Connecting Rod

[David CambridgeParticipant @davidcambridge45658]

Hello All

I’m part way into making my Wyvern engine and the next job is the connecting rod, but I’m a bit stuck on how exactly to do this.

I’ve thought through the steps involved, and my plan is to machine the parts of the drawing shown in grey from solid, and then to braze on the foot shown in red.

I’m happy I’ve got a process that will work apart from the fact I can’t figure out how to achieve the part shown in red. More specifically, I can’t figure out how to make sure it is aligned with the hole in the little end bearing. I’d be really grateful if anyone has any tips.

David

[David CambridgeParticipant @davidcambridge45658]

Connecting Rod

[JasonBModerator @jasonb]

Far easier to just start with some rectangular bar. A female centre can be used to support the ball shaped end

Failing that if you want to fabricate then leave the rod parallel, solder on an over thick end plate then you can put it back in the lathe and turn the end which will make it square to the rod

[David CambridgeParticipant @davidcambridge45658]

Thanks Jason – both seem sensible, but I’m still stuck on how to drill the holes in the foot. i.e. they have to be at right angles to the little end hole, and I’m having a real mental block on how to set that up ?

Edited By David Cambridge on 30/07/2017 13:17:09

[JasonBModerator @jasonb]

Assuming you have a mill then hold the bar vertically, mill the end flat, use edge finder to locate ctr of bar and centre drill, use handwheel dials or DRO to position the other two holes. Ends could be faced back in the 4-jaw if you prefer

If just doing it on teh lateh then basically teh same method but hold the bar horizontally with end facing teh headstock

Once you have done the holes pop it in the 4-jaw with say 1" sticking out, turn round and then form the ball with a ball turner. Back to the mill and holding in the vice mill a flat on one side of the ball then drill and ream, flip it over and mill flat on the other side to bring small end to width.

Back in the lathe either between ctrs of holding the very end of the foot in the 4 jaw and female ctr (hole made will do) supporting the end rough out the rod parallel then turn the taper

Edited By JasonB on 30/07/2017 13:36:43

[David CambridgeParticipant @davidcambridge45658]

Thanks Jason – yes I see. That works well for starting off with the flat bar, and hence presumably why you say it’s easier than fabricating it.

David

[John ReeseParticipant @johnreese12848]

If you have the components made, it is a fairly simple process to make a fixture to maintain alignment while silver brazing the rectangular flange in place. Start with a piece of rectangular bar. Drill and ream a hole that matches the hole in the top of the rod. Place a pin in the hole. Set the connecting rod on the pin. If necessary make a spacer to go under either the rectangular part or the top end of the rod. The idea is to have the center line of the rod parallel with the top of the fixture bar when the long side of the rectangle is touching the fixture. I assume there is a small spigot on the lower end of the rod to align with a hole in the rectangle. If not, drill the end of the rod and the rectangle so you can use a small pin for aligning the parts. When the parts are in alignment go ahead and silver braze. You will probably need to put a lime wash or anti-flux of some kind on the fixture bar so you do not wind up silvering the rectangle to the fixture.

[Martin ConnellyParticipant @martinconnelly55370]

If you have a mill and have not started the component yet you could machine the little end hole, three sides of the end plate and the end face with one set-up. The three sides that are machined in the end plate will make it easy to set up to machine the fourth face and drill the two other holes. You may be able to do it with milling on lathe if that is all you have.

Martin C

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