A Robinson from rejects.

[Ian j]

"That's looking nice Ian, good to see how parts can be made in different ways if we opt out of using castings"

It may take longer to machine a part from bar stock but  I think that out weighs the time taken in holding and positioning awkward shaped castings. Plus it's very satisfying turning "scrap" into machined engine parts.

[Jasonb]

It may take longer to machine a part from bar stock but  I think that out weighs the time taken in holding and positioning awkward shaped castings. Plus it's very satisfying turning "scrap" into machined engine parts.

I was thinking just the same while making that gear, had I used the casting I would just have had to face off each side but the amount of work in cutting the gear from solid far out weighs that, gave me some new challenges and at the end of the day was 100 times more satisfyin.

My eccentric strap will be coming out of this disc that went into the scrap box with the "rod" from a bit of bar.

[Alyn Foundry]

You guys are amazing!

It just shows that with both time and patience the near impossible becomes reality.

Very well done.

Cheers Graham.

[Jasonb]

I found that photo of how I locked the spindle on my X3 mill



So with the gear made I thought I may as well do the rest of the gearbox. The simple iron casting for this was one I was given by mistake so thought I may as well make use of it so cleaned up the spigots and turned to finished OD and finally parted off a 1/16" slice to form the cover.



I opted for a different machining sequence to Graham and started by drilling and tapping the two holes and also spotted the position of the crankshaft hole with the two parts clamped together



The remaining part was then turned down until the gear would just slip on with minimal play.



The cover was then screwed on and the spot mark set to run true in the 4-jaw before drilling and then boring the hole to a running fit on the spigots either side of the spur gear.



With that done the cover was removed and the central boss opened up around the hole so the gear could slip inside



And this is how it fits together under the cover



Works too

<a href="https://www.youtube.com/watch?v=bKVMaQw4DVA" target="_blank">http://www.youtube.com/watch?v=bKVMaQw4DVA</a>

[RayW]

While waiting for the new gears for my milling machine ( which arrived today), I have been getting on with the gearbox, which is now complete apart from the hole for the locating pin. Next job is the eccentric strap, but I am trying to decide how best to machine this casting, as it is a pretty awkward shape to hold. I am not sure whether to do it on the lathe in the four jaw chuck or on the milling machine with a boring head.I would be interested to hear what others have done.
I also made the little oil cups for the main bearing caps today.

[Alyn Foundry]

Hi Ray.

Nice progress, that's the gearbox virtually finished.

As you remark the eccentric strap is an odd shape but all I used to do was hold it in the 3 jaw using a parallel behind it as a datum, gently remove parallel and proceed to bore out the casting to size. I never tried to bulk remove the metal but I wonder how a good quality hole saw might fare?

As a warning I had a couple that because of being a little heavy on the chuck key ended up 3 pointed, I learned to remove the bulk then slacken the grip on the last couple of light finishing cuts.

Cheers Graham.

[RayW]

Thanks for that advice Graham. I am pleased to say that the eccentric strap is now fully machined and assembled with the gearbox (see photos). Having taken the pictures, I have just realised that I have still not drilled the locating pin hole!

[crueby]

That's quite a mechanism, very well done!

[Jasonb]

Just like a Russian doll another part was stitch drilled out of the a disc of 10mm steel



Quick tap with a hammer and out drops the middle



The rod and a block for the oiler were silver soldered on and job done. I will leave the pin hole and tappet untol I can assemble the engine to get the position/size correct

[Ian j]

Looking good Jason. I had difficulty holding the oiler block in position for silver soldering on mine, I had it clamped but that fell off when the blow torch heated it all up. I think if I had drilled it through to the eccentric and pinned it I would have a neater joint Still learning by my mistakes

[Alyn Foundry]

Hi Jason.

Nice bit of fabrication!

Are they “ soft “ soldered? In fact I would approve as a “ good “ joint can be achieved without the necessity of using harder solders.

Ian, there’s an old saying.... the person that never made a mistake, never did anything.... The important thing is to learn from them, I’ve spent my whole life doing just that!

Cheers Graham.

[Jasonb]

Thanks Graham, They are silver soldered but there is a little JBWeld to tidy up the joint between rod & ring which may be the colour you are seeing. One of the problems with fabricating "on the fly" you don't always foresee the consequences of your actions.

[RayW]

Finished the connecting rod today. When first assembled with the piston, I found that the end of the little end block was fouling on the unmachined area inside the piston. so ground away some of the excess metal with my trusty Dremel to give adequate clearance to allow full movement of the connecting rod.
I opted to press fit the little end bearing with Loctite 648 for extra security. This was rather than the pinch bolt arrangement as shown on the plans. As drawn, there is a small oil hole in the bronze bearing which is intended to line up with the slit in the block, but as I was not using that method of holding the bearing, I drilled a hole through the block and bearing to provide a method of getting oil to the bearing.

[Alyn Foundry]

Hi Ray.

One less piece to make eh?   

I used to hack them out of the solid, used to buy 6 foot lengths of BDMS bar. Go to use Alex’s chop saw to make several big end caps and rod blanks. Then back home to the Harrison L 5 that’s fitted with a very handy taper turning attachment. Tedious but necessary when you’re building for a customer!

The pinch bolt was “ always “ dummied however.

Great progress, not much more to go!

Cheers Graham.

[RayW]

Tackled a job today that I had not been looking forward to - line boring the main bearings. Don't know why I was so worried as it was a relatively straightforward process once I had the main engine casting clamped securely and positioned correctly on the milling machine table. I set it up first using my smallest centre drill as a guide, and without the bearing caps fitted, ensuring that my scribed centre line was exactly vertical and that the centre drill was in line with the mating face between the main casting and the bearing caps.
I then fitted the caps securely and centre drilled, then used progressively bigger drill bits until there was just a small amount left to remove with a reamer for the final fit.