Stuart 10V conn rod

[Neil AParticipant @neila]

I have just started machining the parts for a Stuart 10V engine. The set is quite old and it still has the forged crankshaft and hot pressed brass for the connecting rod and the eccentric rod. While the iron castings and the crankshaft are fine, the hot pressed brass parts are somewhat bent or distorted.

Has anyone got any advice on straightening the brass parts? Not knowing the exactly composition of the brass, I am not sure how much I can bend them without causing cracking.

I would like to use the supplied parts, but if they do crack, it just means buying new parts or making from scratch. Any advice is welcome.

Neil

[JasonBModerator @jasonb]

These parts are usually quite a ductile brass otherwise they could not be stamped. It would not hurt to anneal it first – heat to 350-400deg C (very dull red) and then just leave to cool in the air.

[Neil AParticipant @neila]

Thanks Jason, that will give me more confidence to attempt to straighten the parts. The conn rod is the worst, the small end is very obviously not at right angles to the rest of the rod, the bend is quite close to that end.

Perhaps it caught in the dies when it was still very hot. I will take your advice and anneal it first, give it the best chance of success.

Neil

[Mick B1Participant @mickb1]

When I built my 10V, I only had a Unimat 3 which was too small to swing the eccentric rod to bore the strap, so I cut off the rod, bored the strap and tapped it so that I could turn a new rod separately from bronze and screw it into the strap. It’d be a bit more complicated to do that on the conrod because of the fork end, but if you’ve any milling capability it should be possible?

[Neil AParticipant @neila]

This is just a quick follow up on the conn rod. I did do the annealing before bending, I don’t know if the material age hardens, but why take the risk. The features are now all within 0.2mm and there is sufficient machining allowance for everything to clean up. So I have decided not to try and bend it any further.

I notice that Stuart’s now supply what looks like a CNC machined blank for the conn rod. Perhaps the dies had worn and it is a cheaper option than re-sinking the dies. Obviously fewer rejects with this method.

Out of curiosity, I’m not sure if the shank of the conn rod is tapered or not. Measuring both ends of the shank I have less than 0.4mm difference in diameter on the stamping. It needs cleaning up, do I machine it parallel or shall I go for a taper? I would be interested to hear what other builders have done.

Thanks everyone for your input.

Neil

[JasonBModerator @jasonb]

Stuarts don’t do any brass stampings now parts are either partially CNC machined or cast.

It should have a bit of taper, say 1/32″ or 0.7mm difference in dia top to bottom.

[John PurdyParticipant @johnpurdy78347]

Neil

I just checked my #10 ( mid 70s vintage) and the bottom of the rod measures .229 and the top .200, so close to Jason’ suggestion.

John

[Neil AParticipant @neila]

Thanks everyone for your input. I thought the drawings showed a slight taper, but with the slight miss-match on my stamping and the way the flash had been sheared off I was not sure.

A tapered rod it will be. All I have to do now is make sure I don’t make any mistakes!

Neil

[Andrew CrowParticipant @andrewcrow91475]

Hello Niel, someone gave me a very old V10 kit that had been started by his father, some of the parts have been machined including the con-rod, unfortunately like yours it’s been distorted and machined incorrectly. I intend to either solder in a piece of brass at the small end to see if it is salvageable, failing that I will make one from a bit of phosphor bronze. So even if you do make a mistake or the part can’t be saved it’s not the end of the world.

Andy

[Andrew CrowParticipant @andrewcrow91475]

Something I forgot to say earlier, I think Stuarts may be able to supply individual parts for this sort of situation.

[Neil AParticipant @neila]

Stuarts due supply spare parts in the event of an unsalvageable error. The con rod comes out at just over £30-00 including postage. I shall proceed with caution and remember to mark it out before cutting metal. If I do make a mess of it, I think that I will just go for a built up rod. Steel for the shank and little end and separate brass for the big end. There are a number of videos on the internet of this being done. More like full-size practice.

Neil

[Andrew CrowParticipant @andrewcrow91475]

At that eye watering price I’d totally agree 👍

Andy

[Mick BaileyParticipant @mickbailey28509]

If anyone needs some parts I have these that came with a box of lathe tools 35 years ago. They look like 10v.

 

[Author]

Posts