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PostPosted: Thu Jul 17, 2008 11:16 am 
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Joined: Mon Dec 17, 2007 1:17 pm
Posts: 552
Time to join the masses!

I've been in various stages of building since I bought my donor on Superbowl Sunday, but finally started what I consider the build (the frame) recently.

An overview of the project:

McSorley +442 chasis
Engine/Transmission: 1989 Nissan 240SX (KA24E)
140hp @ 5600rpm
152lbs-ft @ 4400rpm
5 speed manual

Front Suspension:
Uprights, brakes etc from a 1999 Miata. Although I am thinking of doing a swap of the larger '99 brakes onto my '90 Miata and putting the smaller (lighter?) stuff on the Locost to help reduce weight.
Shocks are from a Shelby Series One, and hopefully will be pushrod activated.

Rear:
Still evaluating rear axle options. Definitely going with a solid rear axle (for reasons of reducing complexity). Leading candidate at the moment in from a Volvo. Looking for 3.73 or 4.10 ratio (the 240 was a 4.1 stock). Volvos commonly came with lockers and disc brakes, and are pretty common around these parts.

I was originally planning to use the 240SX for all of the suspension, but the Miata parts came up for sale, and the idea of travelling a well beaten path was hard to resist. The Nissan is also pretty beat, so would need a lot of updating/rebuilding etc.

Steering: Hoping to do a shortened Nissan rack. The 240SX is rear steer, so it wouldn't work, however I picked up a cheap Silvia (Japanese 240SX) rack, which should work (since when you flip it, it will be setup for LHD).

Bodywork: Hoping to do everything but the nose myself, but having never done any fiberglass, we will see.

Anyways, onto the pics:

Donor:
Image

Image

Image

Shocks (we'll see if these work for my application):
Image

Build Table:
Image
This is pretty basic. 1 sheet of 3/4" MDF, with a wood frame. It sits on a set of legs on casters. Reasonably easy (although HEAVY) to move and disassemble.

Flipping the donor:
Image

I'll update with some shots of the frame in progress when I take some pictures. One of the big challenges for me is that the build is taking place at my parent's house, about 45 minutes away, so finding time to work on it is a bit challenging.


Last edited by gtivr4 on Thu Sep 18, 2008 4:29 pm, edited 1 time in total.

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PostPosted: Thu Jul 17, 2008 1:30 pm 
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Since you have it already, have you looked at possibly using the 240 diff and hubs in a Dedion type of setup?

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PostPosted: Thu Jul 17, 2008 1:51 pm 
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Location: Louisville, KY
The 240SX diff is really heavy and pretty bulky.

I think the uprights would lend themselves well to a deDion, but the if it were me, I'd chuck the SX diff and go with a Subaru rear diff.

Or like he said, go with a solid diff because it's easy.


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PostPosted: Thu Jul 17, 2008 2:25 pm 
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Yeah....DeDion. What was I thinkin....all the complexity of IRS with few of the benefits.... :oops:

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PostPosted: Thu Jul 17, 2008 3:31 pm 
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Fester wrote:
The 240SX diff is really heavy and pretty bulky.

Not to mention, mine has seen 170k (northeast) miles, and would need attention. Not to mention, a limited slip.

Let's put it this way, the LSD for the 240 is $450 or so. An entire solid axle, including brakes, locker, correct ratios etc is $250 or so. Combine that with the reduced complexity and I am sold!


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PostPosted: Thu Jul 17, 2008 3:46 pm 
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MustangSix wrote:
Yeah....DeDion. What was I thinkin....all the complexity of IRS with few of the benefits.... :oops:


Actually I think a properly designed DeDion (or something similar in concept anyway) could be made adjustable so static camber and toe can be adjusted - a benefit not so easily achieved with a solid axle, but for the average builder it's a lot easier to go with a solid axle.

gtivr4, did you get to drive the 240SX before parting it out? I had an '89 and contrary to what the SR20DET swappers will tell you, the KA24E does an admirable job of hauling the car around and is adequately willing to rev. I can't imagine how much fun it will be with 1200 pounds less mass to tug around.


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PostPosted: Thu Jul 17, 2008 3:58 pm 
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Fester wrote:
gtivr4, did you get to drive the 240SX before parting it out? I had an '89 and contrary to what the SR20DET swappers will tell you, the KA24E does an admirable job of hauling the car around and is adequately willing to rev. I can't imagine how much fun it will be with 1200 pounds less mass to tug around.


No, and I wish I had. The car was pretty bad. Brakes were totally gone, tires were bald and flat, rust EVERYWHERE. So I drove it maybe 10 feet in the snow (must have been a lot more than that according to the odo given how much wheelspin was involved).

I did get a chance to rev it up a bit, and was surprised at how free revving it is. Especially considering it's truck origins. Should be a blast, and I always like a bit of extra torque!


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 Post subject: Updates!
PostPosted: Tue Sep 02, 2008 10:23 am 
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It's been a productive couple of weekends, with some good progress.

Two weeks ago, I finally bought an axle:

It's from a 1993 Volvo 940.
Specs:
59" (approximate) from WMS to WMS
5x108 bolt pattern
integrated drum emergency brake
Solid rear disc brakes, with (very small) dual piston calipers.
Input is offset just a hair under an inch to the passenger side.

Weight: All up, 175lbs including brakes, fluid, everything. Calipers weigh in around 37 lbs (so axle without disc brakes (but including drum components) and fluid is about 137lbs)

It's a Posi (a locker actually that only locks up to 25mph, but there is a way to make it engage at faster speeds), 4.10 gears. Apparently it's very closely related to a Dana 30 axle, so other LSD units are pretty readily available.

Cost: $200 from a junkyard.

Sorry no images of the axle specifically.


Last edited by gtivr4 on Tue Sep 02, 2008 10:52 am, edited 1 time in total.

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 Post subject: Axle/Engine mockup
PostPosted: Tue Sep 02, 2008 10:36 am 
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Posts: 552
So after buying the axle, it was time for a little test fitting.


Attachments:
File comment: Side view with beefy wood engine mounts!
P1060807.JPG
P1060807.JPG [ 60.17 KiB | Viewed 3767 times ]
File comment: A/C unit will have to go, as it will be in the way of they steering (not that I was planning to use it anyways)
P1060808.JPG
P1060808.JPG [ 50.96 KiB | Viewed 3767 times ]
File comment: Gonna have to remove the fan, it adds about 3" to the front end, and an electric fan on the radiator will be plenty. Steering rack is from a RHD silvia, will need to be cut down.
P1060806.JPG
P1060806.JPG [ 48.1 KiB | Viewed 3764 times ]
File comment: This looks to be about as far back as is realistic to mount things.
P1060804.JPG
P1060804.JPG [ 52.87 KiB | Viewed 3766 times ]
File comment: First engine placement. Offset to right about 1" (to coincide with the offset of the axle).
P1060803.JPG
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File comment: Axle location (just looking around really).
P1060802.JPG
P1060802.JPG [ 47.79 KiB | Viewed 3760 times ]
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 Post subject: More Axle/Engine Mockups
PostPosted: Tue Sep 02, 2008 10:38 am 
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Posts: 552
Some more images for your enjoyment:
Image
The first "driving" photos

Image


Attachments:
File comment: G tube will be in the way of the distributor, so will have to be rethought
P1060811.JPG
P1060811.JPG [ 50.7 KiB | Viewed 3759 times ]


Last edited by gtivr4 on Tue Sep 02, 2008 10:55 am, edited 1 time in total.
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 Post subject: More mockup progress
PostPosted: Tue Sep 02, 2008 10:54 am 
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Posts: 552
A couple more days worth of work. Did a lot of finish welding, but there are still a few pieces to work on in that respect.

Finished the rear end of the frame:

I used Chet's approach to bending the top tube (although I used 1" 16ga tubing). I didn't feel like I could do a good job with the lower corners, so I wimped out and built them out of 3/4" with a 45º angle. Hopefully that will do the trick!


Attachments:
P1060818.JPG
P1060818.JPG [ 57.13 KiB | Viewed 3754 times ]
File comment: It ain't pretty but it worked.
P1060816.JPG
P1060816.JPG [ 27.48 KiB | Viewed 3752 times ]
File comment: Rear end nearing completion
P1060815.JPG
P1060815.JPG [ 59.24 KiB | Viewed 3750 times ]
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 Post subject: Rear Axle Thinking
PostPosted: Sun Sep 28, 2008 8:55 pm 
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So this was a thinking weekend (well just a day really) for me.

Set everything up, and realized that the trailing arms I ordered were 2" too long (my bad!), so that didn't happen.

However, I did draw up some ideas on mounting the shocks to the axle, and would love some feedback in regards to the angle of the shocks, and the mounting bracket.


Attachments:
File comment: Here they are at middle of their travel range (about 2.5" less).
rearshocks_rear_midext.gif
rearshocks_rear_midext.gif [ 5.31 KiB | Viewed 3566 times ]
File comment: Rear view of both shocks and axles with shocks at full extension. Black items are the trailing arm mounts. Shocks are at around 15º (plus the above 10º on the other axis)
rearshocks_rear_fullext.gif
rearshocks_rear_fullext.gif [ 5.47 KiB | Viewed 3567 times ]
File comment: Rear Shock Mounting from the side. Dimensions are approximate. Would this be a strong enough arrangement? The angle of the shock is about 10º.
rearshocks_side.gif
rearshocks_side.gif [ 9.28 KiB | Viewed 3563 times ]
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PostPosted: Sun Sep 28, 2008 9:54 pm 
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I'm not a suspension engineer, but having the shocks angle inward from top to bottom seems like it would give you some awfully strange moments and reactions. I'd shoot to have them either straight up and down, or angle OUTward from top to bottom.

Why are you married to the outboard upper shock locations?
Can you move both shocks inboard a bit?
Can you fit them outboard of the trailing arm mounts?

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PostPosted: Mon Sep 29, 2008 8:39 am 
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I wouldn't worry about interference on full bump on both sides, but see what they will do with frull droop on one side and full bump on the other.

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PostPosted: Mon Sep 29, 2008 9:21 am 
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Location: SoCal
I assume this was done to clear something or lower installation ratio because they're bike shocks - I haven't read the entire thread.

The setup is falling-rate, but not terribly. If you can get the shocks upright, preferably by moving the bottoms out, that would be better. Moving either top or bottom inboard lowers your installation ratio, meaning stronger springs are needed than perhaps was expected.

Have you done the math to calculate installation ratio and desired wheel rate? I'm suspicious that bike shocks can have decent wheel travel AND proper wheel rate. I had some R6 shocks, 2" travel and 600 lb springs. Your installation ratio appears to be about 1/2, so you'll have 4" of travel - on one-wheel bumps only! - and a wheel rate of 150 lbs. Is that what you had in mind.

Note that if you hit a dip that runs across the road, both springs compress, resulting in only 2" of total suspension travel... especially bad considering that they're already compressed about 50% in normal ride height. 0.75" compression when hitting a bump is bad. Worse, the 2" total shock travel is with no bump rubber so somethings needed which'll decrease it further.

Sorry to rain on the parade but it's kind of important. If a dip is hit mid-turn the car will oversteer and spin off the road - unless crazy-stiff springs are used to prevent suspension movement.

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