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PostPosted: Mon Nov 04, 2013 2:17 am 
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Joined: Fri Apr 17, 2009 1:28 am
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Location: Queen Creek, Arizona
Well, I guess it is time for me to start a build log and join in on the madness.

In August, I picked up a well traveled, but stalled, project.
It is a book chassis with Miata running gear and suspension.

The poor thing had been out in the weather for some time, and suffering from a severe case of oxidation. I have spent a bit of time removing a good portion of the rust, but still need to strip it down to get to the rest. In addition to the cleanup effort, I have been tightening things up a bit, replacing odd bolts with a more correct fitment.

I will be posting pics later.
In the mean time, I do have some observations:

1. The engine is soft mounted.

2. Transmission and differential appear to be hard mounted.
--Is the machined surface (with two 10mm(?) threaded holes) on the bottom of the tail housing,
just ahead of the gear selector, strong enough to use as a soft mount point?

3. Ride height with the 14" wheels currently fitted is about 4.5".
--I think 15" wheels (at least) will fix #3 & 4

4. The pan sits about 1.75" below the frame, giving 2.75" clearance. That should be OK in the
garage, but out on the street -- maybe a little low.


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PostPosted: Mon Nov 04, 2013 12:58 pm 
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Location: Victoria, BC
Hi Walt. Nice to see another Miata build taking place. That's what I'm doing as well though it sounds like you have a head start now. Looking forward to pics.

Marcel

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PostPosted: Tue Nov 05, 2013 12:09 am 
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Location: Queen Creek, Arizona
Well, I promised photos, so here are a couple to start out.
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PostPosted: Tue Nov 05, 2013 12:36 am 
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Location: Queen Creek, Arizona
O.K., I think that went well. Now for a few more:
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The trip to the local machine shop was a worthwhile venture. Where there had been an obstruction allowing only 1" of thread engagement of the upper ball joint, now it will thread all the way in (more than I need)

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Although the stock headers seem to work here, I may opt to try my hand at some fab work down the time-line a bit


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PostPosted: Wed Nov 06, 2013 10:55 am 
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Location: worcester county, Massachsetts
waltj wrote:
Well, I guess it is time for me to start a build log and join in on the madness.

In August, I picked up a well traveled, but stalled, project.
It is a book chassis with Miata running gear and suspension.


nice! And, Welcome!

Quote:
1. The engine is soft mounted.

2. Transmission and differential appear to be hard mounted.
--Is the machined surface (with two 10mm(?) threaded holes) on the bottom of the tail housing,
just ahead of the gear selector, strong enough to use as a soft mount point?


it has been noted hereabouts before that all three mounting points of the engine trannt subassy should either all be solid mount, or all be soft mount. I'm sure others will chime in, but the concensus I have read in differnt builds has been to design a soft tailshaft mount that uses the original mounts for the Miata torque arm which connects the transmission tailshaft to the differential housing.

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PostPosted: Wed Nov 06, 2013 1:48 pm 
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Always Moore!
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Location: Pittsburgh, PA
To add to that, there have been several builders that have had Miata differential snout mounts fail when they are hard mounted. You'll want to either install a bushing on the front and keep the stock bushings on the ears or hard mount all three points.

The harder the mount, the more load it will carry. If you have two soft mounts and one hard mount, the hard mount will carry most of the load. Not to say there isn't significant load at the engine and transmission mounts but the torque trying to move the front of the differential will be 4.1 times what it is at the back of the transmission and this is before you start worrying about drivetrain shock loads.

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PostPosted: Wed Nov 06, 2013 10:28 pm 
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Location: Queen Creek, Arizona
robbovius and a.moore, thanks for dropping by.

I know that I must at least match the mounts on the engine and trans, which I intend to do. The question I did have about the Miata trans is that in the Miata, it hangs onto the PPF at the side mounting point, and there is, what appears to be, another mount point under the tail housing (like most transmissions). This is a machined surface with 2 threaded holes (for 10 mm bolt) spaced at about 32 - 33 mm apart. I am guessing at that measurement and can't check at the moment. The question is, would the tail housing handle using that as the rear, third mount for the engine/transmission combo?

This would simplify things if it will support the task.

I would like to soft mount the diff. but I think that will require some serious rework + replacements for the missing pieces.
I think the diff needs a little nudge any way, because, as close as I can measure, the drive line is currently as straight as an arrow. That may not be real good for the drive shaft components.

Walt


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PostPosted: Wed Nov 06, 2013 10:33 pm 
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Always Moore!
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Location: Pittsburgh, PA
The NC transmission has something similar on the bottom and a beefy PPF mount on the left side. I used the lower mount for mine and after 4,000 miles it has been fine: download/file.php?id=15687

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PostPosted: Mon Dec 02, 2013 12:05 am 
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Location: Queen Creek, Arizona
Between waiting for solutions to come into view and then the parts to arrive, there has been only minor progress. It seems like one step forward is followed by two steps back and if that keeps up, I'll be looking at a bundle of steel on the garage floor.

The diff is now mounted using Energy Suspension mounts bushings at the rear, but still needs the nose to be supported in some manner. I'm still thinking on that.

The transmission hard mount is disconnected, and the parts are fabricated to support the tail of the transmission using the mount point at the rear of the transmission. There are, however, clearance issues with the “B2” frame piece and the floor in the tunnel. There appear to be two possible solutions:

1. Remove / relocate the tunnel portion of “B2” (an inch forward would work).

2. Move the engine to the left about ½” and back 1 ½”. This would help with the
transmission mount clearance issue, and would also give the throttle linkage a little
breathing room.

If the tunnel section of “B2” is moved forward 1”, how will that effect the integrity of the chassis?
Attachment:
File comment: If the flats on the bolt are parallel with the B2 tube, with the longer bolt needed, they touch
locost 049.jpg
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Option 2 is interesting for several reasons. It will resolve the two points mentioned above, and gives the opportunity to reduce the engine exposure below the frame rails and I could do a little upgrade to the motor mounts.
Attachment:
locost 009 a.JPG
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PostPosted: Mon Dec 02, 2013 9:29 am 
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Location: S.E. Michigan
Walt
I would just add a gusset between the two vertical plates on the motor mount, which should stabilize the mount when seeing fore/aft loads. Depending on clearance you may want to put an access hole in the gusset to reach the motor mount nut if the gusset is on the outboard side of the mount. Dave W


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PostPosted: Tue Mar 25, 2014 12:15 am 
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Joined: Fri Apr 17, 2009 1:28 am
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Location: Queen Creek, Arizona
Well, it has been a while since I last posted on progress. I have not been totally idle, there has been a lot of repositioning, rebuilding and removing going on since December. The front motor mounts had to come out to move the engine back a bit and I found one mount torn (in two pieces). When I set the engine back down, I noticed that there was about a 10*+ difference between the engine plate and the chassis plate, putting undue stress on the mount (Both sides about the same). So, chassis mounts got reset to proper angle. On to the trans mount; as the engine was moved back to allow for a clean location of the rear mount, the "H" verticals at the tunnel entry and the center of "Q" were too close to the trans (they got repositioned). When I set the engine back down, G1 and G2 were the only things keeping it up. Looking at the drawings, seems like they were where they should be at the nose end, but were too far apart at the firewall end. Fixed that by adding G1a and G2a. Added plates to support the reworked motor mounts. Then the trans mount was tacked together.

As soon as my camera battery comes in, I can get the pictures I have out of the camera and post them.

Walt


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PostPosted: Mon Apr 21, 2014 9:28 pm 
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Location: Winter Park / Orlando
Great to see you back at it, Walt! Pictures would be nice to show your progress, so add them when you get your battery back in your camera.

Sometimes you have to ad-lib a bit! I wanted my Miata 1.6 as far back in the frame as possible, so I ad-libbed!
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You can see far back the engine sits:
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My advice is not to worry too much about the drawings...there are endless ways to make it work! My $.02 worth...
Good luck!
-Gar

viewtopic.php?f=35&t=14227&p=179494#p179494


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PostPosted: Mon Apr 21, 2014 9:35 pm 
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Location: Shawnee, Ks
Love your "tie" rod!!!!

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