Backboard and mounting system, and the flush channel construction
AS has been previously mentioned, the design of our ECU prop was intended to make it easy to set up and take down at events.
To that end, lightweight and simple were some of our key criteria.
The backboard (the red board to which the main unit is attached) would be a substantial weight if it was made as a solid ¾” / 19 mm board, as such we didn’t do that!
We needed a hole cut in order to give more depth to the ‘void’ in order to accommodate the trap chamber height we wanted (more on that in another post on the door and chamber!) and the 10 mm rubber seal we had purchased to use for the ‘bellows’.
The board was cut to size, with square corners, out of the same 6 mm marine plywood as the main unit (remainder piece ‘D’ if you’ve followed along from the other posts!).
At this point the lower piece internal corners were also cut with diagonal corners, in place of the radius that would be accurately cut later with a flush trim router.
In order to recreate the required thickness of the board, we added 50 mm (2”) wide strips of 12 mm (1/2”) ply to the edges and placed 100 mm square pieces in the corners for the bolts that would be securing everything to the wall.
![Image]()
We made a simple template to rout the internal corners with a flush trim bit, and affixed it using tape and superglue as a temporary fixation.
![Image]()
The access in the backboard for the electronics space was also rough cut, but this had to be done using measurements from the bottom edge of the board.
We used French cleats to effectively hang our ECU main unit on the backboard. In its simplest form a French cleat is just a piece of timber cut in half at a 45 degree angle.
The simple premise is that the item you hang slides down the angle of the cleat ensures that the item is pulling itself towards the wall making for a secure connection. We used a 1-1/2” x 4”, as we used for the wall frame.
![Image]()
One half is attached to the wall (backboard) and the other on the item to be hung (main unit).
We put the cleats into the voids on the back of the main unit filling the full width, this gave maximum gluing surface and allowed for screws from the top and sides to ensure they remained in place.
Getting them in place on the backboard wasn’t too difficult but it took some thinking about. As stated in the previous post, having access through the gauge and button panel holes was essential.
First step was to position the main unit on the backboard, ensuring it was where we needed it, both square and horizontally central.
Once it was place, we were able to feed in bottom half of cleats that would attach to the backboard through the panel holes.
The location was marked, but we opted to straightaway use wood glue and add some superglue to the bond to act as an ‘instant clamp’. It only had to hold so as not to move when we took the main unit off again.
The backboard cleats were then further affixed with screws from the back.
The panel holes only allowed access to the central and left side cleats, so the third one was added by measuring the thickness of the internal frame away from the central cleat using a scrap piece of the plywood, and aligning the lower edge. Something we found was the case at this point was that not all 6 mm plywood is created equal, and by equal I mean the same thickness! A pair of callipers showed that while one of our boards was 6 mm another was only 5.2 mm, not a big difference in the grand scheme of things, but enough that one had to be careful, it was only by luck that we happened to notice that it looked “a bit of” and checked the gap before we glued it down
Once the top cleat was screwed in place, the lower cleat could be positioned through the electronics access hole on the backboard, a few clamps and some glue and the central cleat was located and able to be screwed into place.
As with the top cleats, the side cleats that located the unit accurately by sitting either side of the internal frames were positioned by measurement.
The cut edges of the cleats were actually quite sharp, so they were rounded off because the point isn’t important to their function. The flat ends were tapered slightly with some light sanding to aid in initial positioning.
![Image]()
We put the main unit onto the backboard, opened the door and marked out the location of the cut out, this was then rough cut out leaving 6 – 10 mm edge in place for accurate routing out later with a trim bit once it could be accurately assembled.
![Image]()
The flush channel was constructed using 6 mm MDF for the ends and 6 mm plywood for the curved front.
The ends were made of a single flat piece for the end and another piece cut with a slightly smaller radius fixed to the inside to create a ledge for the plywood panel to sit when it was glued together. As the front panel was 6 mm thick, the inner piece was cut with a 7 mm smaller radius to create a slight oversize that could be trimmed back later using a trim router to ensure a perfectly matched edge.
![Image]()
6 mm MDF was used, as opposed to plywood, as the curved shapes themselves were cut using the super accuracy of a laser cutter at our local ‘maker space’ (Makerspace Adelaide).
[curves image]
They were glued together with a slotted piece to attach to the bottom of the main unit.
The front panel of the flush channel was able to follow the curve by “kerf cutting’ it on the backside on the table saw; essentially making closely spaced, regular cuts to around three quarters of its depth. A jig was made that allowed for constant spacing between the cuts. We didn’t do any specific calculations (although such calculators exist) we simply made sufficient cuts until it would bend enough, then continued along an entire board. We made the curved board oversize so we could trim it back later.
One end of the kerfed board was cut at an angle to ensure it meets the backboard when in place.
![Image]()
The pieces were put together in place on the unit to ensure that the spacing was correct we added some cross beams for stiffness, it was then glued and clamped.
![Image]()
![Image]()
![Image]()
Once the glue had cured sufficiently, it was time to add the “rivets”. We used ‘Timber cover buttons’ from our big box hardware store (Bunnings) which are little wood plugs, designed to cover over a screw hole.
![Image]()
They looked perfect as rivets and when painted blended in nicely. They were laid out to visualise the spacing, and then hole locations were marked and half inch holes were drilled to recess the buttons into place
![Image]()
The ‘rivets’ were glued into place.
Here’s a shot of what we had at this point.
The French cleat is visible through the gauge holes and markings for the handle are marked
![Image]()
So far I’ve detailed the build of the major parts of the unit itself; next, I’m going to post about either the build of the wall panel, as I know that was a major point of concern for us and likely is for others, or the details for the trap chamber, the details on that and how we got around not using original parts, but fabricated some pretty good (if we do say so ourselves!) lookalikes.
AS has been previously mentioned, the design of our ECU prop was intended to make it easy to set up and take down at events.
To that end, lightweight and simple were some of our key criteria.
The backboard (the red board to which the main unit is attached) would be a substantial weight if it was made as a solid ¾” / 19 mm board, as such we didn’t do that!
We needed a hole cut in order to give more depth to the ‘void’ in order to accommodate the trap chamber height we wanted (more on that in another post on the door and chamber!) and the 10 mm rubber seal we had purchased to use for the ‘bellows’.
The board was cut to size, with square corners, out of the same 6 mm marine plywood as the main unit (remainder piece ‘D’ if you’ve followed along from the other posts!).
At this point the lower piece internal corners were also cut with diagonal corners, in place of the radius that would be accurately cut later with a flush trim router.
In order to recreate the required thickness of the board, we added 50 mm (2”) wide strips of 12 mm (1/2”) ply to the edges and placed 100 mm square pieces in the corners for the bolts that would be securing everything to the wall.
We made a simple template to rout the internal corners with a flush trim bit, and affixed it using tape and superglue as a temporary fixation.
The access in the backboard for the electronics space was also rough cut, but this had to be done using measurements from the bottom edge of the board.
We used French cleats to effectively hang our ECU main unit on the backboard. In its simplest form a French cleat is just a piece of timber cut in half at a 45 degree angle.
The simple premise is that the item you hang slides down the angle of the cleat ensures that the item is pulling itself towards the wall making for a secure connection. We used a 1-1/2” x 4”, as we used for the wall frame.
One half is attached to the wall (backboard) and the other on the item to be hung (main unit).
We put the cleats into the voids on the back of the main unit filling the full width, this gave maximum gluing surface and allowed for screws from the top and sides to ensure they remained in place.
Getting them in place on the backboard wasn’t too difficult but it took some thinking about. As stated in the previous post, having access through the gauge and button panel holes was essential.
First step was to position the main unit on the backboard, ensuring it was where we needed it, both square and horizontally central.
Once it was place, we were able to feed in bottom half of cleats that would attach to the backboard through the panel holes.
The location was marked, but we opted to straightaway use wood glue and add some superglue to the bond to act as an ‘instant clamp’. It only had to hold so as not to move when we took the main unit off again.
The backboard cleats were then further affixed with screws from the back.
The panel holes only allowed access to the central and left side cleats, so the third one was added by measuring the thickness of the internal frame away from the central cleat using a scrap piece of the plywood, and aligning the lower edge. Something we found was the case at this point was that not all 6 mm plywood is created equal, and by equal I mean the same thickness! A pair of callipers showed that while one of our boards was 6 mm another was only 5.2 mm, not a big difference in the grand scheme of things, but enough that one had to be careful, it was only by luck that we happened to notice that it looked “a bit of” and checked the gap before we glued it down
Once the top cleat was screwed in place, the lower cleat could be positioned through the electronics access hole on the backboard, a few clamps and some glue and the central cleat was located and able to be screwed into place.
As with the top cleats, the side cleats that located the unit accurately by sitting either side of the internal frames were positioned by measurement.
The cut edges of the cleats were actually quite sharp, so they were rounded off because the point isn’t important to their function. The flat ends were tapered slightly with some light sanding to aid in initial positioning.
We put the main unit onto the backboard, opened the door and marked out the location of the cut out, this was then rough cut out leaving 6 – 10 mm edge in place for accurate routing out later with a trim bit once it could be accurately assembled.
The flush channel was constructed using 6 mm MDF for the ends and 6 mm plywood for the curved front.
The ends were made of a single flat piece for the end and another piece cut with a slightly smaller radius fixed to the inside to create a ledge for the plywood panel to sit when it was glued together. As the front panel was 6 mm thick, the inner piece was cut with a 7 mm smaller radius to create a slight oversize that could be trimmed back later using a trim router to ensure a perfectly matched edge.
6 mm MDF was used, as opposed to plywood, as the curved shapes themselves were cut using the super accuracy of a laser cutter at our local ‘maker space’ (Makerspace Adelaide).
[curves image]
They were glued together with a slotted piece to attach to the bottom of the main unit.
The front panel of the flush channel was able to follow the curve by “kerf cutting’ it on the backside on the table saw; essentially making closely spaced, regular cuts to around three quarters of its depth. A jig was made that allowed for constant spacing between the cuts. We didn’t do any specific calculations (although such calculators exist) we simply made sufficient cuts until it would bend enough, then continued along an entire board. We made the curved board oversize so we could trim it back later.
One end of the kerfed board was cut at an angle to ensure it meets the backboard when in place.
The pieces were put together in place on the unit to ensure that the spacing was correct we added some cross beams for stiffness, it was then glued and clamped.
Once the glue had cured sufficiently, it was time to add the “rivets”. We used ‘Timber cover buttons’ from our big box hardware store (Bunnings) which are little wood plugs, designed to cover over a screw hole.
They looked perfect as rivets and when painted blended in nicely. They were laid out to visualise the spacing, and then hole locations were marked and half inch holes were drilled to recess the buttons into place
The ‘rivets’ were glued into place.
Here’s a shot of what we had at this point.
The French cleat is visible through the gauge holes and markings for the handle are marked
So far I’ve detailed the build of the major parts of the unit itself; next, I’m going to post about either the build of the wall panel, as I know that was a major point of concern for us and likely is for others, or the details for the trap chamber, the details on that and how we got around not using original parts, but fabricated some pretty good (if we do say so ourselves!) lookalikes.
Statistics: Posted by xXStevenXx — May 21st, 2024, 8:49 pm