 2, 2023, 1:43 pm 
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Joined: May 13, 2009, 6:04 pm
Posts: 163
Location: Missouri
Back to the story. Diff/Drivetrain noises. Didn't matter what i did they where always there. Luckily I came across a screaming deal on the favored Miata diff......a 3.9 Torsen diff. This was a known good one, unlike the suspect Fuji diff. Installation went good since I knew where to grind and the axles/driveshaft where interchangeable this they were both the larger 7" diff. Noise situation was greatly reduced for a few months then it reared it ugly head again. Something else had to be at play here. Enter in driveshaft angularity or phasing.
[youtube]https://www.youtube.com/watch?app=desktop&v=Idk3BVDVHq4[/youtube]

Turns out the I had about a 3-degree difference between the front and rear u-joints on the driveshaft. For whatever reason this wasn't an issue with the 1.6 diff, but the bigger Fuji and Torsen diffs resulted on a driveshaft that was a few inches shorter, which apparently was enough to trigger the vibration.

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Last edited by jaf on December 3, 2023, 11:30 am, edited 1 time in total.

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PostPosted: December 3, 2023, 9:30 am 
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You could put a camera behind the pax seat to film any vertical movement at the pinion flange under load, changing the driveshaft angle. Same thing for the trans mount. I don't remember what your mounts look like. I remember the 94-up na diff being less than 7 inch.

Found your build. I see the diff is solid mounted at the front so the only adjustment would be trans mount height. I expect solid mounting the diff would transfer more diff noise.

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PostPosted: December 3, 2023, 11:41 am 
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Joined: May 13, 2009, 6:04 pm
Posts: 163
Location: Missouri
Miatav8,MstrASE,A&P,F wrote:
You could put a camera behind the pax seat to film any vertical movement at the pinion flange under load, changing the driveshaft angle. Same thing for the trans mount. I don't remember what your mounts look like. I remember the 94-up na diff being less than 7 inch.

Found your build. I see the diff is solid mounted at the front so the only adjustment would be trans mount height. I expect solid mounting the diff would transfer more diff noise.


The camera idea crossed by mind numerous times before I found the agularity differences. Funny you talk about the trans mount. I tried shimming it down but all I could bet was 1-degree better, and since the nose of the diff is solid mounted I figured the best method was just to fix it correctly. So off came the diff mounting brackets to re-weld them to make everything correct. If anyone is keeping track the nose of the diff ended up about 0.4" lower to get the 3-degrees out.

Pics of the new mount to get everything lined up properly and the drop-out link to accommodate the larger diff.
Attachment:
20231203_094605.jpg

Attachment:
20231203_094625.jpg


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