Now that I have the shell back, I could confirm the exact dimensions of the custom front subframe and start on the framework and engine mounts.
As per the front brace bar I am using 32mm OD structural tube with 3mm wall thickness (See brace bar design Here & Here) and using 6mm plate steel for the engine mounts.
I have a hydraulic pipe bender at home for bending the tube to the right shape and angles and after one failure at bending the tube correctly, the second attempt was better.
The tube was bent in two places with the main spar leading out from the tower. It is dead level and straight out form the tower approx 200mm before leading down on a 45degree angle and then down and inwards a bit to meet the front brace plate.
This tube had to have something to brace it and transfer the load of the engine away from a single weld onto the tower. I had the option of using a simple gusset but I wanted something more substantial, so used another piece of tube. Knowing exactly how to cut tube to join neatly at an angle to another piece of tube can be tricky, but I found a really handy little (free & online) tool for this job. Pipe Joint Template Software is great because once you punch in the details of the tube & angles, it gives you a printout which is cut out from the paper and wrapped around the tube to mark the cut lines.
The result after a cut or two and some filing :
To ensure that the front brace bar and the towers remained in the same position as the shell, I fitted up both pieces to the good shell and tack welded up some quick brace pieces to stop it from moving and twisting while I welded everything together.
The main tubes & lower brace pieces tacked together.
Now for the engine mounts. Unlike most 4E-FTE conversions I've seen that use the factory mounts, I've decided to use something a little different. I am using some rubber mounts from a V8 Land Rover (the same as those used in various Mini engine conversions in the UK). They look small but in actual fact are within 5mm of the diameter and thickness as the factory Starlet mounts. The Starlet mounts are bulkier due the alloy surrounding the rubber part of the mount. Land Rover mounts have a smaller profile. I initiallty thought that these are designed to be mounted on a ~45 degree angle (I confirmed this by calling a local Land Rover repair specialist) but in actual fact 30 degrees above horizontal is better to to ensure that compression forces are greater than shear forces and will deflect further compared to being in vertical only orientation. The result is an increase in the resistance against transmitting vertical vibrations. To be doubly sure, I have discussed using these mounts with my engineer and he has given it the green light and specifically made note to how the angled mounts will hold the engine in place and prevent it from rocking under load.
Once the tube was tacked up, the bracework in the middle of the subframe was cut away and then fitted into the guinea pig Mini front cut (after some heavy handed hammer banging to move panels around to make it match the dimensions of my good shell). The engine was dropped in, positioned to it's approximate final position - to get a good idea of where the mounts would go.
For the gearbox mount, I had to weld on some more 6mm plate (with an additional gusset) to the RHS of the frame to allow for the mount.
This was the first design (at 45 degrees), but it has been cut off and will be replaced with a 30 degree angle bracket instead so that it is under more compression force and not under so much shear force (shear will cause the mount to split in half)
As per the front brace bar I am using 32mm OD structural tube with 3mm wall thickness (See brace bar design Here & Here) and using 6mm plate steel for the engine mounts.
I have a hydraulic pipe bender at home for bending the tube to the right shape and angles and after one failure at bending the tube correctly, the second attempt was better.
The tube was bent in two places with the main spar leading out from the tower. It is dead level and straight out form the tower approx 200mm before leading down on a 45degree angle and then down and inwards a bit to meet the front brace plate.
This tube had to have something to brace it and transfer the load of the engine away from a single weld onto the tower. I had the option of using a simple gusset but I wanted something more substantial, so used another piece of tube. Knowing exactly how to cut tube to join neatly at an angle to another piece of tube can be tricky, but I found a really handy little (free & online) tool for this job. Pipe Joint Template Software is great because once you punch in the details of the tube & angles, it gives you a printout which is cut out from the paper and wrapped around the tube to mark the cut lines.
The result after a cut or two and some filing :
To ensure that the front brace bar and the towers remained in the same position as the shell, I fitted up both pieces to the good shell and tack welded up some quick brace pieces to stop it from moving and twisting while I welded everything together.
The main tubes & lower brace pieces tacked together.
Now for the engine mounts. Unlike most 4E-FTE conversions I've seen that use the factory mounts, I've decided to use something a little different. I am using some rubber mounts from a V8 Land Rover (the same as those used in various Mini engine conversions in the UK). They look small but in actual fact are within 5mm of the diameter and thickness as the factory Starlet mounts. The Starlet mounts are bulkier due the alloy surrounding the rubber part of the mount. Land Rover mounts have a smaller profile. I initiallty thought that these are designed to be mounted on a ~45 degree angle (I confirmed this by calling a local Land Rover repair specialist) but in actual fact 30 degrees above horizontal is better to to ensure that compression forces are greater than shear forces and will deflect further compared to being in vertical only orientation. The result is an increase in the resistance against transmitting vertical vibrations. To be doubly sure, I have discussed using these mounts with my engineer and he has given it the green light and specifically made note to how the angled mounts will hold the engine in place and prevent it from rocking under load.
Once the tube was tacked up, the bracework in the middle of the subframe was cut away and then fitted into the guinea pig Mini front cut (after some heavy handed hammer banging to move panels around to make it match the dimensions of my good shell). The engine was dropped in, positioned to it's approximate final position - to get a good idea of where the mounts would go.
For the gearbox mount, I had to weld on some more 6mm plate (with an additional gusset) to the RHS of the frame to allow for the mount.
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