B.J. Cicada build

[Cogsy]

I'd go for the 5/16 (8mm) personally. The bigger the bar the bigger it's minimum bore size is. My 8mm bar needs at least a 12mm hole to start boring, so I can't bore a hole under 1/2". Having said that, the bigger the bar the deeper you can go, but my little 8mm can do 2" deep without a problem.

 

[werowance]

Got my new boring bar in today and did another test run and I am very happy with the result.

I bought a shares 5/16 bar with the suggested carbide shape and I produced a decent flat bottom hole. Cogsy and Jasonb thanks for the recommendations on the bar and carbide tip/technique using that tip.

Pictures of the new bar as well as my test hole in a cast aluminum ingot. The little dark marks in the hole are not swarf or dust but rather air holes in the ingot casting. The face cut was done quick and dirty just so I could get at the test bore so ignore the horrible face. just needed it to be sort of flat. End result was a great fit with a great flat bottom (bore and bottom not the face). Just hope I can repeat it on the real part. May try a few more test cuts before the real one

Hope to have some more progress soon. And again thanks for the bar recommendations. Much better

 

[werowance]

more progress last night. bored the 7/8 hole and it turned out nice. a nice tight fit with the nose cone part and a nice flat bottom hole.

picture 1 block squared up in the 4 jaw, picture 2 the finished hole i broke the sharp edge with some emory clothe while running in lathe, picture 3 this is me holding the block with the nose cone pointing down to demonstrate the good tight fit and it doesnt fall out. the picture rotation is missleding, it is pointing down toward the floor.

 

[Jasonb]

Looking good

 

[werowance]

while its on my mind, a few more questions.
1, plan to bore the .625 hole for the cylinder in the crank case first, then cut the cylinder to fit. right?
2, on the cylinder, the cooling fin drawings call for a 7deg taper cut. i was originaly planning on just using a parting tool and to straight plunge cuts for the fins but i sort of like the angled look. if i were to try the angled fins, what would you all sugguest for the cutting tool and procedure? ground form tool sort of like a parting tool with 7deg ground on both sides and plung cut? i may just end up doing straight fins but am curious how one would do the angled fins.
3, fuel, i know its a diesel, but i assume it wouldnt run on diesel fuel right? i happen to have some nitro fuel for a glow rc car i have would that be acceptable - i know im thinking way ahead here but thought id be sourcing the chemicals if i have to mix up my own.

thanks

 

[Brian Rupnow]

I like the blue thumbnail!!!

 

[canadianhorsepower]

I like the blue thumbnail!!!

Brian can you explain

I didn't understand what you were referring to
When you mention Blue Finger nails!!!!!!!!!!!!!!!!!!!!!!!


It wasn’t being nasty.......................was it??????????????????:fan:

 

[Jasonb]

I think he was refering to the copious amount of blue used and the unusual method of applying it with your thumb

1. Yes hole then cylinder

2. I would do straight parting cuts first then swing the topslid eround to 7deg and using the same tool take a light cut down the side of each fin to taper it, make sure the cutter is sharp. If you use a form tool there will be so much cutter in contact with metal it will chatter and likely jam solid and there is also the risk of bending teh fins away from the cutter.

3. You need a mix of Kerosene, Oil (usually castor), ether and possibly an ignition improver but not really needed for a display engine. Some suggested mixed diesel part way down this page. Glow fuel won't do.

http://colinusher.info/Model Aircraft/fuel.html

 

[canadianhorsepower]

I think he was refering to the copious amount of blue used and the unusual method of applying it with your thumb

/QUOTE]

Ha ha ha
I should have realise that myself
Thanks

 

[werowance]

I like the blue thumbnail!!!

ha ha, everyone's a comedian..... yep i did get a bit messy with it. was holding it in my hand and it ran over my thumb. i do like a deep blue part as the scribe lines show up much better in my dimly lit shop. gotta invest in some more lights.

Brian, hows the cam cutting coming along?

 

[werowance]

more progress and a slight issue i hope will not affect running.

also note no blue fingernails in the photo's Thm:

first picture, the 5/8 hole bored and dead on measured with my new bore gauge

second picure, finishied bore

third picture close up and notice i wend just a bit to deep with the half inch drill before i switched to boring bar, on the little half moon you will notice a smaller half moon where i went to deep. i dont think this will interfere operation

fourth picture, this is the first hole i cut the 7/8 one, notice where the chuck made an indention at bottom (in the photo its on the right) but the bottom if the engine were setup and running. i used card stock in my chuck jaws but there was just to little material left thus it mared a bit. if i had to do it over, i would bore the 5/8 hoe first then teh 7/8 second. the little mark on the metal doesnt seem to interfere with fit of the nose cone so i hope this wont cause a running issue.

 

[Jasonb]

The small mark from teh 1/2" drill should not affect anything.

A smear of liquid gasget whan you finally assembel the nose piece will make sure no gasses pass teh dented area. Card is really a bit too soft, try a few bits of perspex or aluminium plate.

 

[werowance]

The small mark from teh 1/2" drill should not affect anything.

A smear of liquid gasget whan you finally assembel the nose piece will make sure no gasses pass teh dented area. Card is really a bit too soft, try a few bits of perspex or aluminium plate.

what is perspex?

 

[werowance]

"what is perspex"

never mind, google is my friend......i see its plastic acrylic sheeting.

thanks much.

 

[werowance]

Tiny bit of progress. Wanted to make my own 4/40 screws with some pieces of ss rod I have. But my slitting saw arbor was trashed so needed to make a new one out of some scrap mystery steel

That said the new one I used my new learned boring technique and bored the arbor to hold the end cap of the saw arbor. Just a quick and dirty one but think it will do the job

Next are pics of the first screw which I have already culled as the second one I changed carbide to a sharper point so I could get a better square cut under cap to threaded shaft.

Well.....only 9 more at least left to cut. Might do a couple more cause if I drop one I'll never find it as tiny as they are

Picture of first screw has my finger behind it just to get the camera to focus on the tiny threads. (And for Brian not no blue on fingers. Just grime from a brake job on wife's car lol). Just kidding. Brian hope u are still following as well as the others. It keeps me going and wanting to finish

Any way enjoy the pics

 

[werowance]

Started on the crank last night, going to try a grade 5 bolt instead of the very large track hoe boom pin i was thinking of using. the bolt cuts very easily and was much closer to the size i need so less waste of time and material.

i have been reading several of the different ways folks have done the rod journal pin on different cranks and i think im going for option 3 below but would like to know what others have to say?

1 - use .250 drill rod and silver solder in - saw Brian Runpows experience with it and understand that leaving enough clearance for the solder to flow in can also cause the pin not to be square, but he was working on a more complex crank than i am in my opinion.

2- make an offset jig like in this post http://modelenginenews.org/techniques/crankshafts.html
and cut the journol - have had some experience with offset interupted cuts before and really didnt enjoy the cut nor did i really like the resulted part

3 - use .250 drill rod, loctite and press fit it in sort of like in this thread
http://www.model-engineer.co.uk/forums/postings.asp?th=70308&p=1
the reason i am leaning toward this option is i have the drill rod, and i have the undersized reamer for good tight press fit already. i figure this will be the quickest, easiest, more acurate due to my limitations and will probably come out looking better. its such a small engine i dont think i will have any durabilty issues or problem with the red loctite coming appart and the pin moving out?

id like to hear experiences from others so that when i get to the rod pin end, im a little more prepared make the decesion.

thanks

 

[Cogsy]

If you go option 3, for added security and peace of mind, you can cross drill and pin the joints as well. I've used both loctite and soft solder on the pins (on different crankshafts) and had no problems.

 

[Jasonb]

For some reason I would go with option 3

You can mill away a lot of the waste to make the cutting easier on option two

 

[werowance]

more progress this weekend, and almost a failure. i had posted earlier that i already had the .250 drill rod and undersize reamer to do the crank pin, well after i parted off the crankshaft i went back to the drawings and found i had missread the size and the .250 was actually the outside curve of the rod.:wall::wall: so i took that drill rod and cut it down to the correct size and after 4 attempts of that i finally got it right and to a press fit with lock tight. also note the threads on the crank were left longer than plans, i will cut it to length when i have my prop mounted.

posted below are:
1: photos from the other day that i didnt post of me slotting the ss 4-40 screws i made
2, 3 and 4 are the finished crank

5 and 6 are what i have so far assembled.

 

[werowance]

more questions...... and thank you to all for all the help.

studying the plans further and trying to do things like locate materials and decide on a game plan for each cut and while i had some spare time today at work i have come up with these questions:

http://modelenginenews.org/plans/BJ_Cicada.pdf

on sheet 3, can i get by with cheaper aluminum for the prop driver?

on sheet 3, on the piston, it says .437 "hone" i have seen in one of my magazines where a guy was using a clamp looking hone to work on i believe it was vintage motorcycle push rods. may have been wrist pins, but is this they way the plans are calling for it to be honed? or would you just cut a cast iron rod long enough to get both piston and contra piston out of to diameter, and start working it in and out of the cylinder untill it can go all the way through, then part your 2 pistons out of this rod?
- also what is that type of clamp hone called?

sheet 4, the mounting holes at the bottom of the cylinder, how would be the best way to locate those to the crank case? the crank case has not been drilled yet either because i was trying to decide how to get them all lined up, the only way i can see is that i am going to just have to bite the bullett and do my very best at acurately measuring then marking both then drilling them seperately. i was hoping to figure out a way to drill the cylinder first and transfering some center marks to the crank case but how with the cooling fins sticking out further than the bolt holes?

sheet 5, the carb venturi section. any problem using cheaper aluminum here? and also what about brass? im not concerned about the weight.