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Miata based, scratch built, pseudo street rod
http://locostusa.com/forums/viewtopic.php?f=36&t=17167		 Page 4 of 10
Author:  ThunderHeide [ July 13, 2015, 3:23 pm ]
Post subject:  Re: Miata based, scratch built, pseudo street rod
This is a really unique build, I've always thought about building something similar, definitely gonna follow it!
Author:  mainlandboy [ February 3, 2016, 3:50 am ]
Post subject:  Re: Miata based, scratch built, pseudo street rod
No, I'm not dead, but I took quite a few months off from the project while it was too cold in the unheated barn to work through the winter. Now that it's starting to get a bit warmer, I guess I have no more excuses not to start working on it again.

Here is a picture of the front left lower wishbone, with all of the triangulation stiffening bars added. "Dummy" shock in place for now until I figure out what spring rates to get for the QA1's.
Author:  JackMcCornack [ February 3, 2016, 2:09 pm ]
Post subject:  Re: Miata based, scratch built, pseudo street rod
Welcome back, mainlandboy! Man, I've missed following your build for nigh on six months. Please stick with it and keep us updated; this car is so cool. 8)

And now for some Monday morning quarterbacking: your brace on the LCA takes care of the serious worry (that braking forces would fold the LBJ carrying channel aft, where the big hole is) and the overall coolness of the dropped shock mount made that hole well worth the trouble of external bracing, but I'm puzzled about the placement of that brace.

Was there a wheel (or tire) clearance issue that led you to put the brace tube (the one with the red arrow pointing to it below)...
Attachment:
mainlandboyLCA.jpg
...so far forward? Could the south end of that tube (marked with the green arrow) been attached further south (more toward the rear bushing) without the tire hitting it at full left steering lock?

PS--even if you say, "Yeah, that's a good idea," don't do it! This is a car that should be on the road ASAP.
Author:  mainlandboy [ February 3, 2016, 4:20 pm ]
Post subject:  Re: Miata based, scratch built, pseudo street rod
Hi Jack,

Thanks for your comments! It would have been much easier to place the lower shock mount on top of the LCA like what is done on most Locosts, but that would have forced the upper shock mount to be higher than what looked aesthetically pleasing.

Regarding the placement of the brace you pointed to with the red arrow, your assumption of why it doesn't intersect the main tube further back is exactly correct. The point marked by the green arrow was as far back as this brace could intersect the main LCA tube to allow just enough clearance between the tire and this brace under full steering lock. Wheel offset and width come into play here, so I made sure to have the intended wheels/tires installed before I made this brace.

Cheers,
Mark
Author:  KB58 [ February 3, 2016, 4:28 pm ]
Post subject:  Re: Miata based, scratch built, pseudo street rod
Or move the south-end inboard pickup forward so that it's a straight shot by the brace tube. That additional width of the lower A-arm doesn't improve the strength because it'll flex at the green arrow.
Author:  JackMcCornack [ February 4, 2016, 1:13 am ]
Post subject:  Re: Miata based, scratch built, pseudo street rod
mainlandboy wrote:
Got the main frame rails welded up:
Indeed you have. I'm wondering what tubes (dimensions and wall thickness) you've used on this chassis. And have you put the chassis on the scale yet? I don't want to slow down your build by asking too many questions, but inquiring minds want to know...
Author:  Miatav8,MstrASE,A&P,F [ February 4, 2016, 9:41 am ]
Post subject:  Re: Miata based, scratch built, pseudo street rod
It is tough to build an lca as good as the oem when trying to duplicate the oem attachments for interchangeability.
There are several companies making them for miatas but they are not nearly as light as the oem arms.
Author:  JackMcCornack [ February 4, 2016, 1:15 pm ]
Post subject:  Re: Miata based, scratch built, pseudo street rod
:) Ain't that the truth, Mv8. Particularly for Miatas, which adjut their alignment via moving the lca chassis attachment bushings with eccentric bolt thingies.
Author:  mainlandboy [ February 4, 2016, 5:03 pm ]
Post subject:  Re: Miata based, scratch built, pseudo street rod
KB58 wrote:
Or move the south-end inboard pickup forward so that it's a straight shot by the brace tube. That additional width of the lower A-arm doesn't improve the strength because it'll flex at the green arrow.


The potential issue with this is that because of the flex (although small) in the suspension bushings, moving the lower inboard pickup points closer together will increase the fore/aft movement at the wheel under braking, even if the LCA is super stiff:

Image

If the lower inboard pickup points are too close together, an additional strut brace would be needed anyway, as is the case in some production cars that have an additional link connecting the outer end of the LCA forward to the body to prevent fore/aft movement of the LCA.

Mark
Author:  mainlandboy [ February 4, 2016, 5:05 pm ]
Post subject:  Re: Miata based, scratch built, pseudo street rod
JackMcCornack wrote:
mainlandboy wrote:
Got the main frame rails welded up:
Indeed you have. I'm wondering what tubes (dimensions and wall thickness) you've used on this chassis. And have you put the chassis on the scale yet? I don't want to slow down your build by asking too many questions, but inquiring minds want to know...


Hi Jack, the frame rails (including the kicked up section in the back) are made from 2 X 3 X 1/8 wall ERW. This car is going to be a bit of a porker compared to my Locost, but that's okay. This car serves a different purpose.
Author:  JackMcCornack [ February 5, 2016, 12:11 am ]
Post subject:  Re: Miata based, scratch built, pseudo street rod
Thanks for the info. That's pretty much the traditional modern hod rod chassis stuff; I was wondering if you'd maybe figured the car would be enough lighter with the Miata driveline than the 'Murrican V8 to go for 14 or 12 gauge (.083 or .109) instead of 11 gauge (.125). And I hear you the different purpose; it's sure no further off the beaten Locost track than, say, me getting into ultramilage.

Man, I'm sure glad you're logging your build here so I don't have to check out HAMB every day.
Author:  mainlandboy [ February 13, 2016, 8:42 pm ]
Post subject:  Re: Miata based, scratch built, pseudo street rod
I temporarily attached some cardboard pieces to the side of the chassis to get an idea of how the body will look. Note the ornate Sharpie marker door handle. :)
Author:  Royce [ February 13, 2016, 9:48 pm ]
Post subject:  Re: Miata based, scratch built, pseudo street rod
That is going to be terrific!
Author:  ccrunner [ February 14, 2016, 10:19 am ]
Post subject:  Re: Miata based, scratch built, pseudo street rod
I'm only checking in to say that I'm enjoying following this build, and it's nice that you're back to posting on it.. I'm with you on working in the cold; not fun :shock:

Also wanted to say thanks for taking the time to post part numbers and where you sourced them... makes it super easy for the next guy that needs that bit to go hunt it down..

Keep at it.. you build at a brisk pace, and it's fun to watch your progress :cheers:


--ccrunner
Author:  JackMcCornack [ February 14, 2016, 10:37 am ]
Post subject:  Re: Miata based, scratch built, pseudo street rod
I like how you frenched the door handles. Very smooth.

mainlandboy, I PMed and emailed you a couple questions, but other folks here who are considering using Miata rear subframes may be curious too, so here they are again:

There are two rows of three bolts holding the Miata rear subframe to the chassis. How far apart are those rows (the right row and the left row) from each other? Also, how far are the forward holes of those rows forward from the axle? And how far are the front hole from the back holes? And while we're at it, how high is the top of the subframe (where it bolts to your chassis) from the bottom of your chassis?

I'm not home right now or I'd measure one myself.

I'm loving your build. Your willingness to start afresh on the chassis was brilliant.

Regards, Jack
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