B J Cicada engine

[Petit]

Ok back from the dead it may seem! Cannot believe its been nearly 2 years since i started this project, where does the time go!? Anyway as you can probably guess i've had some lulls in productivity mainly due to motivation but also im building it at work so i can only work on it when time permits.
Anyway it is almost finished now and here are some progress pics:

Ok first thing, the propeller taper lock and washer was completed, purchased a propeller and stuck it all together:

Then i went on to make the carburettor components, hose tail, venturi body and gland nut

They were fun to make on a full size Colchester lathe but i got there!

Next was the carburettor body, i made this from aluminium round bar and machined the centre part square.

I then made the needle valve from 2mm steel rod, ran a thread up it and ground the needle untill i got a concentric point on the end. Put it all together and ended up with this:

The drawing called for a ptfe gland seal but it was impossible for me to make so i used sum suitable sized cable insulation which worked perfectly! :thumbup:

I did actually remake the carburettor body in the end as the wall thickness of the threaded part was way to thin.

 

[Petit]

.... More pics to follow when i get a chance

 

[michael-au]

Nice work on an interesting little engine

 

[Petit]

Ok so after the tricky carb build I then moved on to the steel cylinder, was a reasonably straight forward piece to make, hardest part was cutting the bevels on the fins.

Once i had completed the cylinder i moved on to the brass cylinder top cap and tommy bar,

Next on the list was the con rod, for the first attempt i decided to make it by hand this didn't turn out aswell as i had imagined so i decided to carefully mill it out and finish it off by hand, much better idea! :thumbup:

I fitted the conrod and tried to turn the prop but found the conrod was fouling on the bottom of the cylinder and locking up, i then remembered another member told me that it is an error in the plans and there is supposed to be two slight bevelled reliefs on opposite edges on the bottom of the cylinder, once i put these in the conrod cleared nicely.

The next job i was kinda anxious about.. silver soldering the carb boss to the cylinder, ive never really silver soldered before let alone silver soldered really small stuff! I did some research and with my new found information I went for it, didn't even go for a practice run. Luckily it came out absolutely fine, I made the decision to use a propane torch rather than oxycetaline torch as I thought it would be abit to fierce and could damage or distort some of the parts. Unfortunately the propane torch was the complete opposite and didn't have quite enough beans and took ages to get enough heat into it. Eventually i got there, the cylinder was completely blackened and was sporting some big blobs of solder but some careful cleaning up and it was as good as new!

 

[michael-au]

Looks fantastic, well done

 

[fishy-steve]

Looks the business!
Looking forward to seeing the video of it running. :thumbup:

 

[werowance]

looks great, I have attempted this engine with failure, I would really like to see pictures of the inside of the cylinder in particular the intake port milled into the side of it please.

cant wait to see yours run.

thanks

 

[Petit]

Thanks for your kind words everyone. I have now completed the engine, managed to make a barrel lap and lap the cylinder to what i feel is a good uniform finish,i think i went down to about 20micron diamond paste (started at 40micron), any less than that n ill be polishing it. Managed to lap the piston to within .02 of a millimetre to the cylinder and made the contra piston to the dco method, cutting a taper of 0.5degree. Really impressed with the fit, very tight to move by hand but easy to move via the tommy bar. So hopefully if all is well it may run on its first set of pistons! There will be pictures to follow, Werowance i will take photos of the cylinder for you.

Anyhow, does anybody no the correct way to start these engines?

I have no experience with anytype of model aircraft engine let alone a diesel one. All i know is that it turns anti clockwise.

Any help before i attempt to fire it up would be great!

Many thanks
Joe

 

[Petit]

Ok im struggling to get the tapered collet and prop driver to hold tightly on the shaft, i cant tighten the propeller up sufficiently. Has anyone got any ideas? Are there any tricks to making this sort of propeller mount assembly?
Cheers

 

[fishy-steve]

Hi Joe,
I haven't got the drawings in front of me but from memory the inner collet butts up against a shoulder on the crankshaft. So as you tighten the prop nut up the prop driver is driven up the split inner collet and locks up.
Did you cut the tapers of the collet and prop driver at the same setting ?
Have you split the collet ?
Is the front bearing housing .005" shorter than the crankshaft length to the Shoulder?
Hope this helps,
Steve

 

[Petit]

Hi Steve thanks for getting back to me, i did wonder if it was supposed to butt up against the front of the housing, i tried that but it locks up the whole thing, i guess you the have to spin it to get the brass or alu to wear down until it frees up?
The problem im getting is that i can get tapers to lock but it doesn't seem to tighten up on the shaft. The tapers have been cut to the same angle, although i have plunged the d-bit slightly to far into the prop driver so the bush goes in further but there is still some of the tapered collet sticking out to butt up, whether its enough or not i dont know?
I was wondering if i am supposed to drill the hole in the brass taper size smaller than the shaft and then slit it? At the minute ive drilled it the same size as the shaft and then slit it.
Cheers
Joe

 

[werowance]

there is a lip on the crank shaft that protrudes out of the bearing housing just a hair, the brass wedge butts up against that to tighten, not against the aluminum, now, you may have plunged the dbit a bit to far on the prop driver thus the prop driver is extending completely over the brass wedge? if so take a lill bit off the prop driver where the wedge goes in, should be good, but if the brass is butting up against the aluminum bearing housing, or "snout" as I was calling it, then either the shoulder on the crank isn't long enough or missing, or the snout is to long.

 

[werowance]

first picture, is the crank, circled is the lip that should just stick out through the snout, second pic is the snout or bearing that I'm talking about

dose the lip on the crank protrude out further than the tip of the bearing snout like the second pic? if so then probably went to deep with the dbit on the prop driver

 

[fishy-steve]

Hi Joe,
That's the shoulder I was trying to describe. It should protrude .005" beyond the front bearing housing. The collet then butts to it. I think I reamed the collet to size then split the collet.
Steve

 

[Petit]

Ah haaa yes thats it! Thats where i've gone wrong. For some reason i dont have that shoulder, now need to see whether ive made the front bearing to long or the larger shaft diameter to short. Ill report back. Thanks for your help guys!

 

[Petit]

Ok i'm back,
Just dropping in to show you all the finished article, it has been finished for some time now but i haven't got around to publishing it on here.
I'm extremely pleased to say that it runs! I only had to make 2 extra contra pistons trying to get the fit right, until i couldn't really go any tighter with it and that was all i had to do.
I followed some instructions i found online about starting these engines and basically it was just trial and error, increased compression to about 3-4 turns from max, and placed drops of fuel straight into the exhaust port. I found that i got more life out of it when i chucked more fuel into it and turned it upside down to swish the fuel around. I guess by turning it upside down you are using the oil/fuel to seal the faces internally.
After many times putting drops of fuel in and turning it upside down etc i finally got it going! Originally i was using a 9x9 prop, the engine ran but quite slowly as the prop was quite torquey, i switched to a 8x4 prop and now it runs very well. Anyway i've now got the knack to starting the engine and can get it running it very little time now and it runs well.

I made a fuel tank from one of those Vapeing pen things which turned out to be absolutely ideal, it even has a measuring scale on it. Only downside is that it would be better if it was slightly larger.

I then made a stand for the engine for display purposes using 4 posts made from brass and an aluminium base, and I also made a mount to run the engine on with the fuel tank fixed in position made from aluminium angle.

I then polished the engine, made a nice wooden base out of walnut and lacquered it in a low sheen lacquer and purchased a mice wooden pop for it for display use. Im really pleased with this engine, i didn't enjoy the machining as much as my other models but definitely preferred running it. Its actually quite addictive!

Here it is with the other models i have built sofar:

And here is a link to it running....

[ame]https://www.youtube.com/watch?v=pjbybRS14gI[/ame]

Hope you enjoy! Now what shall i make next!? hmmm

 

[fishy-steve]

This is a timely post. I dug my BJ Cicada engine out last night. Thought I'd give it a whirl. Mmm. Would only run for a maximum of 5 to 10 seconds ?
Anyway, I like the way you've set yours up for display. I especially like the wooden prop.
Great job.
Steve.

 

[werowance]

5- to 10 seconds you say, beats mine. I got like one pop out of it ever....I need to revisit and work on mine again to see if I can get it to run.

 

[Petit]

Thanks all! Werowance i would advise giving it another try, alot of it is trial n error. I was only getting short bursts out of mine to start with. I literally spent hours just flicking the prop trying to get it going but i basically didn't have the settings in the right place and not enough fuel. Did you try putting fuel in and turning it upside down? That worked for me. In these instructions i read it did say some models have to be started upside down n then righted once running.