SECTION 6 - CREATING THE ENGINE MOUNTS

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Plan for subframe2
Plan for subframe

Step 1 - Creation of Engine mounts

An Overview

(All descriptions are based on you viewing the engine bay from the front of the car)

Location of Mounts

The engine connects to the subframe in 3 places:

  1. At the front of the engine on the far right hand side front corner on the gearbox.
  2. On the left hand side at a 90-degree angle to the head of the engine.
  3. At the back towards the left just behind the bellhousing.

Essentially all the engine mounting brackets are essentially two arms with a bolt through the centre, which clamps a rubber disc inside the engine mount. An assembly of two vertical arms or a box section will do the job. The actual attachments obviously come with the engine so as long as you make them fairly precise as far as width is concerned and of course in the right place and vertical, then it should be fairly straight forward (he says laughing to himself).

I proceeded with the left and right mounts first. Mainly because these are the easiest to get at but also because it is these two that really determine the location of the engine both vertically, longitudinally and horizontally. You are probably best off working with the left hand mount first because the engine mount on this side will drop easily into the cup on this side whereas the right hand mount is a little more inaccessable because of its location in the front right of the engine bay.

Now whichever way you go you will need to make sure that the initial location of the first mount is correct. What I mean is that if you place the first engine mount in a wrong position then you will end up with all your mounts out, or you will have to remove them and start again. So obviously this is important. But if it makes you feel better, I was close but no cigar as far as my first mount on the left hand side, which necessitated me removing the whole mount and starting again. But even you are out, just by virtue of putting a mount in will allow you to get a really good idea of where is really should go. A bit like a marking off point. Before you have this point it is to a certain extent guesswork. This is mainly because it is fairly restricted there and so marking things off is quite difficult and a little inaccurate.

The rear mount near the diff while being the hardest to get at (unless you have a pit) is in some ways the most straight forward as you already have the cup that it mounts to created for you. Al you have to do is organise how you are going to lower it to get past the back of the subframe. This mount is obviously under a lot less stress than the other two and really performs an anchoring role to stop the engine moving backwards and forwards under revs, but they didn't put in three mounts for no reason.


Mount Design

The engine mounts are approximately 60mm in width which means obviously that the internal width of your mounts has to be 60mm or a couple of millimetres larger to be safe. My engine mounts will be made of 1/8" steel similar to the steel I have used to make the reinforcing plates for the subframe and lower control arms. Now here is something else that is interesting, the bolts to go through the mounts are obviously metric, but two are 10mm bolts and one is a 12mm bolt (left hand mount). I am sure there is a reason though I have no idea what it is...

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Installation No 6 with fugue
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Installation No 6 with fugue
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The mount almost finished but far from perfect but its far from complete
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Installation No 6 with fugue
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Installation No 6 with fugue
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Installation No 6 with fugue

Step 2 - Left Hand Mount

There will be reinforcing gusseting along the spar and also under the mount as well (see Image 1). The basic format is a vertical rectangle with the top cut off (images 3 & 4), as described earlier. Now this will be sitting on the left hand spar tube at 90 degrees vertical to the tube, which obviously makes it a little unstable so a fair amount of support will have to be incorporated at the bottom to support it. Now technically these supports should rise up at a right angle from the spar, but if you are going to tip the engine forward then obviously there is going to be a small amount of angling forward, but not a great deal. I also cut a though section in the floor of cup to take the spar which makes it a little more secure.

As you can see in Images 3 & 4 I have completed the basic welding in of the left hand mount. It can be quite tricky to make sure the engine is in the right alignment then mark and the create the mount and then weld it in. Mine was out by about 2-3mm. Basically it is a case of creeping along the spar by welding plates next to each other like Dominoes until you reach the correct location. This isn't good engineering but sometimes you have to go with what works (the drawing refers).

Update 6 March 2005: As you can see things have progressed a little. As well as finalising the welds of the cup itself I have also re-done the welds on the support from the cone tower and also created a new triangular support that goes from the cone tower to the top of the engine mount cup. This is perhaps a little overengineered but better that, than under engineered. The triangle was mainly to add torsional strength in the downward direction once the load of the engine's weight is placed on it. I will be putting a similar ridge across the right hand spar (though not as impressive). Apart from tidying up the welds etc this mount is done.

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Installation No 6 with fugue
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Welding the bits together
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Bolting her together to see how she fits
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Installation No 1 with fugue
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Installation No 5 with fugue
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Installation No 6 with fugue
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Installation No 6 with fugue

Step 3 - Right Hand Mount

This is both on one hand easier than the left hand mount but also harder (images 1- 6). This is because it hangs down, rather than supports from underneath. So ensuring it meets up can be easier, this area requires a fair amount more reinforcement especially because it is located at the corner of an angle (a weaker area than a straight spar obviously!). Also being 60mm wide makes it wider than the spar it attaches to (38mm) so one side is ultimately less unsupported in comparison to the other (see image 11 ).

Note: You will notice that I call the mounts Engine side mount and subframe side mount. This is because technically you could probably get away with calling them both mounts either way it starts to get confusing. So the Engine Side Mount (ESM) is the mount that is bolted to the engine block including the rubber disc itself, and the Subframe Side Mount (SSM) is the cup appendage welded to the frame to take the rubber disc thingy. OK.

  1. Construct SSM - as per images 1 and 2.
  2. Attach ESM to engine and then place engine in subframe. This assumes that you have constructed the left hand mount at least and that the engine in bolted loosely to it. Raise the right hand side of the engine so that the engine is level in the engine bay (instructions here).
  3. Create Attaching Plates - Once sure that the engine is level make measurements (ensure that the cup top surface is level with the spar) and construct two plates that go on either side of the spar and then reach down to the flat top of SSM cup. Then tack weld in place.
  4. Create cross braces (Optional) - As per image 7 I created tubular cross braces to stabilise the mount for sideways movement and to strengthen the subframe generally. You don't have to do this and may get around this with a different style of frame in this area.

Having said all this the one thing that makes it easier is that it runs (almost) parallel to the right hand spar and is also one of the ways to ensure the engine is perfectly east west in comparison to the car. Also you can make a custom mount away from the frame and then mount it to the actual engine mount and then bolt the whole thing in place. Much easier. I bolted the frame mount securely to the actual engine mount (to become essentially one unit) and then welded some plate and bar steel from the spar down to the mount to keep it in place while I remove the frame and finalise the welding of the mount with the frame out of the car. Image 1 gives a rough design of the mount.

Update 6 March 2005: Well I have installed and cut this mount twice while in the car to get the engine to sit perfectly horizontal. But with the subframe out of the car the mount looks a little strange. I am therefore trying to find a way to keep the mount located in the right position while I cut the spot welds and do a proper job on it similar to the job I have done on the left hand mount. I'll keep you posted.

Update 9 March 2005: I managed to find a solution to the problem. Having bolted the engine into the subframe this holds the whole frame steady in comparison to the engine. I just cut the mount out again for the 3rd time, cleaned off the spots welds and widened the bolt holes to the 12mm diameter that they have to be. I then bolted the mount to the engine so that it would remain stable and then started creating the plates of steel to attach it to the right hand spar. The mount now sits at 90 degrees to the east west direction of the engine/gearbox as it should so I think I have finally nailed this mount which was taking up much time and energy. I will supply a little schematic of the mount to help visualise what I was doing.

To give the spar additional torsional rigidity as stated in the previous step I will be adding a ridge to this side as well. While this is not entirely necessary I just feel that given the location of the mount on this side that the unsupported section of the spar will be under added stress. Plus as previously stated the engineer is talking about having me bolt the subframe to the engine wall in some way. I may have got him to revise his ideas but will have to confirm. Either way this will incorporated into the frame.

Update 12 March 2005: I have made additions to the area surrounding this mount (image 7). This pretty much is it for this mount. Probably a little bit of overkill but like I say better to overengineered than under. Also in case you passed it because it is in a different section I have also done the tie rod mounts select this link to go back to that section.

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Bolting her together to see how she fits
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Welding the bits together
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Installation No 1 with fugue
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Installation No 5 with fugue
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Installation No 6 with fugue
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Installation No 6 with fugue
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Welding the bits together
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Bolting her together to see how she fits
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Bolting her together to see how she fits

Step 4 - Rear Mount

This is probably the most difficult mount to create because of its location. The mounting cup itself bolts to the rear of the engine on the left hand side of the diff (from the front) via two bolt holes. Otherwise it is identical to the other mounts in the way it is designed. Now the biggest trick here is locating the rubber mount itself. Because of the faux transmission tunnel there is nothing but empty space on which to attach the mount.

The solution? Here are the points to cover in sequence:

  1. Remove rear mount from donor vehicle
  2. Take one piece of rectangular pipe (RHS) which is considerably longer than the distance between to the back flanges of the Mini subframe (image 1). Cut the rubber disc section of the rear mount from the rest of the mount.
  3. Weld this to the RHS so that it is a perfect 90 degree angle to the tubing (image 2)
  4. Take Engine Mount (the cup that bolts to the rear of the diff) and augment. This involves welding a plate to the back of the mount which take the existing top hole and moving it down to the bottom bolt hole. By attaching a plate to the back of the mount and welding it there (see images 4 & 5) you can then use the top bolting hole aswell.
  5. Assuming the engine is in the car and level, bolt the RHS with the rubber engine mount attached to the mount on the diff and tighten to the point where it will remain in place by itself. You should find yourself with the situation of having the two mounts joined together, and the bar stretching across from one arm of the rear subframe to the other (see image 3, excuse the angle it was pretty tight in there).
  6. Using a permanent pen mark off the spar where it makes contact with the sloping portion of the rear arms of the subframe. This will form the point at which the ends of the spar will start sloping inwards (see image X).
  7. Once you have marked these point fashion the ends of the bar as per image X and then return to the mounting position.
  8. Once satisfied that the bar is both parallel with the back of the subframe and engine, secure in place and make the necessary spot welds to secure it in place.
  9. Once you have removed the frame to finalise all the welding on the subframe you can augment the rear crossbrace with metal plating similar to that seen in image 6, 7 & 8.

PLEASE NOTE: Do the brace spot welding in situ, as doing it with the frame outside the car can leave your frame or the cross brace well out of alignment.

 

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Welding the bits together
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Bolting her together to see how she fits
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Installation No 1 with fugue
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Installation No 1 with fugue
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Installation No 1 with fugue
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Installation No 1 with fugue

Step 5 - Finished Product

Hopefully if everything has gone according to plan you should have a subframe that bolts to all three engine mounts and keeps the engine both secure and level. If you have done this then congratulations. As for me it has taken so long to get even close to this point it is amazing but at the end I have derived a good deal of satisfaction from this. And I think produce a pretty well designed subframe for a home engineer!

Also don't forget the little things that need to be put on before the frame is put back on the car, like the mounts for the brake hoses (the little tab things with the holes through them in image 4) I almost finished without putting these on. When doing this make sure you have the engine in the frame to make sure that you don't make them too long and they clash on the engine. The other one is the upper control arm bump stops (image 5). I simply wire wheel the original plates, then went to Clarks rubber and got of piece of flat 1/4" rubber and bonded the two with contact adhesive. Will give them a coat of chassis black and Bob's your illigitimate son.

As for the aperture for the gearchange that is dealt with more in the next section. Also dealt with in the next section is the repairs I am making to the engine bay as it requires a tidy up so you will be able to see how that goes.

Update 27 March 2004: Well finished the frame and apeture for the gearchange etc. I have begun painting it with my new spary gun. So hopefully the painting of the spray gun will be completed by the end of the weekend and then I can get started on the engine bay. Here are some pics of the subframe painting.

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 am 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.

ON TO STEP 7 - ATTACHING THE ENGINE ANCILLARIES

BACK TO STEP 5 - CREATING THE SUBFRAME

BACK TO START - STARLET GT CONVERSION


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