| THE MG |
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 | |  | January 9, 2009 - Here's a rough approximation of how the upper mount will be supported.
A section of the same 2"x3" square tube that makes up the chassis rails will go up and out, and extend beyond the upper arm mounting to provide the upper shock mounting location. Some fore/aft bracing will be added later, and I'll run something from side to side at the top if the engine allows. The base of the bar will also move closer to the center of the frame rail, this is mostly just a convenient place to sit it right now.
I could mount the bar like this, with the upper arm mounting tube welded to the side of the bar. That gives a slightly better location for the shock mount.
Another option would be to angle the bar more and run the tube through the center of the bar. That would be stronger for the tube, but less ideal for the shock mount. Since the shock mount is going to get big loads (the vertical loads from the car go through it while the upper arm mostly has to deal with some side loads and a forward load on braking), I'm thinking the first option might work better.
I'm starting to wonder if I'm going the wrong way here. Should I have the frame rails kick upwards after the firewall, supporting the lower control arm mounting points with a crossmember that dips down under the engine? I'm worried about twisting loads coming from that upper shock mount located so far away from the rail. I could tie into the body, but there's not really much there. Then again, the Miata doesn't have a whole lot of metal in that area and there are no side loads on the shock due to the double wishbone configuration. Meanwhile, the lower control arms take the brunt of the cornering loads from what I understand. Hmm.
entry 133 - tags: suspension, frame | | | January 9, 2009 - While looking around to examine various frame designs, I came across this ambitious project.
A Miata stuffed inside an Morris Minor. I've seen it in the past but had forgotten about it. And check it out, there's the same suspension setup I'm working on. No pictures of the final product which is a shame, but there are some good ideas in there. I like the wood mockup.
entry 134 - tags: suspension, frame | | | January 10, 2009 - Okay, I think I have it.
The crossmember to mount the steering rack actually has to go directly in line with the front lower control arm mounts. I can use a plate or some bars to triangulate the upper mount points to this, getting rid of my twisting problem. It's still a ladder frame with the torsion problems that implies, but a full space frame isn't going to happen at the front of this car.
I'm going to keep thinking about this, both how to implement with the lower control arms as-is and how to deal with the upper location, but I think I'm on the right track.
entry 135 - tags: suspension, frame | | |  | January 11, 2009 - Ooo, a naked MG!
This is from the very cool British Heritage website. From this and other pictures, I have a better idea of where the various beams and strong points are to be found in the body shell. For example, there's a beam at the top of the fender that I'd never noticed before.
I'm going to triangulate my suspension pickups off them, making a pseudo-spaceframe out of the front end. I have a number of the new tubes figured out, but I won't sort out their final locations until the engine is in place. I suspect a few of them will have to be removable as well to deal with engine serviceability.
One thing that occurred to me yesterday is that the high frame rails with a dropped crossmember for mounting the lower control arms won't work with Miata geometry. The front and rear pickup points are a long way apart, and the crossmember for the rear one would go right through the oil pan. That's not good.
entry 136 - tags: suspension, frame | | |  | January 11, 2009 - It doesn't look like much after all that work.
Still, here's the first corner of the new frame. When I look at it in the car, I realize how short many of these distances really are. Most of the length of this bar will be welded to the bottom of the car, both to the floorboard and tied into the existing frame rail. It's not going to be difficult to make everything stiff and solid. I spent most of my working time today finishing some of the design work in my head, and I'm pretty happy with it all. This is just a skeleton.
You can barely see it in the picture, but the upright is welded to the front suspension pickup. I'll add in an extra triangle to help spread the forces around as well as tie into the crossmember that will support the steering rack. The upper end will be tied into the top of the fender and the beam in there, as well as back to the firewall on a bit of an angle. I'm also planning a little more bracing to tie the upper control arm mount to the upright a bit more - nothing complex.
The one mistake I made was that I didn't cap off the end of the upright, and it's going to be tough to do now. I don't really want to leave it open to the elements either. Whoops. It's possible to do, but it will be awkward. Then again, there's no chance of water getting trapped in there now! Is it better to make it watertight (hopefully!) or to make it irrelevant if water gets inside?
entry 137 - tags: suspension, frame | | |  | January 14, 2009 - I picked up a spare speedometer on eBay.
The plan is to stuff electronic guts inside the stock gauge, and I figured having an extra would make me more comfortable taking it apart. I'd rather not go to a $300 adapter or use Autometer gauges, I like the old Smiths look. Besides, it was cheap!
entry 138 - tags: interior, gauges | | |  | January 14, 2009 - It's time to put some suspension on the car.
First, I need to identify exactly where the wheel will go. The centerline was marked with the plumb line. Then I took a measurement from here to the crossmember under the car, where my new frame rails will terminate. As do the originals.
entry 139 - tags: suspension, frame | | |  | January 14, 2009 - In order to fit the new frame rail to the bottom of the car, it has to be cut to match the contours of the floorpan.
There are enough little dips and lips to make this a real pain in the butt, actually. Lots of careful measuring and turning parts around in my head, then it was time to cut.
entry 140 - tags: suspension, frame | | |  | January 14, 2009 - All that careful measuring, and I cut with a Sawzall.
Actually, it's possible to be pretty accurate with one. Check out how straight that edge is! I can't do that well with a bandsaw.
entry 141 - tags: suspension, frame | | |  | January 14, 2009 - Before I could attach anything, I had to clean off the frame rails.
That's some good looking metal for a 37-year-old British car! I used a wire wheel on my angle grinder to clean it up. Really, I don't need to clean up the side of the original frame rail as I can't weld to there, only the edge.
entry 142 - tags: suspension, rust, frame | | |  | January 14, 2009 - After innumerable test fits, small tweaks and a wholesale chop of a 3/4" strip down one side, the suspension is ready to weld in.
Note how the upright goes right into the front fender. It lines up nicely with the support behind the fender. So that's good!
You can see the angle level I'm using to make sure everything is correct. After all that test fitting, I still ended up with a surprising gap between the top of the rail and the floorboard. I'll fix that either with a piece of small angle welded in (which will actually provide a little more stiffness, I think) or by persuading the thin floor to move slightly. It's not far off, but it doesn't take much for a weld to be a problem. I'm also probably going to have to see if I can remove the asphalt sound deadening from the floorboards. Now that is going to be a pain.
Everything's just welded enough to hold it in place, although I can't call some of those welds under the car tack welds. They're pretty beefy. The ones at the top of the upright are tacks, though.
entry 143 - tags: suspension, frame | | |  | January 14, 2009 - So, how did the wheel align after all that?
Almost perfectly. It looks like it's moved forward slightly from my ideal, but not enough that anyone will ever notice. The only problem is that according to my angle level, I don't have much negative camber. I think I'll move the top of my upright inboard just slightly, enough to move the adjustment range more into the negative range. Before doing that, though, I'm going to measure it again tomorrow. I should tighten all the suspension bolts more first to make sure I'm getting accurate readings, they're all just finger tight right now.
The suspension has lots of room to move and it's all nicely fixed to the car. Some extra braces will be coming to reinforce the upright, but this is enough to get me started.
Now I just do the same (only faster!) on the other side of the car, then put the crossmembers in. And with that, I can start to figure motor mounts, steering column routing, wheel flares and a bunch of other items. Here we go!
entry 144 - tags: suspension, frame | | |  | January 16, 2009 - Yuk.
I'm removing the asphalt sound deadening from the floorboards so I don't set it on fire while welding to the floor. It's coming off fairly well with a hammer and chisel, so I'm going to pick up an air hammer on the way home from work today to expedite matters. Then the condition of the floorboards will be revealed, but nothing I've seen so far leads me to be concerned. It looks bad in pictures, but all the rust is just surface scum. I can't believe I got so lucky!
entry 145 - tags: interior, rust | | |  | January 17, 2009 - I've been given varying advice on how best to remove the asphalt.
Freeze it with dry ice so it shatters, warm it with a heat gun and use a putty knife, and melt it off with various chemical cocktails. I stuck by my original plan and picked up a $4.50 air hammer from Harbor Freight. It was the perfect tool for the job, ripping out the stuff in no time flat. This picture was taken partway through the work.
entry 146 - tags: floor, sound deadening, tools | | |  | January 17, 2009 - Unfortunately, the car was not completely rust-free.
Even before all of the asphalt was up, this section came to light. There's a hole in the top of the sill as well as this damage to the floorboard at the base of the sill. Not too much, though, and it's restricted to the area that can be seen here. It's an easy patch job, no need to bother with new panels. I'll probably cut out the floor between the sill and the raised bit, then put an L-shaped piece of steel in to tie them together.
With the rest of the floors cleaned off on both sides of the car, this was it for rust. Everything else looked just fine. There's still asphalt on the raised ribs on the floor in this picture though, and that makes it look a little dodgy.
entry 147 - tags: rust, floors, asphalt | | |  | January 18, 2009 - It was too nice a day outside to work much on the MG.
But I did get the left front suspension started. Here it is in the highly professional jig for the upper control arm placement.
I assure you, the welds look much less dodgy in person!
entry 148 - tags: suspension | | |  | January 19, 2009 - See?
Not so bad.
entry 149 - tags: suspension | | |  | January 19, 2009 - The left front suspension is all together.
So tomorrow it'll get welded to the car. Then the steering rack support - and then I'll be able to steer the wheels! How exciting.
entry 150 - tags: suspension | | | January 20, 2009 - Whoops.
I got the second frame rail cut to shape and tack-welded into place. Then, just to check my placement, I checked the horizontal distance between the front control arm mounting points.
They were about 10mm too wide.
That's odd, how could I have made that miscalculation? Just for fun, I checked the distance between the rails at the front. Again, about 10mm too wide. But the rails were pushed up tight against the inside of the stock rails, so how could that have happened? A bit of head scratching and then I checked the width of the rails at the firewall. Perfect.
They're splayed.
So I crawled back under the car again to see if one wasn't butted tight against the stock rail, but both were good. Sighting along the new rail showed me the problem, though. The rails weren't straight. In my excitement to put the suspension pickups in place, I'd managed to warp them. Obvious in retrospect, not something I expected at the time. At least it appears I did it nice and evenly, but this isn't good.
So I think I'll try heating up the inside edge of the rails and see if they pull back straight. It's a trick I learned from an exhaust shop - heat up the steel and let it cool, and the hot side will shrink down a bit. Basically, do the same thing that bent them in the first place. Either that or I cut them loose and start over, or cut and weld the rails with an angle correction. Ugh. I'll try heat first.
entry 151 - tags: suspension, frame, ok | | | January 21, 2009 - Some more thinking on the frame rails.
I'm going to replace them, and I'll take the opportunity to bump the wall thickness a bit. Just because. The mounts will get cut off the existing rails and welded on. I know how I can do this without needing to go through all the fixturing again.
This is the smart choice. I was trying to think of easier ways, but it'll only be another couple of hours worth of work, and it's the strongest and best solution.
entry 152 - tags: suspension, frame | | |
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