B.J. Cicada build

[Jasonb]

1. Prop driver can be any aluminium you have

2.You don't really need an external hone. You can bore a suitable hole in a piece of brass or aluminium, slit one sid eso it can be closed up and use that with some lapping powder to refine the finish on the piston. A similar process is done with an internal lap on the cylinder liner and the final operation with a very fine 1000g powder is to lap the piston into the liner. I'll find a link to Ramon's thread which shows it.

http://www.homemodelenginemachinist.com/showthread.php?t=17674&highlight=etas&page=16

3. you can make up a simple template like a washer with a 5/8" central hole and the other 4 around it. slip it over the spigot on th ebottom of the cylinder and spot through the positions. Slip a stub of 5/8" bar into the hole in the crankcase to locate the template and again spot the hole positions.

4. Any aluminium is fine and brass should not cause a problem

 

[rklopp]

I suggest you visit Ron Chernich's Model Engine News site for its teachings on cylinder lapping. Forget honing. I don't bother making a split lap for my "Diesel" pistons, however, opting instead to simply finish them long with incrementally finer SiC paper backed by a metal rule, then facing to length. I have done this successfully on 11 engines. It helps that my lathe cuts extremely straight and predictably with respect of diameter, and that I have collets to hold the sized piston for facing without marking it up. (It's a big heavy toolroom lathe with a DRO reading at 0.0001" on the diameter.)

 

[werowance]

2.You don't really need an external hone. You can bore a suitable hole in a piece of brass or aluminium, slit one sid eso it can be closed up and use that with some lapping powder to refine the finish on the piston. A similar process is done with an internal lap on the cylinder liner and the final operation with a very fine 1000g powder is to lap the piston into the liner. I'll find a link to Ramon's thread which shows it.

http://www.homemodelenginemachinist.com/showthread.php?t=17674&highlight=etas&page=16

3. you can make up a simple template like a washer with a 5/8" central hole and the other 4 around it. slip it over the spigot on th ebottom of the cylinder and spot through the positions. Slip a stub of 5/8" bar into the hole in the crankcase to locate the template and again spot the hole positions.

2. thank you ill check that out.
3. using a washer, genious pure genious. i like that idea very well. thank you so much for that one.

 

[werowance]

I suggest you visit Ron Chernich's Model Engine News site for its teachings on cylinder lapping. Forget honing. I don't bother making a split lap for my "Diesel" pistons, however, opting instead to simply finish them long with incrementally finer SiC paper backed by a metal rule, then facing to length. I have done this successfully on 11 engines. It helps that my lathe cuts extremely straight and predictably with respect of diameter, and that I have collets to hold the sized piston for facing without marking it up. (It's a big heavy toolroom lathe with a DRO reading at 0.0001" on the diameter.)

so you are sanding them to size? start a little over size and sand them down with a flat object like using a lapping plate with the lathe spinning it?. ill have to look up SiC paper thats a new one to me. is it like emory cloth or more like wet and dry sand paper?

 

[rklopp]

Yes, I start about 0.0003-0.0007" oversize and polish to size with silicon carbide (SiC) wet-dry paper strips lubricated with oil and backed by a beater flexible steel rule. The part is spinning in the lathe at ~1000 RPM when I do this. I polish with 320, 400, 600, and 1200 grit. To get the size at which to start polishing, I use plug gauges (can be home made) to check the cylinder, mic the one that is about right, then turn the piston to the estimated proper size based on the micrometer measurement of the plug gauge +0.0003 to +0.0007". I clean the piston scrupulously before testing the cylinder fit. I bring the cylinder to the work, rather than the other way around. I sometimes mess up and go undersize on the pistons, but they're small and quick enough to make, it's no big deal. I polish with the pistons 1/8" to 3/16" long so the unavoidable rounded ends get cut off.

 

[werowance]

got just a little while in the shop yesterday and managed to get the collet and taper D-bit made to cut the matching taper in the prop spinner.

started by using my angle blocks and set my compound to 6 deg to the face of my chuck, then took some brass rod and faced/ center drilled it to size then cut the outside of the collet to .300 then using my compound i cut the taper on the outside of the collet.

for cutting the slot in the collet i kept looking for a way to cut that .016 slit in it, finally i came up with a slotting saw that was dead on .016 and decided to try it in my tool holder and it worked great!. i set the tool height with the blade in it to center of my tail stock point then swung it arround and pulling the teeth from left to right for each cut i made a reall nice clean slot for me. cant believe that worked so easily. the idea came from watching manual key way broaching using the cross slide.

next while the compound was still set at 6 degrees i made the D bit. actually i made 2 as i dropped the first one after heat treating it and it broke. i think 2 things are at fault on that - asside from me being clumsy and dropping it. 1. its O-1 and i used watter to quench it and 2 i didnt temper it after that so it was really brittle. on the second one i quenched in oil and then off to the toaster oven at 400 for 45 mins.
i do not yet own any V blocks so i used one of my tool holders from my quick change tool post and sinched it down. then to my height gage to mark the center line on both sides. while still in the tool holder i put it in my qctp and adjusted height and started milling it using my lathe chuck with an end mill in it and cut it to the center line. test cuts in scrap made a smothe clean tapered hole for me. i am happy.

pictures:
1. brass in chuck almost finished with taper cut
2. slitting saw to make the slit in collet
3. finished collet
4. finished collet
5. start of d-bit to make internal taper on prop spinner
6. scribing center line using qctp holder as improv vblock
7. milling the dbit
8. finished d bit after heating.

 

[werowance]

now thinking about the prop driver and the knurles on it. since i dont own a straigt cut knurl, i was considering taking a piece of square stock, milling a grove in it and cross drilling it to hold a single knurle in it. then taking a torch and heating it in the middle and twisting it to a close match to the angle of the knurl, sort of like how a black smith twists ornamental rods for things like iron fence or handles in iron. has anyone ever done this? im wondering if having the knurl rotating at an angle will cause to much stress as it sort of would be pushing sideways of the rotating axis and sort of down on the rotating axis if that makes sense.

also i have seen some swirl pattern prop drivers done but not how they did it. is it likely that was done using a rotary table or something and milled instead of knurling? or is their a technique using a knurl to do that? just curious.

 

[Jasonb]

You can do it using one of the wheels on a diamond knurling tool. I was able to mount the tool very high in the tool post but you may have to take a wheel out of yours and make a simple holder.

 

[werowance]

Thanks, and that looks like the swirl patern i was thinking of. what engine is that prop driver and collet for?

how did you hold the driver after knurling it to ream the rear?

 

[Jasonb]

Its for a Nemett Oscelot/Bobcat/Jaguar

The taper was bored at the same setting (small to large)then parted off so only needed a light skim to clean up the face no reaming required

 

[werowance]

got a few more hours in the garage this weekend and got the prop driver, washer and nut finished, then started squaring up some stock for the rod but didnt get that finished.

faced, center drilled and cut to size some scrap aluminum rod, then cut the angle on the face for the prop washer then parted it off. with the same stock in the chuck i faced it again, Thanks to Jasonb i managed to get that swirl pattern in the knurl on the prop driver. it did take a few tries with re-facing the stock before i got something i liked by adjusting the knurl height, but it worked well once i found the sweet spot. Thanks Jasonb for that info. once finished, i parted the driver off, turned it around and used the d bit reamer and reamed the taper in it. that worked well for me to. then last some scrap hex bar i drilled and tapped 10-32 then parted off for the nut

pictures:
1. stock ready to part washer off
2. finished parted washer
3. prop driver ready to part off
4. finished prop driver, washer and nut
5. loose test fit of it all

 

[werowance]

rod finished and some pictures.

1. blank layed out with marks
2. in vice with drill and rod to hold it square
3. sides milled
4. finsihed rod after rounding in the mill. didnt take any picutres of doing that.

 

[werowance]

now for the cylinder, i have really been dreading this part and have questions.

on sheet 4 of the drawings http://modelenginenews.org/plans/BJ_Cicada.pdf

it shows a .250 offset cut inside the cylinder going .750 deep. am i going to have to mount this in the mill and use a .250 end mill to cut this after i bore the main hole? or should i offset the stock before i bore it, bore the .250 first then move it back and bore the main cyinder hole second?

i might get done by sumer time.....

 

[Jasonb]

I would be inclined to bore the main hole and then cut the other as you say by plunging with a milling cutter. The interupted cut doing it the other way round may affect the main bore.

Other bits are looking good

 

[werowance]

I would be inclined to bore the main hole and then cut the other as you say by plunging with a milling cutter. The interupted cut doing it the other way round may affect the main bore.

Other bits are looking good

so use a .250 end mill and when you say plunging do you mean use the tip and cut downward to vertical depth like a drill bit or cut with the side untill i hit horizontal depth? not sure there would be a speed or finish difference with either way but this is one part i feel is critical to get a good square finish on and dont know which way to cut with the end mill

thanks again for your help. i couldnt have gotten this far without you and the others help.

 

[Jasonb]

Yes use the end of the cutter and plunge it down like a drill. I would do a littel, move the work over 0.005" take another cut etc until you reach the 0.142" offset.

J

 

[werowance]

got a large portion of the cylinder done over the last few days, but looking at the drawings http://modelenginenews.org/plans/BJ_Cicada.pdf sheet 4 and looking at the .750 tall cut witht he .250 bit as mentioned above and i thought that the intake or exahst hole would drill into that little slot. but the plans dont show that. so what is that slot for? why would it need to bypass into the crank case? just trying to understand the mechanics of how this one works.

 

[werowance]

i think i understand it now, when the bottom of the piston passes the intake port it sucks fuel in beneath the piston. then on down stroke the fuel is pushed through the crank case and up the .250 slot in the side of the cylendar to the top of the piston where it is then compressed and ignighted. right?

reallly only used to working on reed valve 2 strokes, so if this is how this one works, thats pretty cool.

 

[hussien95]

Hello all
Very nice work,thank you.
Some time ago and I want to ask about this type
Is this type of engine only works on diesel or are there other additions ????

 

[werowance]

Hessien95, thanks for the compliment.

are you asking if this engine will only run with diesel fuel? or if the engine only works on the dieslel priciple of compressing the fuel until it ignites?

i am told this engine should be run on kerosein and castor oil, id say this engine could probably be made to be glow plug ran by removing the contra pistion, adjusting the height of the regular piston and adding a glow plug. i dont know for sure though.