Kiwi Mk II

[Eccentric]

Great looking piston. I can read the word "balanced" in the finish of the piston in the last pic. Nice lathe work.

 

[Richard P]

Great looking piston. I can read the word "balanced" in the finish of the piston in the last pic. Nice lathe work.

Thanks! Yes, pleased with how it came out for a first attempt. Not quite so shiny now but it’s been going up and down test fitting it in the cylinder for a bit!

 

[Richard P]

This week I have been working on some of the 'shiny bits' namely the oil reservoir and breather assemblies. Relatively straight forward turning and threading jobs, but quite a lot of them! I adjusted the design of the oiler so that it mounts directly on to the engine bearer. Hopefully engine vibration wont be a significant issue.

I think because some of the dimensions are not that critical, I got a bit casual, and so made a few errors along the way. A few times I got to experience one of my least favourite aspects of machining.... remaking the same part multiple time over!

 

[methuselah1]

Nice work! Nice to see curves, too... When I make these sort of items (on my engine, the float bowl cap, and the oil and fuel adjustment screws) I always dish the faces with a radius form tool- like the thumbwheels on old microscopes! The "fart valve" cover was too small for that, so I domed it instead...

 

[Richard P]

Nice work! Nice to see curves, too... When I make these sort of items (on my engine, the float bowl cap, and the oil and fuel adjustment screws) I always dish the faces with a radius form tool- like the thumbwheels on old microscopes! The "fart valve" cover was too small for that, so I domed it instead...

Thanks! I agree that the little details are worth the effort. I like the idea of some extra dishing and doming, so will bear that in mind as I proceed further.

 

[methuselah1]

It appeals to me, though I suspect I might be a frustrated steampunk...

 

[Richard P]

I've been working on the Con Road. The central linking part of the casting was a bit crooked relative to the bearing surfaces and so the sides have come out a little bit wonky! Overall though, after a bit of fettling, it's a very smooth running fit on the crankshaft big end bearing

.

 

[Richard P]

I thought I'd have a change from all the fiddly bits, so have been working on the flywheel. Nice to have a bigger chunk of the engine complete! I have also made the tapered collet but have not shown that here as yet.

 

[Mike Ginn]

And here are the valves, guides, collars and collets. I had a bit of bronze spare so upgraded the collars from MS for a bit of bling. First attempt at machining valves, so pretty happy with how they have come out. And they seem pretty air tight in their seatings even before any grinding, so all quite positive.
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Hi Richard
I am about to start the Kiwi build and have a new set of drawings from Hemmingway although the castings and now rather faded drawings were purchased about 20 years ago (don't ask!)
Have you found any drawing errors or dimension errors?
Thanks in advance
Mike - Chelmsford based

 

[methuselah1]

I didn't consider the cylinder casting useable, as it was undersized. I think Richard found the same thing. So knowing the Kiwi has a reputation for running hot, I made a fresh cylinder muff from HE15, and had it anodised black before skimming the o/d to finished dimensions, to give cosmetic contrast.

Further down the line, after making the rockers (which I put off as long as possible!) I found the exhaust pushrod could foul against the cylinder- I had heard of other builders who had found this.

I simply did a bit of careful clearancing work on the uppermost three fins, with a ball nosed mill to alleviate the problem; it'll be interesting to see if Richard finds the same is necessary on his engine.

The cams, as shown in the drawings, are a good approximation, but not the ultimate solution. I'm sure Richard will share his spread sheet for making better ones.

the points specified are (now) pretty obscure, but I paid a pretty penny and obtained some. There was no way they were going to fit on the casting! Options have been discussed here for alternatives, or you could pinch the simple design used on the Whippet engine, which can be found online. The supplied casting was very brittle and delicate, so I'd suggest milling one from bar stock, instead of trying to use it, to save frustration. I broke two castings.

Andrew UK

 

[Mike Ginn]

Thanks Andrew - I'll mark up the drawings to check when I get to those parts. I've just finished a Wyvern and now have the time to start planning the Kiwi build, noting the capacity of my available machines . (Myford S7 with dro, Warco mill with dro, small cnc mill etc). I guess I will follow the build order of ETW so it's front casting time!
Mike

 

[methuselah1]

Mike, you've just reminded me! I drilled the 3 and 9 o'clock stud holes and reamed them to accept 5/32" hardened dowels; that way I could firstly split the case halves as many times as I wanted, secondly ( and more importantly) I could put parallels beneath them and wobble off 'em as a reference for getting the top face the right height (and square), and get the cylinder studs in the right place...

My dowels are still in, I might leave them in; but I tapped M4 beneath the reamed holes so I could still fit "false" studs eventually.

Andrew UK

 

[Mike Ginn]

Andrew
Thanks for continuing to think of the issues. I always find that asking how others did the machining is of great help. There are a few YouTubers I follow and you can often pick up hints which all go into the pot - actually into a folder on the computer.
The studs seem like a great idea
Thank you
Mike

 

[Mike Ginn]

I would welcome the collective view on my proposed approach to the Kiwi crankcase bearings. The drawings call for an interference fits for the plain bearing and the ball race. I really dislike this approach in small brittle Al castings of unknown quality. I am proposing to do the following:-
Machine the bearing bores in both crankcase halves to a reasonable sliding fit plus 0.002(ish). I would then Loctite (bearing loc) the plain bearings with a drill rod in place and the halves bolted/dowelled together. I would then Loctite the ball races in place in a similar fashion but at a latter date to avoid swarf getting into the races. The Loctite would need to be correctly applied and my usual practice is to grove the bore or bush.
I think this would be an easier and less risky approach with a fragile casting. What are your thoughts.

Would ETW have used Loctite?. Interesting question - but it wasn't available when the design was published for the second time in 1960

Thanks for your comment in advance
Mike

 

[methuselah1]

Hello again! I went for a light press fit; I can't remember if I cooked the castings in the oven before fitting the races or not...

Either way, there is so much support from the front face, you'd need to be completely ham-fisted to split the casting. Half a thou shy of 7/8" should be ample. DROs or not, using a lathe made in 1941 meant that boring to this accuracy was quite daunting, but I did have very good measuring tools, and a trick up my sleeve...

I set my topslide to 6 degrees. That done, one thou of advance of the topslide progresses the tool one tenth on the X axis; it's an approximation, but not a bad one, so all was well.

On a different note, whenever I build an engine, I buy "proper" drawings which I copy for workshop use; in the case of the Kiwi, I had the magazine articles. I wasn't worried if they got oily (they did!), and I annotated them as I went... Angles, errors, everything- as you progress, tell me the part in question, and I can scan across anything that I made a note about, if you wish.

Andrew UK

 

[Mike Ginn]

Andrew. Thank you for that kind offer. I have a set of drawing sheets and I have cut each component out and placed them in plastic pockets - mainly to make the drawings manageable (Original is A1 size). I like your 6deg trick - hadn't thought of that. Although I didn't mention it in my earlier posts I have previously found that using a plug gauge (undersize) to assess the bore diameter can be an issue as it can become stuck!
So I am still thinking of the Loctite approach
My measuring tools are a set of Moor & Wright internal telescopic gauges and digital micrometer.
Thanks
Mike

 

[Richard P]

Hi Richard
I am about to start the Kiwi build and have a new set of drawings from Hemmingway although the castings and now rather faded drawings were purchased about 20 years ago (don't ask!)
Have you found any drawing errors or dimension errors?
Thanks in advance
Mike - Chelmsford based

Hi Mike,

Good luck with building your Kiwi, I've enjoyed the process so far!

Judging by Andrew's answers already, he took a much more methodical and annotated approach to his build, so I'm sure he will be able to share many pearls of wisdom as you proceed. I'm sure you have already seen Vince Cutajar's jars post which is a very step-by-step record of his build. I have found that extremely useful and he has carefully chronicled any difficulties that he encountered with each part, including any modifications to measurements. I followed Westbury's magazine sequence, but often used Vince's approach to each component as they were very well set out and made sense to me.

I confess that I sometimes focus a bit more on speed of progress than the absolute accuracy of every dimension. I am very careful in nailing the critical dimensions of an individual part, but then am a bit more relaxed at tolerances for some of the less important aspects, or where there is a bit of license to change the design a little for aesthetic effect.

I did find the cylinder jacket casting smaller than spec, but persevered with it, adjusting the dimensions of the fins a little. The supplied cylinder liner cast iron was also under spec but again I worked with it and adjusted the recess in the cylinder head slightly. I haven't yet worked on the ignition timing casting but it is pretty feeble, so will probably make something from bar stock. And I didn't like the supplied float chamber casting so have made that out of brass which looks quite attractive. I have not yet decided whether to go for a fully functioning float chamber design or convert it into a small fuel tank as Vince did.

Cheers

Richard

 

[Richard P]

This week I've been working on the carburettor, which has a lot of awkward parts. It will be the first time I have made one, so fingers crossed!

 

[methuselah1]

Nice work, Richard! I fabricated mine- nothing wrong with the casting, but I got to use brass against copper, for "bling"! I also made a brass float bowl, for the same reason... I made my tank from some 1+5/8" copper tubing that started life as the outside waste pipe from my Dad's kitchen sink; (and people wonder why I never throw stuff away?) so by the time I'd made a pair of spun copper end caps, a brass filler, and an outlet and stop valve, it looked OK, and it was fun to make.

What are you going to do for the jet screw needle?

-Andrew

 

[methuselah1]

Any pearls of wisdom that I can provide may be the result of cracking many oysters full of ****-ups... Which you won't hear so much about...

At least some of the time, that will be why I made notes in the margins. After sequence planning, there is nothing particularly methodical in the way I go about making stuff!

-Andrew