More holes than a mole infested golf course

This post is more about assembly technique rather than the pedals themselves (just sayin' like).

Punch it

I start with two side pieces each with a single 10mm diameter hole near the corner (the “pedal axle” hole I am calling it), drilled according to the plans. The front support, main/spring support and rear support pieces need to be fitted to the side pieces. To do this I need to drill holes for the M4 bolts in all these pieces. It is highly desireable that these holes should be drilled in such a way as the two side pieces match in alignment ab-so-lu-te-ly per-fect-ly.

To do this through measuring the position of each individual hole on each piece would be quite time consuming. Instead I developed an alternative method, which is still quite time consuming. For this I use the plan drawings that I have already made on the comp-pute-ter. I will try to post these, or post a link, later on but they need a bit of tidying up to remove artifacts from earlier unused variations on the design.

The first stage is to print out the plan. These are printed to the correct scale – which should be obvious because the plan should fit the actual piece in size. I cut out the plans outline of the side piece and carefully tape it in position on top of one of the side piece (I'm doing all this of course twice for the two pedals – but will only describe it as though I'm making one). Where I have marked the bolts to fit on the plan, I centre punch holes. Of course the centre punch passes through the paper and makes an indent in the metal – marking out where to drill. After all holes have been centre punched I remove the plan from the metal and grab hold of the other side piece.

I take the two side pieces and I carefully line them up one on top of the other - the most important bit is to line up is the 10mm pedal axle holes. I messed up drilling one of these holes originally so had a second go drilling in the corner below. 

The hard part here is getting the two pieces clamped together without disturbing their position with the tightening of the first clamp (tends to rotate the top piece as the clamp starts to grip but hasn't quite got them 'clamped down' yet). To help I use one of the shaft bearings through the 10 mm hole - these bearings are slightly longer than the 1/4" thickness of the side piece, and so a few mm sticks through into the second piece making pretty sure these two holes line up. Also of use is some repair tape which seems to hold the pieces together well as I tighten up the 'big G' clamps. 

With the holes on one side all ready centre punched, once the pieces are clamped together and the whole thing clamped to the workbench I am ready to drill. The important thing here is to drill vertically down at a right angle to the piece. 

The next part is a little bit trickier. I need to drill the centre pieces (front support, spring support, and pulley/rear support) through making sure that a) the multiple holes in each piece match exactly with the holes already in the side pieces and b) the pieces are in the correct position. After a little head scratching, this is the technique I used to do it; the results came out pretty well, but only I think because I took the time and tried to be meticulous with it.

I take the printed plans I used to position the centre punch for the holes, checking that the lines on the paper are an exact match in size for the pieces on the workbench. I retape the plan to the one side of the side piece. Only one side piece can be used with the paper plan as it is - if I wanted to do the opposite side piece the same way, I'd need to print out a 'horizontally flipped' version of the plan. As it turns out I don't need to do this. 

Anyway, once the plan is as perfectly placed and taped onto the metal as I can get (the holes I just drilled help here), it is time to mark out where the pieces fit. To do this I take my modelling knife and ruler and cut the lines on the plan marking each piece. The knife passes through the paper and cuts into the aluminium. I don't cut completely the way along each line because I don't want to slice up the paper too much and risk it coming loose from the metal. 

Cut it

 

After removing the plan, I can see where the centre pieces should go by the cuts in the aluminium. The plan now is to clamp the centre piece in position and then pass through the recently drilled holes in the side piece, into and through the centre piece. The holes in the side piece should mean that everything lines up 'ab-so-lu-te-ly per-fect-ly' . Again this is made slightly tricky for the rear supports and spring supports due to the clamp tending to twist slightly before it fully grips. But it is do-able. Smaller clamps help here. The bigger the clamp the less room it tends to leave for the drill to get in. I couldn't manage to get every hole first time due to this, but by drilling one or two holes then fastening with a nut and bolt, I could reposition the clamps to get access to other holes. 

I say slightly tricky for the rear supports and spring supports, for the front support/pedal stop I found it nigh-on impossible. Small clamps can't get in because the piece is set away from the edges, and my 'big G' 4" clamps are right on the limit of reach, and then they block the drill space. In the end I gave up and did a hybrid method, clamping the piece, then marking through the side holes with a pencil, then drilling. The first attempt at this didn't go quite so well, and I recall having to file out a slightly 'oval' shaped hole in order to get the piece to fit exactly to the knife-drawn outline. Second attempt was better, so m'eh. 

Once all the holes are drilled, I use my 20mm M4 bolts and washers and nuts to fasten all the pieces to the side piece. I am well chuffed at how sturdy the whole thing feels. 

Rear support, main support and front support pieces all bolted up to one side piece

Only one side of the story

Next up is fitting the opposite side piece. I keep everything bolted together for this. My plan is to clamp the side piece to the unit and then drill through into the centre pieces using the holes in the side piece as the guide, again making sure all the holes line up 'ab-so-lu-te-ly per-fect-ly' . The most important thing here, and it is critical - if i get this badly wrong I will mess up the whole pedal unit, is to get the alignment between the two pedal axle holes on each side 'ab-so-lu-te-ly per-fect'. If I don't the pedal could jam or swing off to one side when it's pressed. 

To do this i lightly clamp the pieces together, fit the bearings to the 10mm holes and place a length of 8mm shaft through the hole. With the pedal box lying side down on the workbench, I place my protractor on the inside of the side piece and try to eye up the 8mm shaft to check its exactly at 90 degreees. I do this at both the front and underneath sides of the pedal box. If the shaft ain't quite right I find I can gently use it as a lever to pull the loose side piece into position. I check everything with my square before subjecting the metal to the drill bit. 

Once a few holes are drilled, I drop in a few bolts as extra protection against pieces coming out of alignment. Tighten a few nuts, reposition some clamps and drill the holes I couldn't get to the first time. 

In other news...

I have changed the position of the front support piece (which also acts as the pedal stop) to make the pedals in floor mount configuration. I decided to do this because if I make the pedals in 'overhang' configuration I won't be able to test them until I have built a suitable wheel stand. Based on my current build rate this could be months down the line. Instead I will build them in floor mount configuration and knock together a quick(er) wheel stand - although I don't have a final design, or even concept sketch for this yet.