Plunket Jr. Build

[swilliams]

Nick, I'm planning on just seeing if I can get the engine to run. Being new to this IC business, if it runs I'll be very happy.

My lathe is also limited to about 700rpm, which I use alot for small stuff, brass and drilling small holes. I mostly use cobalt hss for turning, it's easier to sharpen than carbide Many indexable carbide tips won't get a good finish with light cuts, so it might not just be the speed.

Steve

 

[swilliams]

So over the last day or so I solved one of the problems I've been struggling with. In the plans the inlet valve assembly is housed in a part made from a bronze elbow. I was having trouble finding an elbow I was happy with. Anyway I got over the problem with some machining and a whole lot of filing.

Being well and truly over chasing up stuff I started with a bit of brass cut off from some 1.5" stock I already had. The diameter I started with was way too big but I was making this plan up as I went.

Then I did some rough milling and some turning to get a starting point before busting out the files

 

[swilliams]

So here's how it's shaping up. The plate will be used to bolt this assembly onto the back of the cylinder assembly. I still need to cut out its outside profile with a piercing saw.

So after some filing

and the final product

Steve

 

[Maryak]

Steve,

Been lurking - great work. :bow: Like Arnold I wondered about the valve springs. As you say only the free end compresses. Wonder what that does to the spring characteristics. Someone with better math skills than me may offer an explanation, (that's about 50% of the world population).

Best Regards
Bob

 

[swilliams]

Thanks Bob

Presumably you had some decent mathematical skills when you worked out that 50% of the population stuff (joke)

The part of the spring that is jammed up on the taper does nothing so it's as if it's been cut off, making the spring in effect about half as long as it appears. If you halve the length of a spring then the coils have to move twice as far when the valve moves the same distance. So assuming the spring is linear (which it will very close to) the spring will be twice as stiff.

Steve

 

[Maryak]

The part of the spring that is jammed up on the taper does nothing so it's as if it's been cut off, making the spring in effect about half as long as it appears. If you halve the length of a spring then the coils have to move twice as far when the valve moves the same distance. So assuming the spring is linear (which it will very close to) the spring will be twice as stiff.

Steve

Aha

Thanks

Best Regards
Bob

 

[NickG]

Very professional looking Steve,

One day I hope I can turn out this sort of work.

Nick

 

[swilliams]

Thanks Nick, you are also doing some very nice work. Anyway I think we're both having fun building stuff which is the main thing.

I've been building the oiler. Started with an insect repellent cap to make the transparent tube

acrylic tube would have probably been better but I couldn't be bothered chasing it up. Anyway I cut the ends off by jamming it on a bit of steel that had a matching taper turned on it

Here's a shot of drilling a hole through the top cap for filling. I screwed the cap onto a bit of wood and my pinkies remained unscathed

Next, putting the knurl on the flow adjustment knob

Here's how it looks on the engine, still a couple of little bits to go on the oiler but it's nearly there. You can also see that I 've got the exhaust valve mechanism sorted out

Next major part to build is the carburetor. Waiting on some reamers for that one, if they don't arrive I'll make the radiator first.

Cheers
Steve

 

[NickG]

These sprays are good for model engineering material! Our sun cream no longer has the plastic cap, that was used as the displacer cylinder on my tiny stirling engine!

Lubricator looks great on the engine. ;D

 

[swilliams]

Thanks Nick

Indeed the spray caps can help you out of a pickle ;D

 

[swilliams]

I apologise for not posting on this for some time. One way or another I've been very busy with work and stuff.

At any rate I manged to make the carby and the ignition. For the ignition system I used the hall effect system with coil from J. Howell's site. The coil is the one on the top of this page, http://www.model-engine-plans.com/partskits/ignitionsystems/coil.htm
The spark plug is just a little Honda one with a 10mm thread.

The good news is I managed to get the engine to run for a sustained period. Eventually I switched it off because it was getting hot and I don't have the water cooling system made yet.

The bad news is it is still very difficult to get to run and when it was running it ran super rough.

I have two thoughts about what to try next to improve how well it runs

1) I used 4 AA batteries to power the ignition at 6V. The spark was a decent blue colour but it seems rather small. I'm thinking I might get a stronger spark with a larger battery. I have very little experience at this, so the question. Should it run properly with 4 x AA batteries or are they too small?

2) The second thought is I could probably improve the lapping of the inlet valve. The engine seems to kick back like a mule when I try to start it though. Seems to have good compression.

Anyway I'm keen to hear some suggestions. I'll try and get some pictures soon :-[

Thanks in advance
Steve

 

[steamer]

Hi Steve,

Congrats on getting her running!....My first impression of the issues is it's not the valve...kicking like a mule tells me the valve is tight unless it is also backfiring?. It might be it's timed too early? Additionally, I would suggest a hotter battery set up with more current available. Like a great big 6V lantern battery....JMHO

th_wwp th_wwp th_wwp th_wwp ;D

 

[swilliams]

Thanks Dave

"Like a great big 6V lantern battery" Now that's what I wanted to hear. I just need to get down to the shop and buy one. I'll attempt to do that at lunch tomorrow. Promise some pics next time I make it to the shop. Hopefully tomorrow evening.

Cheers
Steve

 

[NickG]

Excellent new Steve, can't wait to see it. 4 x C or D batteries would probably do the trick? if you find it hard getting the lamp battery.

Nick

 

[swilliams]

Hi Nick

I managed to get a lantern battery at lunch. Could only get it with a torch (flash light) which I immediately tossed in the bin.

Anyway I'm planning some more experiments tonight. Stay tuned

Steve

 

[swilliams]

Well I got it going with the lantern battery. Here's the video (hope it works)

http://rsc.anu.edu.au/~swilliams/movies/MVI_0848.AVI

Anyway some observations.

1) The coil and ignition kit from the J. Howell site have performed very well so far.
2) The engine seems surprisingly powerful. It gets up to an alarming speed when the throttle is opened up. The video doesn't do justice to the amount of noise and the speed it runs at when you see it in the flesh.
3) I'm having trouble with the engine running too rich. I think I need to make the taper on the carby needles finer. Other than this, things seem really good

Finally some questions for those who know more about such things than me (wouldn't take much ). So far I've just rigged up a makeshift system for the fuel delivery. Seems to me the height of the fuel in the fuel tank must be below the spray bar in the carby; is this correct??? I'm planning on making the fuel tank out of some 1.5" diameter brass tube which I will position horizontally. That means the height of the fuel will change by 1.5" when going from full to empty. Will this have much of an effect on the fuel mixture. i.e. will it lean out when the tank gets towards empty??

Thanks in advance for any replies to my questions.

Steve

 

[cfellows]

Sounds and runs good. Nice job! :bow:

Chuck

 

[NickG]

Brilliant stuff Steve, looks and sounds really powerful. A rare beast you've made there.

Nick

 

[joe d]

Steve

That's just excellent! Sounds great, and looks really good.
Glad to have been following along. Sorry I can't help much
with the questions.....

Cheers, Joe

 

[coopertje]

Congratulations Steve, very well done and runs very well. :bow: its a beauty!

Already plans for a new project?

Regards Jeroen