B.J. Cicada build

[werowance]

What sort of parting tool are you using? Is it a piece of HSS that you have ground to size and shape or is it one you purchased already made?

Usually the reason that parting tools walk is either it is being run at too high an RPM, the tool is not on centre or or the cutting angle geometry is incorrect, usually the clearance angles are too great.

Another thing to watch is that during the normal use of your lathe the compound slide with the toolpost on top can end up overhanging the dovetailed slide, which when you start using a tool like a parting tool can can cause vibration, if so reposition the compound slide so that it is fully supported. Also check the adjustment of the gibb strip on the compound slide and cross slide and adjust it for minimal play then take a cut.

When you are parting, being on centre is probably the most important thing, also try to make sure your tool is set square to the axis of the job.

If you are using a two or four way turrret style toolpost have all your tools matched with the correct size packing and keep said packing and tool as individual sets so that you can swap tools at any time and know that each tool is on centre every time. If you are going to set each tool up this way do it with a piece of material in the chuck and take a cut across the face if you are below centre you will end up up with a parallel nib in the centre of the job, if you are above centre you will get a conical tit and if you are on centre it will cut the centre off cleanly.
Rob.

it was a parting tool I bought in a "lot" of used bits on ebay. it was I believe a half inch piece of hss but looked factory ground to a parting tool. I took that and ground it narrower. the first 2 cylinders It cut really good with minimal chatter as compared to this one.

I believe my problem with vibration and chatter is on the first 2, I usually put my parting tool just a tad under center. but on this one I actually centered it to the point of my tailstock live center then swung it around and started cutting. I didn't lock the gib on my cross slide to way. and frankly my gib adjustment screws really needed a little snugging as well at the time.

so I think the vibration from cutter being to high along with gibs not tight caused the issue.

oh well, part doesn't look that bad hopefully it wont be noticed by my friends if/when they see it run.


also I am using a qctp axa size from phase ii. I need to get some more tool holders, just havnt gotten around to it. I have enough for my most common tools. but as this parting tool was ground just for these fins I had to swap out a tool in the holder and didn't think about going lower that dead center when adjusting it.

thanks for your help. hope to get some more shop time this weekend.

 

[werowance]

Little more progress. Cylinder 3.0 ready for lapping. Will take time to re read and study the lapping suggestions in this post before I go there.

Need a little cleanup on the brazing job but it's decent and will do
View attachment ImageUploadedByModel Engines1429484270.809156.jpgView attachment ImageUploadedByModel Engines1429484291.502526.jpg

 

[Billitmotors]

G'day Werowance
Your getting there, are you going to taper the fins?
You can remove the the excess silver solder with a Dremel and some of their rubberized abrasive points.
Also I don't know if it is just the photograph but that transfer port looks a bit shallow.
Rob.

 

[werowance]

I am probably not going to taper the fins, if my tool hadn't walked I could have gotten 1 more fin in like my others and that looks so much better but in this case if I can just get it to run ill probably call it quits on this engine.
on the transfer port, I agree it does look shallow but I centered my .250 mill in the center of the bore and then moved it .125 over like the plans call for. but honestly the original 2 cylindars were not properly measured the first go rounds so they were deeper.
ill give the rubberized grinding tips a try, would be easier that filing and sanding. thanks for that tip.

 

[werowance]

Wow billitmotors. A lap seems to work extremely well. I can feel the taper in the cylinder and can feel it leaving

Started with 7 micron lapping paste. I assume the smaller the number = larger grit size. My fingers just can't feel the difference. But looking at the pics. The fist one is after about 5 mins. Can't believe the pitting. Next pics are after about 30 mins off and on with a break in between.
The brass lap is working great. I can feel the taper leaving


So after about 30 mins I have a very small pit left at the top. Should I keep on with current grit till pit is gone or go ahead and stat working my way up in grit sizes?View attachment ImageUploadedByModel Engines1430602800.419095.jpgView attachment ImageUploadedByModel Engines1430602819.360273.jpg

 

[Swifty]

You will find that the smaller the number, the finer the paste. A micron is 1000 of a millimetre, so 7 micron lapping paste is finer than say, 14 micron paste.

I can see the confusion, as wet and dry paper goes the opposite way.

Paul.

 

[Billitmotors]

Gday Werowance
Your looking good I would continue a bit longer with the same grit and then make a new brass lap and change to your fine paste.
Looking at your photo's I think you need to traverse your cylinder a bit faster along your lap as I like to be able to see more of a crosshatch pattern in the bore.
Also try and leave a bit of taper in the bottom of the bore below the exhaust port, preferably at least .001 and try to keep the top section adjacent to the contrapiston as parallel as you can.
Rob.






'

 

[werowance]

after about 5 or 6 more contra pistons (ive lost count) I finally have one that is nice and tight, no blow by. its tight enough that at first I was a little concerned that the force needed to push it back out if pushed down to far might be to much for the little aluminum rod to handle. but after some testing I can push the contra back up if I over compress it with the screw without breaking anything.

tried to start it last night. only had about 15 mins to spare, but after about 30 to 45 seconds of spinning with a cordless drill the cylinder fins were getting good and hot just from the compression. I could put my hand on it but it never got hot enough to ignight. and of course murphys law when your in a hurry, the battery on your drill is never charged up good so I didn't get to spin it very long.

wonder how hot it should get before I start getting smoke or fire? maybe I should pre heat with a little plumbers torch before I try again tonight?

I hope this heat is a good sign.

 

[Billitmotors]

G'day Werowance
You shouldn't need to use the electric drill to start the engine. You are not trying to heat up the cylinder to make it start.
You should be able to get it to fire by flicking the propeller over even if cold.
It sounds like your fuel mix is incorrect or your compression needs to be increased.
Don't use your blow torch to preheat the cylinder especially if you have already put fuel in the engine, as it is very flamible and you could very well end up with smoke and fire.
The fuel mix that I use is 20% castor oil 30% ether and 50% kerosene.
If your piston and contrapiston are a good fit, your fuel mix is correct, and you have set your compression correctly, it should fire when cold or hot, even just turning the engine over by hand you should feel a kick.
Good luck
Rob.

 

[Jasonb]

And if you are using a cordless drill make sure you have it in reverse!

 

[werowance]

Morning all, last night I decided to give the little cicada another try after sitting in a box for almost a year with a broken rod.
so I made another rod and made a fake propeller out of a strip of wood that was a little bigger than the bough prop I was trying.

so I got to the point that I had some kick backs, a loud "ping" noise a few times like dropping a thin piece of steel on the concrete floor and some smoke / oil out the exhaust. lots of black/brown residue oil coating the case and some smoke out of the exhaust. but still would not fire up.

that ping scared me to death the first time then I realized it was just trying to fire.

I found that loosening the compression screw actually helped where I thought I didn't have enough compression at first I found that it would ping and smoke whith less compression.

I ended up after several hours and frustration breaking the rod again. totally my fault and stupidity.

but was wondering, those of you who have made this engine, how many screws out on the carburetor seems to work for you? example on a brigs and Stratton mower engine I usually screw all the way in and then back it out 2 and a half turns.

then on the compression screw lets say we screw it down just until you can feel the piston hit the contrapiston. then how many turns backward are you backing it off for starting?

Brian Runpow, I read that you made a venture sleeve or something on your carburetor? I never fully understood what you did there and was wondering if you had pictures.

I am using store bough tower hobbies diesel aero fuel. when I got close to it wanting to start I could smell the rich fuel smell sort of like trying to start an old diesel tractor in the middle of winter using lots of either. when that tractor starts it smells like either and rich diesel. so that was encouraging me to think I'm close.

and last but not least, if my next starting attempt fails, would any one volunteer to let me ship you my engine for a look over and tell me what all I did wrong on it? along with maybe a gift card for your favorite lunch restaurant

 

[Brian Rupnow]

Werowance--I have never built a compression type engine as you show here, but I have dicked around a lot with small carburetors. Sometimes, if a carburetor intake is too large for the engine the carburetor is on, the air flowing through the carb will not be fast enough to create sufficient venturi effect to lift fuel up from the gas tank. The answer to this is to build "sleeves" of varying diameters that are simply a "push fit" into the carburetor air intake. (This is not an exact science, so you have to try sleeves with different bores until you find one that works.) This makes the inrushing air to move at a higher velocity, creating more venturi effect to be able to suck fuel up from the tank.

 

[werowance]

ok, that makes sense, and should be easy enough to try, ive got some teflon rod that should make that job easy to test with.

thanks
Bryan

 

[fishy-steve]

Hi werowance,
I came across some great videos a couple of days ago of the correct starting procedure for ci engines. I really wish I'd seen these before spending hours trying to start my Cicada.
Having now built a couple of these types of engines I have a better feel for them and there is a definite knack to it that you can't really convey in words.
Search "Brian Cox engines" on YouTube. Make sure to add "engines" to the end or you will be watching Videos of Brian Cox the Physicists until the sun fizzles out.
Good luck .
Steve.

 

[Billitmotors]

G'day Werowance
I found your story again.
Firstly, don't let someone else have the pleasure of starting your new engine for the first time, I would encourage you to persevere.
From the sound of things there could be a number of things going against you.
I would suspect that the fuel you are using isn't up to scratch if you are not even getting a pop out of your engine when flicking the prop.
The fuel mixture that I use is 20% caster Oil, 30% Ether, 50% Kerosene. Although the last time I bought kerosene from the local hardware it was poor quality and it was suggested to me that the suppliers had added something to it which retarded firing of the engine.
I would suggest that you try to find one of your local model flying clubs usually one of the other members can get Ether and they are usually happy to sell you some for a good cause like running a home built engine.
If you have made the venturi to the drawing sizes you do not need to restrict the air intake the engine will run fine as it is drawn.
As I remember it you said that you shaved off the top of the crankcase where the cylinder mounts to the crankcase have you made a packing piece to repair this because by doing this you will have changed the timing.
Also try and poor some fuel around the cylinder crankcase joint and then turn the prop over and see if there is any leakage around this joint. If there is you are loosing crankcase compression and the fuel air mixture won't be transferring to the cylinder properly even so you should still be getting a small bit of firing when you flick it over.
Try and put a very small squirt of fuel inside the exhaust port and then flick it over it should fire after the second or third flick if your contra piston is somewhere close to it's running position.
It could also be the fit of your piston, liner, contra piston. Invert the engine, and again put a small squirt of fuel into the exhaust and turn the prop to close off the port and continue to turn the prop gently, all the time looking in the exhaust port to see if there is any blow bye past the piston.
If all your fits are good there should be no leaks and provided the contra piston isn't backed off to far the propeller should come to a hydraulic lock, don't force it past this position. Also if it hasn't leaked so far remove the compression screw completely put your finger over the compression screw hole and flick the prop over. If you feel any pressure change from the hole then your contra piston is leaking.
When trying to start the engine, install an 8"X4"prop, set your tank up so that the centre line of the fuel feed pipe is in line with the centre line of your needle valve, make sure that your compression is backed off. Try to start with no fuel in the engine, open the needle valve about 3 to 4 turns. put your finger over the venturi and turn the prop over 2 times making sure that the fuel was already drawn up to the needle valve. At this point remove your finger from the venturi and give the prop a good flick. If it fires you are getting close to the running position. If not increase the compression by about an eighth of a turn and flick the prop again continuing until the engine fires, about every third try you will need to put your finger over the venturi and draw a little more fuel into the crankcase.
Once the engine fires increase the compression a little more and the engine should run.
at this point you will probably need to increase the compression slightly more and the engine should run steadily at this point you can wind the needle valve in and your engine should increase the rev's.
At this point don't run your engine to hard at first as everything will be bedding in and there will probably be a few tight spots, just let it run and settle down. Let it run for about 2 to 3 minutes at a time slowly increasing it's speed as well as slowing it down until it has had about 20 minutes running.
Remember if you force it and something breaks all spares will need to be remade by you.
I hope this helps please let me know how you go.
Rob Jenkins.

 

[werowance]

Thank you Rob Ill give it another go. honestly I never got back to remaking the connecting rod from the other night. to much honey do work... and its my anniversary this weekend so probably wont get to this weekend. but the rod is a quick part to make and I think I still have stock the right thickness left over (fingers crossed)

on the fuel, its store bought aero Diesel fuel from tower hobbies specifically for diesel engines, I had also tried the homemade mix which is pretty much the same as your mixture some time way back. but since I am getting a few kicks now, I may try mixing my own again to see.

on the head and shaving it down etc, that was some time back and I had already gone back to the standard drawing dimensions (remade parts) so we are good there. I'm actually on about the 6th cylinder and pistons remake lol. but the contra piston has that slight taper and is good and tight no fuel blow by on that getting into the head.

on crank case leakage. that just might be one of the issues ill double check on that.

on 8x4 really don't know much about props dimension but the one I am using was a 2 blade 7 inches long prop. but on this last test I used a biger piece of wood that was about 9 inches long and thicker. but I assume 8x4 means 8 inches long and 4 blades? ill ebay for one if so while I'm remaking the rod

 

[Cogsy]

8x4 is an 8 inch prop with a 4 inch pitch - it's still 2 bladed. The higher the pitch number the more force required to spin it, but the longer the prop the more 'flywheel effect' it has.

 

[Billitmotors]

G'day Werowance
from past experience, store bought diesel fuel is often low on the volatile component of the mix, so the home mix fuel is always a better bet, provided you can get the ether. Also only mix enough fuel for running on the day.
On the crankcase leakage also check around the front housing and the crankcase by pouring fuel around the joint and then turning the propeller over and checking for air bubbles.You might need to cut a paper gasket to suit.
As for the propeller size Cogsy is spot on. I only use the 8"x 4" prop to get the run settings and for initial running after the engine is starting consistently then swap to a 2 bladed 7"diameter 6" pitch prop.
I have been running a 7X6 on my Cicada to fly a control line Veron Viper for some time.
I'm currently working on a pair of Naylon Vipers but I haven't had a lot of time in my workshop lately.
Rob Jenkins.

 

[777engman]

Hi there Werowance, just wondering how you goton with the littlediesel? any luck yet with starting it?
cheers
Dean

 

[werowance]

havnt had a chance to do much yet. I started a major shop cleanup and strip cleanup on the lathe/mill combo. just finished that up this weekend and started cutting down a pice of 2024 aluminum to make the new rod.

if I'm lucky ill have a new rod by this weekend.