SECTION 4 - CREATING THE SUBFRAME
CONTINUED...


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Step 6

Create new subframe spars

Ready, Steady start cutting! The photos opposite refer. In sequence here is what I cut, what I welded, why I cut it and how I replaced it, any questions email me and I will try and explain:

READ THIS:

Before completing the front spar of the subframe you should finish the left and right hand spars ONLY and install the subframe in your Mini. Why? Because unless you are super confident about the tolerances in your subframe then there is a strong likely hood that the holes you make for the bolting points at the front will be out. And lets face it they only have to be out by 3mm (or less) in any direction and there is no way you will get a bolt through there.

You don't want to be widening that hole to make it fit, this is bad engineering and also means that no matter how tight you make the bolts the subframe will shift which means stress on other bolting points and then cracking and then you hit a tree! You can develop the frame overall to a certain stage and then measure the down and cross spars in-situ. This will ensure a perfect fit.

Front of Subframe (Revised 16 Nov 04): Initially I considered creating a front spar as depicted in the image below to connect up the front of the subframe. I have decided to leave this till last as there are several issues that impact on how it is located. Most of these have to do with the projection forwards of the turbo and its subsequent impact on the installation of a radiator and also the front mount intercooler (FMIC).

I realised during the creation of the frame that if I was to follow my own advice that this would impede the installation of the above two items. Whichever system I devise for this will need to be developed after these items are in place. So stay posted. The other issue that also determined where this goes is the exhaust. One idea I have had is that the spar bolts in place rather than as a welded member of the frame similar to a strut brace.

Back of Subframe: Concerning the rear of the subframe (the webbing which goes across the back and also curls back under the body and mounts to the floor near the gearchange), while this is probably perfectly adequate for a 1275 unit, the power output of this new motor requires more extensive bracing.

This is also where one of the engine mounts is located (well actually directly below where the subframe curls back under the drive tunnel) which means you can kill two birds with the one stone. A large main spar joining both towers and then supported by a secondary one can stiffen the frame right up. The upper spar should connect just below the top of both towers about 3 centimetres below the crown of the tower. Locate it almost in the dead centre of the face of the tower.

Too far towards the back of the frame and you risk hitting the firewall. Too far forward and you will either hit the intake plenum support bracket on the engine or the little generator on the back of the engine. You can then possibly install a smaller bar lower own. Having put the engine in I can tell you I was pretty much spot on as far as the location of the back spar is concerned.

Also as you can see in image 11 I have made a small aperture in the back (actually bloody huge, what did I say about measure twice cut once?) of the webbing. This is not explicitly to let the diff housing poke through but just gives that little bit extra breathing room (especially when the engine moves under revs). But don't go too far back as this is exactly where the steering rack passes by at the back and you don't want to be hitting that. Also as you can see in image 8 the engine will need to be tipped forward quite a bit (3 degrees roughly, TBC) which how the water pump pulley is going to stop hitting the tower (In case you were wondering).

Left hand spar: This requires extensive cutting for two reasons to allow movement for the crank pully and the water pump. It is impossible to mount the engine with the alternator in its original position. It is essential that you move it to the front thus avoiding problems with the left hand shock tower. Essentially you have to remove the entire part of this spar to allow the engine to drop through (in other words flush with the cone tower). Then weld spar sections that run alongside the crank pulley side of the engine. If the spar is taken from directly below the crown of the shock tower this should allow the spar to run directly underneath the Starlet engine's left engine mount.

Based on the location of the engine I have managed to create enough room to let the belt of the alternator to pass alongside the subframe spar so it looks like I will be able to mount it at the front after all. Still I'll believe it when I see it.

In images 14 you can see the first right hand spar attached. The supports for this will be slightly different to the ones on the righthand spar due to the crank and water pump pulleys but will follow a similar format. The down pipe will head vertically down from the end and then across almost the complete inverse of the right hand spar. This is mainly due to the location of the oil filter, which will sit directly over the front mount point.

Right Hand Spar: The same applied here as for the left hand spar. While the gearbox doesn't take up all the space occupied by the spar you might as well take the space out from the suspension tower to the front of the frame. There is also a mount here from the front of the gearbox at 90 degrees, which requires the manufacture of a specialised mounting point. More on that in Section 4 – “Putting the Car back together”.

I will also be removing the whole radiator-mounting cowl just to make more room and tidy up the engine bay. I pretty much butchered it putting in the old thermo fan in, anyway. Plus I may put in a remote brake servo so the more room the better.

One other consideration which you may want to take into account is the suspension on this side. The issue here is the possibility of the wheel/tyre rubbing on the subframe. Due to the fact that subframe is not a mirror image on both sides means that there are slight differences on how close the wheel comes to the subframe when it rises during weight transfer/hitting a bump. Have a look at the different ways that the engine bay walls are designed. The one on the right is sharply angled in after the top of the cone tower. Having said that, I had my thermo fan sitting in the wheel well and this never got hit by the wheel, but just something to think about. Also I angled the right hand spar subtly inward to compensate for this fact! (Actually that's crap I just didn't make it square enough but it works in my favour for once!).

I have essentially mimicked the spar design on both sides, the first reason is mostly aesthetic (ie. my need for symmetry, balance etc), but also I can't help feeling from an engineering point of view, balance as far as subframe design must make the subframe stronger and give better weight balance. But while I will be trying to achieve balance in design this may be easier said than done.

You can see in image 5 where I intended to attach the cross spar I just balanced it there to give you an idea. Because of the location of the mount I have revised the design of the subframe because I can't get the down spar where I want it but there is just enough room to run it across and down in front of the mount without the two touching. You can see in image 11 the finished spar with supports and also the cross spar. This is actually longer than the finished product will be, so that I have some room for movement.

There are two issues confronting me at the moment where to put the alternator and what to do about interference with the right hand engine mount. Well guys, with the engine in the frame working the above two points out have become a little easier. I will be mounting the alternator at the front using a special bracket but it will be an unusual design that's for sure. And the right hand engine mount won't be too difficult to accommodate. I am still toying with the idea of creating a custom mounting system for the right hand mount. Stay tuned.

Well guys as you can see from images 9 through 17 I have actually started putting spars on. The one to the left is obviously a support. I didn't have time to finish grinding it so it was a flush fit before I thought I should call it a night. There will be another one coming up from directly below which will mount further along the spar just before where the gearbox engine mount goes to give extra support. Also I have made a few adjustments to my earlier design in image 1 due to the location of the gearbox mount and the amount of space I have around it.

I will put a pic to give you an idea of what I mean. Basically I will have to have the spar move along the front a bit further to the other side of the front mount otherwise the engine may bang against it when it vibrates. But the solution is pretty straightforward. Well in image 18 you can start to see the final product. Once I have her in the car I will take another picture, which should give you a better idea.

    NEW SECTION!!! Well guys I am rapidly running out of space and this section will end up being 200 screens long so I am setting up a separate gallery page for this section. This will show the frame pics till completion. Enjoy.

    NOTE: While you have the engine and subframe out of the car. You may want to think about redoing alot of things that don't get done normally. Such things as replacing the lower control arm bushes etc.

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Step 7

Creating Access for the Driveshafts

Originally I wanted to keep the driveshaft aperture area fairly standard but it has become increasingly obvious that this will be unavoidable. I confirmed my theory with Brad who indicated that he had removed the whole part of this section. And I have proceeded on this basis. It makes things a lot easier and also has the added bonus of giving you a lot more freedom of movement when positioning the engine. Please refer to the next step "Part 4 - Putting it back together", which has more details on what to do with this area.

The only other issue you have to consider is the full movement of the driveshaft in relation to the suspension, which means you have to have the diff centre lined up with the midway point of the arc of the suspension. But the suspension often has greater movement in one direction than the other, that is either more movement up or down. Also you are limited to how low or how high (in relation to the ground) you mount the engine (and thus the diff) by the bonnet (how high) and the intake plenum (which may impact on the master cylinders or the bulk head itself) and general height of the engine above ground (how low). It's getting interesting now hey.

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Step 8

Creation of Lower Control Arm Mounts

This is quite tricky, the original Mini setup has a long bolt that comes from one side of the lower subframe and then bolts to the back of the subframe. The shank of the bolt provides the axle for the lower control arm to rotate around. It is also bent in a shallow U shape as it passes by the driveshaft aperture to allow for movement of the driveshaft (see images 1 & 2 ).

I took off the all the suspension parts off the other subframe the yesterday. But before hand I took some pics of the lower control arm section for reference. The distance between the back of the subframe and the flange on the bolt that compresses the lower control arm is almost exactly 40mm (including bushes). And as I suspected this is almost exactly in line with the edge on the curved aperture edge directly above. So this will be a useful reference point. Another useful approximation tool is to take the control arm bolt and slip the control arm with the bushes inserted onto it and move so it is hard up against the flange, then measure from the edge of one bush to the outer edge of the other. Either way it is close to 40mm.

Now obviously if you obliterate this section of the subframe there is nowhere to mount the bolt. The solution? Create a new left hand mounting area. The solution isn't as radical as you may think and will do the job if done well. Here is my solution which even without having seen or investigated other solutions is probably pretty much par for the course. Basically it requires the welding of a long plate of steel (I chose 1/8" steel). This piece runs down the face of the upper control arm stopper and meets with the floor of the cone tower. This creates a new box section, which will in essence clamp the lower control arm cuff.

The curled edge (see image 6) of the box section directly above the bolt that supports to the lower control arm is almost directly in line with the outer edge of the supporting section of the bolt. So basically when you create the box section the inner face of the new wall will be inline with this curled edge. This makes judging where to put this a little easier. The other consideration you must take into account is the movement of both upper and lower arms. If you have a complete subframe with the suspension still in it you may want to inspect the movement of these arms before welding in bits of metal everywhere.

The big factor here is to ensure that the new bolt you put in is level and correct on all axis (axii?), otherwise the movement of the lower control arm will obviously be out of wack with the upper when they move together. Now the lower arm does have bushes obviously so that there is some free play there (but this is not an excuse to be sloppy with your accuracy), which is also why it has a tie rod! The top arm obviously doesn't need one as it more robustly mounted and is obviously designed to do nothing but move up and down.

Here are the steps to creation of the lower control arm mount. Create initial upright flange and connect to side of aperture:

Step 1 Base Plate - Basically you take a piece of 1/8' steel plate and manufacture it into a shape that mimics the wall of the box section up until close to the top of the stopper for the upper control arm (see Images 7 & 8 ). You can't take it all the way up due to the movement of the upper control arm. Also the wall of the box section is not welded continuously along the side so you need to make a projection (a bit like a dovetail) to fit this gap so that it hits the back section of the aperture wall. Also drill large holes here so that you can make some spot welds for greater adhesion rather than simply weld around the edges.

Step 2 Secondary Bolt Plate: This is the plate that will run down to the bottom and will form the other side of the box section that the lower control arm fits into. So measure a plate that reaches from the floor of this section to near the top of your new base plate and from back of the driveshaft aperture wall to be inline with the back of the subframe where the bolt hole for the lower control arm is. Then seam weld this into place. You may notice that the actual driveshaft aperture itself is made up of two plates of metal. For added rigidity I seam welded these together. One more important point, when affixing the secondary bolt plate in place, clamp it in position and make sure it sits flat (see image 7). Then insert your control arm with bushes in place. It should be a very snug fit. I found that grinding down the curled edge so that it is level with the base plate made for a perfect width once the secondary plate was attached.

Step 3 The bolt: Now I have been giving this some particular thought. There are several different ways you can approach this. Get a bolt of the same diameter as the bolt hole at the back and create a sleeve to go over that bolt to match the diameter of the original (see image 5). Or get a bigger bolt that matches the diameter and just make the bolting holes bigger. The latter approach is the one I will follow. When selecting the bolt go for a high tensile steel type and also base the thickness on the width of the fat part of the original mini item. If you have ever put one in before you will know that there is a bit of resistance when trying to slide this through the bushes so keep this in mind when putting in the new bolt. If there isn't this resistance you have probably selected a bolt that is too thin which will cause suspension problems later on.

Given that here is no need for access to the transmission tunnel I will be running a tubular support from the bottom of one tower to the other that will vastly increase the torsional rigidity. But I will only put this in place after I have successfully located the rear engine mount, as this is smack back between the two cone towers.

Update (Step 3): Have managed to sort this one out to my satisfaction. Originally I purchased a couple of 5/8 of an inch diameter HT bolts from Specialty Fasteners. They based this on a measuring the shank part of the original Mini pin bolt (the thick part). Now a 5/8" bolt is pretty thick and finding a drill that diameter even harder. Plus just by looking at it you knew there was no way it would go through the bushes. So I thought it's close just a little thinner. So I went to another welding place and they supplied me with two 9/16th inch HT bolts. Perfect! Still a tight fit through the bushes but not impossible. So 9/16ths diameter bolts are my recommendation...


Update 15/11/04: Well guys as you can see from photos 2-4 I have completed one mount. I basically followed the procedure outlined above. First I welded a plate to the side of the structure located directly above the control arm. I used 1/8" steel plate for this process, which is almost thick enough to bring it level with the curled lower edge of the structure. I drilled a few holes into it so that as well as being welded around the edges it was also welded in the centre to give added strength and adhesion.

I then designed another plate that essentially lies flat against this in a sandwich fashion; it then rises to be almost flush with the top of the structure where the rubber stopper for the top control arm is located. It then follows the side of the inner edge of the driveshaft aperture and across the bottom of the subframe (See images 10 & 11 ) for a better idea, I will supply better diagrams to give you the idea). I then seam welded everything in place. I will do the other side next week and once the holes are drilled and the lower suspension sorted I can put the Hi Lo's and wheel hubs, brakes etc in and she should be a rolling chassis again!

Oh just remembered that I have to put the tie rod mounts in, brilliant. The next big issue is to sort out the drilling of the bolt hole. This is critical and I am bit nervous about how to ensure that it correct horizontally and vertically as there is not true part of the frame to mark it off against. While the bushes give a fair amount of freeplay I don't really want to have to rely on this. Plus the bushes will obviously wear out quickly if not aligned properly.

Update 21 Nov 04: Well didn't get as far as I would have liked. But have finished both lower mounts. And as you can see in Image 12, one of the lower control arms is in place albeit with a thinner bolt. I have sourced some bolts but they're 5/8ths of an inch and I think a bit too thick but unfortunately 1/2" are too thin so I will see what happens. You can also see that I have sprayed the control arms. They look shmick, don't you think. So now the holes are drilled I just need to source the right bolts. And in go the the bottom arms and then install the top arms and the dry cones and she'll be off the body supports... Oh and the vented disc brakes, hubs and wheels. But she's getting there...

Update 23 November 2004: Well good news managed to find the correct high tensile steel bolts that I have been looking for. I originally went with 5/8" diameter bolts for the control arms but these seemed very heavy for the purpose. Plus I had a feeling that it would be very hard (read impossible) to slip these through the bushes. So I went with 9/16" diameter ones and they are just perfect for the purpose. It is still proving difficult to get them through the bushes but it was the same with the original mini items you just have to struggle through. The things is that once these are through the lower control arms will be done and I can load up the top arms with the new Hi Lo's and then bolt on the rest of the suspension etc. I am feeling more confident than I was on Sunday that's for sure.

Update 25 November 2004: Well almost finished the reinforcing of the frame and have now welded the front mount plate on the right hand side. I also did a bit of weld grinding so the looks a bit cleaner too. Once the subframe is complete to the point of installation I will paint it with primer and then install into the car. The last bit I have to do to say that the whole subframe is truly complete is the tie rods, welding of the crowns of the cone towers and the seam welding of the rear subframe. I also want to reinforce the lower control arm section and of course the bar across the back. Still I have grinded the old weld away so we are ready to go.

Update 1 December 2004: Well things are getting closer to bolting in. Have found the right bolts for the lower control arm mechanism. And actually had one in and tightened up and it worked a charm. Just finalising the seam welding of different parts of the frame. Have also completed strengthening of the lower control arm assembly with the addition of a bottom plate to make the whole section at least 1/8th of a inch all round.

Here's whats left to do on the subframe:

  1. Create caps for open ends of the tube subframe - Have decided to hold of on finalising this as I need to have the tubes open for attaching the lead from the MIG welder.
  2. Seam weld the crown of the cone towers - Done
  3. Seam weld the joins of the rear wings of the subframe - Done (image 16)
  4. Reinforce the bottom of the lower control arm section - Done (image 13 - 15)
  5. Welding of a small reinforcing plate on the front of the right cone tower.
  6. Reinsert spar between cone towers. Can only be done with subframe in car otherwise I will repeat my last effort (the frame ended up not fitting) - Done (as stated bolted the whole frame in and then spot welded the cross spar fits perfectly this time!)
  7. Grind/smooth all welds - Done, plus with the use of the primer filler all the yucky nooks and crannies get filled so look quite good now.
  8. Wire wheel entire frame - Done (will require full rubdown again with grease&wax remover before ready for painting
  9. Sand inside of cone towers - Done
  10. Prime all parts of the subframe no longer in use for welding purposes - Done

Then comes the suspension...

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Step 9

Create the tie rod mounts.

Update: I have decided to hold off on installing the tie rod mounts till after the engine is in because I remember having some trouble getting the engine in with the mounts installed. But this was due to the excess metal I left on the mounts when I cut them out of the frame. But either way I know they will fit because I tested it earlier.

Well this is going to be tricky. I've got to stop saying that. Everything's tricky in this bloody endeavour. Anyway. I still have the mounts which I cut out of the old subframe (image 1). These are complete with the original mounting hole attached. So essentially I will bolt these to the front mounting plates and then trace around the plates. Cut the excess out and weld to the mounting plates. May also incorporate some additional strengthening as this has obviously been lost with the removal of the front crossmember.

Here are the images of the two tie rod mounts sitting on the ground. As you can see when I cut them out I retained the hole in the front crossmember where it bolted at the front. This allows me to ensure that they are bolted up to the same point making locating them correctly that much easier. I am simply going to weld them to the mounting plates and then reinforce the mounts.

I will supply additional pictures as I progress…

Update 12 March 2004: Well making great progress now. Have welded both tie rod mounts to the frame. At the moment they are simply seam welded across the front and I have made a base plate for the right hand mount (images 2,3 & 5). The left hand mount requires a bit more work but it is at least in place as well. I simply used the bolt hole as the locator and then made sure that the tie rod would meet up which it does in both cases. The bolt hole being the same hole where the front of the normal mini subframe bolts to. Will have to devise some way to reinforce them a bit as obviously the original design has more support. But I don't think this will be a huge problem.

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Step 10

Finalise Suspension.

Sometimes when you do things you realise that other things have to come first. By installing your fully functional suspension before you lower in the engine you ensure that all the cars geometry is in similar nick to how it will appear when the engine is in. This will help you to place the engine in the correct spot.

So the tasks to be completed here are:

• Refurbish suspension parts (eg. lower and upper control arms, wheel hubs etc) if necessary - Done except for actual cones. Wil try and take the ones out of the rear subframe if I have time.

•  Install lower control arm with new bushes - Done the bolts worked a charm (see image 2).

• Install upper control arm (I have bought a set of Hi Lo's so I will be installing these in conjunction with this) - The arms have been done so just a matter of installing them. Have to rub down the interior of the cones towers with grease&wax remover before giving them a coat of primter then we're away. - All Done as you can see in images 7 through 11.

•  Insert Wheel Hub (possibly replace current ball joints if necessary. mine are pretty much brand new so not much point for me :-)). Oh and new Timken bearings... Done

•  Attach Disc Brake Assembly - Done

•  Attach CV Joint - Done

•  Attach shock mounts and shock absorbers - Have to find bolts to mount them first. - Have the shocks and the mounts but no bolts to attach them to the side of the engine bay. This will probably occur this coming weekend if I have time on Sunday (9 January 05)

This is theoretically as far you can go in this area until the driveshafts arrive and this is still a while a way in the process of things. But with the cones in place you should be able to lower the car to the ground for the first time in a while and push it around. Now here comes a dilemma without an engine the car will sit quite high at the front. And if like me, you haven't got a around to doing the rear dry cone subframe the car will sit even higher.

But this may work in my favour as I want the engine to angle slightly forward in the engine bay and if the car is high at the front angling down to the back that will make the process a bit easier (wow just thought of that then whoo hoo). Next stop, possibly the most important part of the project the engine mounts. This is serious, stuff this up and you may have to go back to step 1 with the subframe. Or spend hours grinding your mounts off!

Revision Note 7 January 2005 - Well as with all things I have changed my mind on the setup of the car prior to installation of the engine. I decided to leave the cones out of the car for the time being so that she currently sits on the bump stops. This is because this will replicated the suspension being at full compression. This will then allow me to know exactly how deep to place the engine as far as the differential is concerned. Too high in the engine bay and you run the risk of having the driveshafts hitting the subframe under full suspension compression (which could bend your driveshaft). This is more a concern because of the offcentre diff.

I have taken JAM's advice on the type of paints to use on the suspension parts. Here are his tips:

Subframes:

Kill Rust Etch Primer - thinned with turps and sprayed with compressor - 1 coat
Kill Rust Black Epoxy Enamel - thinned with turps and sprayed with compressor - 2 coats

Suspension:

Soaked in Kero
Wire brushed thoroughly
White Knight Hammertone 375g pressure pack (Charcoal colour) - 2 coats

Very tuff paint! I am actually surprised. It should resist stone chips!


You will notice in image 10 that the car sits very low this is because it is sitting on the bump stops. This is a purposeful thing as the this simulates the suspension at full compression. So when I go to install the engine I know how far to drop the engine to allow for the rise of the driveshafts so that they don't hit the subframe.

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Step 11

Finished Subframe.

This is my version of the subframe. There are obviously different ways of doing it and maybe I have gone a bit overboard with the changes and the strengthening. I chose to remove the alternator and place it on the otherside of the engine. Essentially as I do not intend to run the air con I placed this unit in the position previously taken up by the gas compressor so have to make holes in the side of the engine bay or strange brackets all sorted... as I said before I have been told it is possible to do it with the alternator still in its original position but I don't know how. Anyway in the next step I will show you what I did to the engine and then how I created and attached the engine mounts.

Most of the front mounting of the subframe I did in situ. Firstly I created the left and right hand spars having placed the subframe in the jig. I then place the engine in the subframe jig to get an idea of how the mounts sat. Having completed this part I cut the engine bay by rough approximation and then placed the subframe in the engine bay then finalised the cutting of the engine bay. Having done this I then created the mounting plates at the front and created front down and cross spars to meet up with these plates. It was then a case of just strengthening the angles with gussets. I then bolted the remnants of the tie rod mounts to the mounting plates and voila (chuckle chuckle) one subframe. Overall I think it took me at least 50 - 100 hours to fabricate the parts and weld the subframe, and much more if you include all the side issues such as creating the jig etc etc.

Update 5 December 04: Truly, finally finished...That is she is ready to go into the car to start looking at the engine mounts. I should have the full suspension and wheels on the car by next weekend and then I go on holiday.

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FINAL NOTE: While I have endevoured to give you as much information as I can, I am not a professional engineer, not even close. So anything you take from this website is at your own risk. Due to the increasingly litigous society in which we dwell I will also be unable to develop or send out full specs for the subframe. For the same reason, I won't be making subframes for people. The fact is as much as people like to say that they won't seek you out when things go wrong, they will, and usually with a lawyer in tow. Also even if you make a subframe similar to mine you will still need to get an engineering certificate.

ON TO SECTION 5 - ENGINE INSTALLATION AND MARKING OFF

BACK TO SECTION 3 PART 1 - CREATING THE SUBFRAME

BACK TO SECTION 2 - REMOVING THE ENGINE FROM THE HALFCUT

BACK TO START - STARLET GT CONVERSION