Cicada 1.3cc "diesel\2

I have recenty finished this engine and would like to hear from anyone else that has done so. Drawings are from the late Ron Churnichs Motor Boys site, found after talk on here regarding the Nalon Viper engine, from the same source. I am not sure if it is a real attempt at designing a usable engine, or, if it was an execise in making one from bar stock material only. It is heavy for its capacity, 195grams compared to 129 grams for the repro Mills 1.3cc that I made.. I thought the appearance looked a bit "brutal" to me ,so I have put some taper to the muff shape,thinned and rounded the edges of the fins,plus adding an extra fin. I also put some taper on the front bearing housing and added a bronze bearing The weight is in the all steel cylinder and fins being machined from one piece of EN1A.. It is unusual in having the fuel bypass opposite the exhaust, rather than at 90 deg to it and I think fuel is being squirted straight across and out the exhaust somewhat.. I found a major clash with the con-rod against the cylinder wall on one side. The bypass slot gives clearance on one side, but no clearance is drawn for the opposite side. I found I had to re-machine a 60 deg slice from the internal cylinder wall to allow the rod to clear OK. I have lapped the piston /cylinder to achieve that leak proof compression required,, but to date have only managed to get it to run is bursts of about 5 seconds after a prime, whatever I do with the carb. This shows it is onlty running on what is in the crankcase, so I need to do some work on the carb, made as drawn.. It has plent of suck, so I think my next move will be to fit the Mills carb to it, as I know that works.I made the stub theads the same for this purpose .Keith

hi keith

what do i know about these diesel engines not a lot but when i had a mills 0.75 more years ago than i choose to remember it would not start some body said try a bigger prop and it went straight away

geoff

Hi Geoff,

I will certainly try that on my next session. Thanks

I am reluctantly coming to the conclusion that I have made a pretty paper weight.! I have been using,making and re-furbishing model engines for many years and this is the first one that I cannot get to run. I have spent quite a few hours since the last posting, re-checking dimensions, using every trick I know regarding starting a diesel, all with no better result that I got at the first attempt to run it. I have put my Mills 1.3 in the test rig, using the same fuel,carb and propellor and it started 3rd flick after a prime. To check fuel is getting in the upper cylinder,I removed the head and contra-piston. Fitted the Mills fuel tank, put it in the lathe ,at 25 RPM and watched with a torch to see if fuel is actually coming through the by-pass and it was. There is a limit to the time I can stay interested after flicking a prop for an hour and just getting a burst for a few seconds, whatever I do. I had hoped by now that some one would appear who has also made this engine. The one thing that I thought was odd with the design, was the position of the by-pass opposite the exhaust, when there is no reason for it not to be in the front,as is usual. The by-pass being so positioned, means the channel is also used to give clearance for the swing of the con-rod and I wonder if this is upsetting fuel flow?

Since the previoius posting I have spent more fruitless time trying to start this engine. I then had the idea that if I was having to turn it into an ornament I might as well try machining an additional fuel bypass in the front of the cylinder, where I have always thought it should be. If it does not work after that then I am no worse off. That has turned out to be my decision of the month as back on the test rig I had it starting easily after finding the compression setting. I have had two 4 minute runs at 4500 RPM so far, with a short burst at 5800 RPM and I am happy at that.

Clearly ,the position of the bypass, as drawn,is incorrect and I advise any other maker to machine it in the front position. The fact that the con rod oscilates in the same space in all probability was interfering with the way mixture was getting into the upper cylinder Having two bypass ducts does not seem a problem.

I have a picture of it running and have been trying to put it in my album for the last hour. I always have trouble putting pictures on here as I cannot find an "export " button to enable them to be moved, then suddenly, sometimes it works and I am not sure what I did to make it work. Wish it was as simple as drag and drop!

Photo of the Cicada running at last

Good to hear that its running at last, now you will have to make something else to keep your papers in order.

Thanks Jason,

I was hoping some one would comment on how fuel behaves when being transfered by crankcase compression. or that they had made this engine. Cannot believe I am the only one to do so.

Keith.

Keith, a mate of mine (Ed Holly) just finished his Cicada and it seems to run nicely Ed's Cicada

Maybe you could swap notes.

I am currently building a Sparey .8 diesel after I discovered the plans in this lovely ancient edition of Aeromodeller magazine Aeromodeller May 1947

IMHO we should all count ourselves lucky that we have our hobbies to help keep our sanity during these difficult times.

* Danny M *

Hi Danny, That is agood idea to swap notes.I have seen the vid of Eds running from your link. Is he on this Forum? I notice on that vid link that Chris Boll ,the designer is mentioned. Is he contactable? I am in UK and it sounds as though you are in OZ. I have recently finished the Sparey .8, wwhich is really .6cc. Photos are in my album under Chenery VEE TWIN. It runs very well. I also made the 5cc version several years ago.

I share you thoughts about our hobby.

Keith

Chris is an occasional member here and I'm not sure if the Rod Jenkins mentioned is Roderick on here who is a bit more active on MEM forum as "Tangler"

jason , I am a bit confused about the mention of Rod Jenkins?

Keith

opps it was Rob not Rod on th evideo.

Danny, I have put amessage in your box,.

Keith