Mini ST Hotrod

[MiniDave]

With a decent start on the front of the car, it's time to switch things up and do some engineering on the back end....to that end I ordered the back half of a "Midi" kit from MiniTec, I had full intended to weld all this up my self but I figured why reinvent the wheel. It was spendy but it solves a lot of issues. Off course it opens the door to just as many since their kit is for putting Honda motors in and I'm doing a Ford.

The parts arrived today and I spent some time familiarizing myself with the various components, then went ahead and assembled the basic framework.

Next I'll take it all apart again and start figuring out how to mount the motor.....

[MiniDave]

Mocking up the motor in the subframe, a couple of interesting issues have come up.....

Looking at the Honda powered version my friend Russ built, the bottom of his crankcase is level with the bottom of the subframe - a good idea so you don't drag the crankcase on anything.....to achieve that is fairly easy, but there are some knock-on problems. Looking down from the top you can see that the axles will have an angle to get to the control arms, so I need to move the frame as far back as possible to minimize it, that puts the top bar of the frame almost against the intake manifold. Moving the engine further forward isn't possible.....

So, I need to find out what the acceptable amount of angle is......I seem to recall that Binky's front axles run at an angle too.

The second issue is that there is limited upward travel on the control arms, moving the frame down (engine up) means almost zero vertical travel available at the control arms, which would mean a terrible ride - plenty of room for the arms to drop but almost no room to go up on a bump.

Dropping the engine lower fixes that, but them the crankcase is more exposed and the frame moves forward again, increasing the axle's angle both forward and vertically. I could lengthen the trailing arms, but that moves the wheels back further in the wheel openings.....the big flares would cover that except there may not be enough room at the back of the wheel wells. Everything I do only seems to make the axle angles worse, so this will be a head scratcher.

So far I haven't even begun to figure out motor mounts.....I think I'll probably order a cheap set of factory mounts and see if I can build something from them.

I'll get some pics up later to show what I mean

[MiniDave]

This is one of the issues I'm trying to resolve - the grey pipe represents the axle, and as you can see there's quite a bit of angle downward, but also there's a lot of angle forward too. My experience the axle should be as straight as possible when the car is down on its wheels.

I can raise the frame up some to mitigate the downward angle, but that tends to move it more forward, increasing the forward angle.....still studying this for now....

[MiniDave]

I fit up the motor to the subframe and right away several issue were evident - the A/C compressor will NOT fit where it's supposed to, and the axles were at crazy angles to reach the hubs......so I spent several days pondering, moving, adjusting and scratching my head trying to figure out how to make it all work.

I'm still not 100% there, but one question needs to be answered. I always thought the axles should be as straight as possible to the hubs and gearbox under normal ride height - is this correct, or just the preferred situation?

Dan pointed out the crazy angles his VW bus axles run at all the time. First thought is - yeah, but it's a slow moving low HP bus - except it isn't, it's a 150hp bus that he tows a loaded trailer or a Mini behind at 70+ MPH for hundreds of miles at a time, and after 20K miles or so, his axles still seem fine.

I also seem to remember that Project Binky's front axles  run at some angles too?

Point being if I can run some odd angles, I can probably put my A/C compressor back on.

To test out a couple of theories I moved the engine around, tilted it somewhat and built a couple of brackets to set the ride height approximately where I think it will be - at about 1/2 of the shock travel. Doing all that I've managed to get the axles pretty much straight on in both directions. I will have to do some small modifications - I'll need to remove a boss on the oil pan where the A/C compressor used to bolt up, and I will have to completely engineer a bracket to remount the compressor somewhere else......but that at least gets me in the neighborhood.

But, if I can run the angles then I may be able to move the engine back further in the frame set and put the compressor back on.

What say the cognoscenti?

[94touring]

You may need to Google the max angle the CVs allow to see how crazy you can go with the axles.  Lemme see if I can find a pic of mine.

[94touring]

Here's what I found for VWs.  Type 2 bus can have 17 degrees angle. Type 4 CVs can have 22 degrees.

[MiniDave]

I haven't gotten MiniTec to tell me what CV's they run yet......

[MiniDave]

So MiniTec called me back and after a good conversation I now know what to get parts-wise to keep moving forward.

Don dropped by and helped me lift the subframe up and off the engine so I could get it up on my lift table and get started cutting off that boss to make clearance for the suspension arms to move.

Once up on the table it wasn't too hard to cut the boss off and use my angle grinder to clean up the area enough to do a test fit. Putting the subframe back in place by myself turned into a challenge, but using the engine lift and some straps and chains I managed to get it in place.

Now the axles line up nicely and there's room on both ends for the trailing arms to move without hitting anything.

I messaged my brother in England who used to work for Sanden to ask about compressors as I won't be able to use this one now that I'm using the area where it used to mount for the suspension.....he gave me a couple of leads as it's now going to turn the opposite direction - on what compressor to order and it turns out they're readily available and fairly inexpensive. Once I build the motor mounts, add the coilovers and axles, I'll be able to see where exactly I can put it and build some brackets to mount it.

I know on some of the Vtec Mini builds they mount the alternator to the frame rather than the motor - not sure that would work but it's an interesting thought anyway....I'd be concerned with vibration when it's running and how to tension the belt.

1st pic shows where I cut off the boss, second the clearance to the trailing arm and third the nice straight axle lineup.

While I had the subframe standing on its side I also found where the adjustment is for camber, it uses a large eccentric washer to move it where you want it.....simple and effective. A similar set up adjusts toe....

All of the aluminum has a lot of corrosion on it, I found some liquid spray-on stuff that's supposed to clean the corrosion off without damaging the metal......that will be one of the last jobs I do, but I'm definitely going to give it a good shot at cleaning it off. Maybe while the engine's out when the body is at paint would be a good time to tackle that......

[MiniDave]

Trying to sort out how to do the motor mounts, MiniTec sent me a pair of what they use. The transmichigan end is easy - lots of room. The other end is close! I cut a length of 1 1/2" angle and mounted it to see how I can do this - it's possible - it just fits in the gap, but it is tight!

I also ran the suspension to both extremes and everything clears with ease, so no worries there.

[MiniDave]

After finagling the motor around in the frame a bit, I welded up the motor mount on the engine side, ran out of back and material to finish it. Next I'll build the legs that attach it to the subframe, then switch over to the transmission end. I also need to buy some bolts and some more metal for the "legs" on both ends, plus I want to brace up the shell before I start cutting any metal out of it - it's probably only held together with the paint as it is!

This is my first effort and I'm sure I could do better, but as long as it holds, the only one who will ever see it is me!

I had a weird thing happen when I was trying to weld it up - I was just putting a couple of tacks in to see if I had the angle and spacing right, and it just would not weld. I was using a couple of very strong magnets to hold things in place, so I switched over to regular c clamps - it immediately welded up normally! I think I've run into this before, where a magnet somehow screws with the welding arc. At any rate, I'm glad I figured it out cause I was getting pretty frustrated with it!

I'm going to clean up the edges and weld splatter before I'm done with it.

[cstudep]

Looking good Dave!

As far as the welding and magnets goes, I have always heard it referred to as arc blow, no idea if that is what it is officially called or not. The stronger the magnets the more pronounced it can be. You can usually mitigate it by moving the ground clamp around and the closer to the weld the better, also located between the weld and the magnet if at all possible. Obviously once tacked remove the magnets to fully weld. Basically the magnetic field of the magnets is interfering with the magnetic field of the welder.

[MiniDave]

Well, given that the welder I'm using is 35 years old and only a 120V and I'm welding 1/4" metal, I need everything it's got!

I'll just use clamps from here on out, cause I'm getting good penetration and nice smooth welds now.

Can't decide if I need to gusset the sides of that mount now or not.....I think it's plenty as is, but I might go all out and fill it in.

[94touring]

I'd gusset it myself

[MiniDave]

Yeah, I'm thinking the same way......I found a metal store that's not halfway to St. Louis like the one I used to use, and they have pretty much everything! They're in Olathe which is only about a 10 minute drive instead of 1/2 hour or more......prices are double what they were a few years ago, but I got everything I need for now....

[MiniDave]

So I picked up a load of metal - it only came to a little over $100 - and that should allow me to do all the bracing of the shell, finish the motor mounts and a few other mods....

I've been getting the rear hubs all figured out - I bought the hub and disc rotors, pressed the hub into the rear bearing and found that my standard offset wheels rub the trailing arm. I also decided to change out the studs so I don't have to carry metric nuts and English ones both. I can always just use a spacer, or If I'm having Force Racing build me some custom wheels they can change the offset for me.

Clancy uses 7/16" studs instead of the 3/8" that come in the Sprite/Mini hubs, however the rear hubs are for a Miata, and use 10mm studs - which is slightly bigger than 7/16". In fact, the 7/16" studs just dropped into the holes......also the spacing is just very slightly wrong, so as you tighten the lugs you slightly bend your studs. To fix both of these problems, Clancy loaned me a fixture he uses when he drills out the hubs, I put the new, slightly smaller diameter 7/16" studs into the holes and bolted them to the fixture - that pulled them straight and there was just enough play in the holes that the studs came out straight too. Then I welded them to the hub. I just tried them in the wheel and they pull up nice and true....

Next I'll press out the 3/8"studs from the Mini front hubs, drill the holes out and press in the 7/16" studs....since those holes will be the right size I won't have to weld them, the splines will hold just fine. 7/16" studs will torque at 70-80 ft lbs too (compared to standard Mini studs at 45 ft lbs), which I think will be a good idea considering the extra HP and sticky tires I plan to run

The reason I'm focusing on these rear hubs is once I have the motor mounts finished up then I can measure the length of the axles I'll need and get the shop started on them......no telling how long it will take them to make them but judging on their past performance I'm expecting it to take a couple of months!

[MiniDave]

Built the motor mount for the transmission end today, next I'll build the connections to the gearbox.....then do the same on the other end.

Once that's done I'll need to build a bracket to keep the engine from rocking - I've got a couple of good ideas but haven't finalized any plans yet.

[94touring]

That one looks solid

[MiniDave]

I'm probably going to redo the other one, I'm not completely happy with it.....

Ran out of welding wire, I usually just buy it from Harbor Freight, but they didn't have any of the 2 lb .023 spools I usually buy, nor did I see any of the 11lb spools either. I asked at the desk and they found  a lone 11 lb spool " in back" that I think had been on the shelf a long time, based on the amount of dust on it, so they gave me 20% off. It's .025 which actually worked a little better on this 1/4" thick metal, but we'll see how it does on the thin sheet metal.

Next I need to find where I put my extra tips as this one is toast......I just saw them the other day but could not find them tonight.....naturally!

I bought a package at HF, but they don't fit this welder at all.

[94touring]

I just had to buy another 11lb spool, but I use 0.030.  Had to go to the other HF to find it.  I keep a lot of tips on hand so no issues there.

[MiniDave]

I borrowed a Miata axle from Jesse Prather as he races Miatas, so once I finish the motor mounts and I'm sure of the engine position then I can pop the outer one in the hub and measure the short axle's length, then with that info they can get started on mine - I'm guessing it will take them a couple of months so the sooner I can get them moving the better.

I'm going to send them the short Ford axles, there should be enough length that they might be able to just cut them off and machine the one end to match the Miata CV joint, that way they only have to do one end instead of two, or if they want to start from scratch they'll have the Ford end to copy.

I was at Kent Prather's shop last night and we talked about how to change the studs in the front Mini hubs, it's going to be a bit more complicated than just drilling the holes bigger. Turns out the Mini studs have a taper around then to fit a taper in the hub - I've never paid any attention to them before so I didn't know they were made like this..... anyway Kent says the right way to do it is to send it to a machine shop.....have the spacing indicated, then set up on a CNC to make sure the holes are centered and spaced properly. He said the last time he did a set of hubs for an MG he did them on his mill and they vibrated like crazy, so he did this and it fixed the issue. I was just going to drill them and poke them in.....