Nemetts 15cc engine

[wheeltapperParticipant @wheeltapper]

deleted, double post.

Edited By wheeltapper on 30/08/2011 21:41:28

[wheeltapperParticipant @wheeltapper]

Steve

I just looked at your pics of this engine and noticed you don’t have a breather pipe to the cam box.

 

is that only necessary on the petrol version?

 

Roy

[wheeltapperParticipant @wheeltapper]

Hi

bit more done.

piston rings made and fitted and con rod made and fitted with bearing.

more soon.

Roy

[Steve WithnellParticipant @stevewithnell34426]

Hi Roy,

 

Don’t think the glow plug version needs the breather, I didn’t accidentally omit it and I’d never made an engine before, so I will have stuck to Nemett’s article to the letter as I had no experience to rely upon. I did put a couple of drops of oil in the cam housing before I started it up and after that there was plenty of oily smoke every where!

 

You are doing a cracking job of this – you can’t avoid the head much longer! Just keep measuring twice, checking twice and cutting once and it will come out just fine!

 

Steve

[Steve WithnellParticipant @stevewithnell34426]

One thing I do remember from the build which I did forget, was that Nemett recommended the use of a split pin to retain the prop nut as he’d had his prototype backfire and kick the prop off. I simply used a nyloc nut. I didn’t experience the engine kicking back on the few occasions I ran the engine, so maybe the timing on mine was slightly off.

[wheeltapperParticipant @wheeltapper]

Hi

I remember reading about him nearly scalping himself.

he recommended a circlip but I was giong to use a split pin.

 

I couldn’t figure out how to do up a nyloc nut without holding the shaft somehow.

 

stop press!!! I’ve started on the head.

 

so far I’ve done the valve holes and the fixing holes from the underneath, and turned it to finished depth.

 

I splashed out on a rotary table, very handy gadget.

 

Roy

[Ramon WilsonParticipant @ramonwilson3]

Roy, Steve,

Speaking from personal experience a prop continually loosening or indeed spinning off all together is definitely not ideal.

 

Personally I think the circlip idea to prevent total ‘loss’ is better than the split pin if for no other reason than asthetics though either could catch an unwary finger if run exposed. A split pin will have to be continually straightened for removal too. However niether will actually prevent the prop from loosening as it fires and kicks back which is the root of the problem.

 

Though I have no experience with them directly I know model four strokes have a far greater propensity to throw a prop than two strokes but it happens with these quite often too.

 

When flying/competing in C/L aerobatics there is only one minute allowed to start and

get airborne. A loose prop in that situation then is a definite no-no.

 

I found that introducing a paper ‘washer’ cut from 240/320 grit wet and dry between the driver and the back of the prop (grit toward the prop) virtually eliminated this problem both on wooden and ‘plastic’ props. On some aircraft there was the need to space the spinner backplate out from the prop driver to clear the fuselage and these spacers were made from nylon. Again wet and dry washers were used between all surfaces with total success.

 

It’s a simple tip but works well certainly worth trying to see if it will do the same in your situation.

 

Small, short, drive peg/pegs can also be incorporated into the driver to match a shallow hole/holes in the prop but a paper washer is much easier to produce

Like wise by drilling a radial hole in the prop driver to accomodate a ‘tommy’ bar when tightening the prop nut if you decide to use a nylok – though it’s hardly likely to cause an effect, by drilling two or three the balance remains and is more asthetic.

 

Hope this is of use/interest

 

regards – Ramon

 

 

 

 

 

 

 

 

Edited By Ramon Wilson on 05/09/2011 09:49:16

[wheeltapperParticipant @wheeltapper]

Hi

a bit more done, the cambox.

its coming along, bit by bit.

 

Roy

[Steve WithnellParticipant @stevewithnell34426]

Hey Roy – you avoiding the cylinder head? I can see all the parts getting done, except the head!

 

Steve

 

 

[wheeltapperParticipant @wheeltapper]

Hi Steve.

Not really, I’ve drilled the valve and bolt holes and turned it down to the correct height, I’m waiting for some milling cutters to arrive so I can counterbore the holes then I can get on with the rest of it.

I’ll keep you up to date with pics as I progress.

 

cheers

Roy

[wheeltapperParticipant @wheeltapper]

HI

are you still watching Steve, I’m not avoiding the head any more.

 

top

bottom

and finally

all dressed up

 

I just need some phosphor bronze for the valve guides.

 

when I recover from doing this I’ll have a go at the camshaft, cutting the cams should be fun, I’ll need a “do not disturb” sign.

 

Cheers

Roy

[Steve WithnellParticipant @stevewithnell34426]

Very nice indeed! no sign of any “oops!” unlike mine!.

 

I can hear a 4 stroke burble coming on soon…

[wheeltapperParticipant @wheeltapper]

there are a few near oop’s’s .

for a start the inlet hole is 6mm instead of 7.5 because it was too close to a bolt hole,

 

I sweated a lot tapping the last 4 holes for the exhaust.

 

I had a go at the cams earlier, what a soul destroying job that was, my arm is killing me cranking the mill bed backwards and forwards 360 times.

 

stil, its all supposed to be fun……………………………………………………………….isn’t it?

 

cheers

Roy

[wheeltapperParticipant @wheeltapper]

me again

 

a bit more done, cams cut and fitted.

watch this space

 

Roy

[wheeltapperParticipant @wheeltapper]

Hi

I thought I’d stick it all together temporarily to see what it looked like.

 

behold the beast

cheers

Roy

[Clive HartlandParticipant @clivehartland94829]

Now for a nice bit of anodising Roy, The head in Red and the cylinder in deep Blue and the crankcase Black.

Very good work there Roy and you should be proud of what you have made.

It should run well!

 

Clive

[Steve WithnellParticipant @stevewithnell34426]

You’ll be needing a can of this soon!

 

Works everytime, honest.

[wheeltapperParticipant @wheeltapper]

Hi Steve

I hope it doesn’t come to that.

 

I had a good day today, I made and fitted the valve guides, cut the valves to length and put the e clip cut in.

after assembling the valves in the head I put the liner in the cylinder jacket and bolted the head on.

 

then I jammed a piece of soft plastic tube ( aquarium air line) in to the plug hole and fixed the other end to a small air compressor I have, it gives about 40 psi.

 

holding my hand over the bottom of the liner it blew the line out every time so I assume the valves are sealing.

 

the only thing holding me up now is the timing pulleys and belt.

HPC are out of stock of the large pulley.

 

more news as and when.

Roy

 

[wheeltapperParticipant @wheeltapper]

Well they say pride goes before a fall!

 

I thought I would make the timing disc seeing as I’m that close to finishing and I was idly twiddling the camshaft and it suddenly hit me with a thump that the cams were in the wrong positions.

however a quick dose of heat from a small blowtorch soon broke the shaftloks grip so I’ll do it again properly .

I would have sworn I followed the instructions to the letter, obviously not.

all I can say is ” what a prat”

a rather annoyed Roy.

[Clive HartlandParticipant @clivehartland94829]

Better than bent valves Roy, soon fixed I hope!

 

Clive

[Steve WithnellParticipant @stevewithnell34426]

Posted by wheeltapper on 04/10/2011 20:27:29:

Well they say pride goes before a fall!

 

I thought I would make the timing disc seeing as I’m that close to finishing and I was idly twiddling the camshaft and it suddenly hit me with a thump that the cams were in the wrong positions.

 

Steve:

 

Funny, I made exactly the same error!

[wheeltapperParticipant @wheeltapper]

Thats amazing, it makes you think that the instructions were wrong.

 

I’ll have a good look tomorrow.

 

Roy

[wheeltapperParticipant @wheeltapper]

Hi

I’VE FINISHED

and it runs

some pics of it ready to run,

here are some pics after I stripped, cleaned and polished it up a bit

I’ve got two videos of it running but I don’t know if they will work on here. they are on Photobucket at the moment but it looks like I can only use youtube here.

 

I have just started an account there and am uploading as I type this so I’ll see what happens.

 

watch this space.

 

Roy

[wheeltapperParticipant @wheeltapper]

OK how do you add a vid link,

 

Roy

Edited By wheeltapper on 14/10/2011 20:02:39

Edited By wheeltapper on 14/10/2011 20:05:46

Edited By Katy Purvis on 01/06/2015 11:37:32

[Clive HartlandParticipant @clivehartland94829]

Roy, what an excellent piece of work you have done! If it looks good then it must be good!

 

Clive

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