|
|
Next story>>> Back to news index>>> Go home ! >>> 6th June 2010 Meccano-built Trunnion bender
A couple of weeks ago the latest edition of the International Meccanoman Journal landed on the doormat. Amongst its pages was a suggestion from Philip Webb Build it…
After a couple of aborted attempts at making a Meccano bending break type machine I decided that there was a much simpler solution. The trunnions need to be bent so there is a clear ½ inch between internal faces. This means bending it around a former. The trunnion also needs to be held in place while the bending is carried out. To make this simple jig, select 14 of P/N 2, 5½ inch standard strips (11 hole), and bolt them together through holes 1,2, 10 & 11. Use a couple of drifts or rods to ensure they are all aligned. Then bolt two fishplates, through their slotted holes, through holes 3 & 9 of the strips using pivot bolts. This will help maintain good alignment. A stack of 4 P/N 5, 2½ inch standard strips (5 hole), are bolted through one of the fishplates and secured with a couple of washers and a locking nut. This should be tight but allow the stack of stripes to be swung clear for insertion and removal of the trunnion. A long bolt and a threaded coupling are used to lock the jig up and clamp the trunnion in place. Finally two 2 inch long rods have collars fitted and are used as alignment pins.
How it works…
Clamp a trunnion in place using the alignment rods passed through the top and bottom holes of the trunnion and through holes 5 & 8 of the jig. Clamp it up tight. As the fishplates are slightly thinner than the trunnions, there is plenty of clamping force applied. Bend the trunnion over the former with your thumbs to get it started and then use a hammer to get it the rest of the way.
Turn the jig over and repeat the exercise to fold up the other side. Finally place the jig on a flat solid surface and gently tap the corners square.
I was suprised how accurately this little jig produces nice neat little parts. You will need to repaint after the bending so you might as well strip them first and bend them up in their stripped state. You can then decide how to finish them, if at all. If you leave them as bare metal some form of rust inhibitor will be required. I have just given these ones a spray of WD40 and polished them dry with a rag for now but I think I will be repainting them eventually - or even zinc plate them... Ralph. And another... At the time of writing I had not realised that Philip Webb had already made a similar jig and mentioned it on the Spanner II list. Here is his explanation of how he made it and how to fold the trunnions:
|
regarding bending trunnions to create a very useful looking part. This started a discussion on the Spanner II list debating how to achieve these bends. For those, like me, who do not have access to workshop facilities I have made a simple Meccano-built jig that will allow anyone with a hammer and a hard flat surface to make neat folded trunnions. 
The Trunnion is secured by bolting through into the two Threaded Cranks mounted beow the