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The Honda diff sure looks easier to mount than the Miata diff. Pardon my fuzzy brain (I hope my brain is wearing out rather than rusting out, but fuzzy is fuzzy regardless of cause) but do you have a build log for your previous car that shows details of your Miata rear end solutions?

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Locost builder and adventurer, and founder (but no longer owner) of Kinetic Vehicles

Jack-
I don't have a build log for the Miata Locost but I can add some photos of the differential mount. The Miata is more difficult because of the long mount ears on top. I tried to design a mount which was removable on the right side so it's platform could be unbolted and the differential removed straight upward for maintenance or repair. I'm not sure I accomplished much since you still have to remove the gas tank first. Anyway here is my design solution right or wrong!

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Build log http://www.locostusa.com/forums/viewtopic.php?t=16510

Both the front and rear knuckles from the S2000 have pressed in ball joints which I will attempt to use. What I now need to do is design and fabricate some ball joint female pieces for the rear bottom and the front bottom A arms to accept these ball joints. All the ball joints have a 7 degree taper. I picked up a tapered reamer for the Miata Locost so I could modify some of the ears. Luckily all the ball joints on the S2000 are also 7 degree tapers.

I started out by measuring the small end and the large end of the tapered ball joint stem. I came up with two possible designs for the female ends. One possible design would use a small box section made up of 1/8" plate separated by the appropriate distance. The two 1/8" plates would be drilled and tapered to match the large and small end of the stem. This worked as shown in the photo but I felt there could be an easier way. I picked up some heavy wall 1" DOM tubing in which the ID closely matched the small end of the appropriate ball joints. I then cut off the appropriate length of tube section and welded it to a square piece of 1/8" tubing that had already been drilled with the same size as the tube ID. I then reamed out the inner diameter using the 7 degree reamer being careful not to take too much off. This gave a nice tapered fit and could be welded and fit to the end of the A arm tubing.

Of course all of this could be avoided by going to a machine shop and have them machine and ream a solid piece of square stock to match the ball joint. Ah but this is too much fun fabricating in your own garage with a small bench top drill press! It would be nice to have a milling machine though.

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Build log http://www.locostusa.com/forums/viewtopic.php?t=16510

I keep forgetting to update this build log.

I started looking at the fuel tank fabrication. Because of the differential mounting configuration a wide (and not too deep) tank is suggested. I started to sketch out the tank but then realized the fuel pump is too deep for my initial layout. See photo of pump.

Since the pump is really a combined unit of pump, filter, return pressure regulator and level indicator it is not easily shortened as can be done with a stock Miata pump unit. So I'm now looking at the design of a sump section at one end of the tank which can handle the extra height of the pump unit. The sump is the obvious choice to also prevent starvation from sloshing during hard turns. I've been reading some of the other posts recently that discuss tank design and they have been helpful. Again, I'm thinking of making the tank from aluminum sheet of a thickness to be determined. The welding is a little more rigorous with TIG but not too difficult.

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Build log http://www.locostusa.com/forums/viewtopic.php?t=16510

I've finished the preliminary design and fabrication of the rear suspension components. The S2000 rear uprights use the typical upper A arm and lower A arm but also have a fifth arm along side the lower A arm that gives the unit adjustability.

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Build log http://www.locostusa.com/forums/viewtopic.php?t=16510

I've also finished the preliminary front suspension design and fabrication. I used the adjustable height upper A arm design originally suggested by McSorley on his web site. This would give additional adjustability to the configuration. To accommodate the full up position of the upper A arm and also the full down position of the A arm either the height of the steering rack must be adjustable or the position of the steering tie rod must be adjustable. I chose to use an adjustable tie rod adapter stud as shown in the photos. I made up spacers for the stud that allow the rod end to be raised of lowered on the stud depending on where the upper A arm is positioned. All this adjustability is to minimize any "bump steer".

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Build log http://www.locostusa.com/forums/viewtopic.php?t=16510

I'm liking your adjustable upper arms, Roy. Can you put up another photo or two of the backside of the mounts? Did you do the slots by hand or do you have a mill? I was going to look at some of the NASCAR-type solutions in detail (slugs, adjustable mounts, etc.) and your's definitely seems to be circle track at least, which appeals to me also because the parts are strong, simple and cheap plus always adjustable.

I haven't done my front end yet, but have a taller spindles/ball joint setup that most of the Locost donors of old. My thinking was doing my lowers as you have done (not on top of the lower rails, but welded to their side) could be the solution to getting more height out of the basic design. Good going! More suspension "porno" I love it.

Cheers,

Lonnie

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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

Lonnie-
I used this adjustable concept on my Miata Locost earlier and hand made the boxes based on photos from McSorley's site. Here's a link:

http://sevenesque.com/assembly/37-upper-control-arms.html

Jim has also got a video that describes his thinking. You don't need to build the boxes as I found out, since Southwest Speed sells them. See McSorley's site for part numbers or I can provide them. Speedway sells the main shaft for the adjustable A arm (part number 910-34362). Speedway also carries the tie rod adapter studs (Part #936-36055).

Roy

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Build log http://www.locostusa.com/forums/viewtopic.php?t=16510

Thank you, Roy. I'll check out the McSorely site.

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

It looks like you put a longer toe arm than stock which is good. The stock arm gives bump steer (toe in) when you lower the car too much because it's not mounted in the proper plane of the upper and lower A arm pivot points.

BUT one thing I've been thinking of doing to completely eliminate that on my S2000 car is to make a mounting point on the lower arm itself.

I'm not sure how you'd implement it on your car, but it's something to think about.

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mobilito ergo sum
I drive therefore I am

I can explain it to you,
but I can't understand it for you.

Thanks for the comment. I tried to match pretty closely the stock Honda rear suspension design, figuring their engineers must know something. I checked the full up and down travel on the current configuration and didn't notice any measurable toe-in or toe-out. I'll check it again when I do a semi-final alignment check. If I remember from the shop manual the S2000 folks do have some toe-in for the rear alignment, not that that will be my final setup.

On the subject of suspension, I still need to decide what to do about the rear and front sway bars. I'm sure the stock S2000 bars are way too large in diameter for such a light car. This will take some further thought. Any suggestions?

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Build log http://www.locostusa.com/forums/viewtopic.php?t=16510

Now that I think about it the stock S2000 rear toe link must give toe out not toe in because we always have to put some toe in to to compensate.

This is the biggest difference in driving an S vs. a Miata, the slight rear instability under a load or on lowered cars. I have both cars and the S is light years better than the Miata in every area except this. Once I have the time to build a rear bracket to correct this it will be the perfect store bought car, well except for the fact that you always want more power from every car you've got.

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mobilito ergo sum
I drive therefore I am

I can explain it to you,
but I can't understand it for you.

I went ahead and shortened the Miata steering rack to accommodate the front end suspension configuration. I had a local machine shop cut off 6 inches of the rack shaft and machine new threads and cut outs. I cut the rack cylinder, removed 6 inches from the approximate center and welded the two halves together. Before cutting the shaft I removed the piston rings. I also realized that I needed to remove the seal from inside the aluminum end cap since this seal would rub on the grooves left on the shaft.

See the two attached photos.

Moving on next to the fuel tank fabrication.

Cheers,
Roy

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Build log http://www.locostusa.com/forums/viewtopic.php?t=16510

Super Noob question but, when shortening the rack like that and making it a manual rack. Will any fluid need to be used? Id imagine some would help just for lubrication.

Look forward to seeing the rest of your build.

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30 years old, not sure what I want to be when I grow up…

Joshua-
On my first build I also de-powered a Miata rack. I packed the rack area and pinion with grease and also greased the shaft surface. The only reason I didn't use the S2000 rack was because it is motor operated and really can't be shortened. I will plug the hydraulic openings with silicon sealer to keep out any dust or dirt.

Roy

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Build log http://www.locostusa.com/forums/viewtopic.php?t=16510