Nice work Captain. That's exactly what I had in mind to use... If I use my left hand thread crank, I will either make a setup like you are doing, or cut off the left hand thread and bore it for a stud.

AV8TOR

Capt: A) Will the bolt-on part have the LH threads?; B) Will you retain the key and keyway? ; C) Will the the final product have the bolt heads on the back of the flywheel center? Just having trouble visualizing rotational alignment of 'drilled nut' and fixed relative position of the threaded holes in the 'back plate / flywheel center' Looking forward to explanation of just how to accomplish this procedure. Good Luck.

Do you have verical clearance on your drill press to drill the holes with the hub tight on the crank?

I question the ability to easily repeat proper alignment and tightness of the 'nut' portion. Some of you machinist, please clarify.

captjohn,

Very nice work on your hub. I already have the hub and prop washer/nut from Roy Sholl for my eng. set up for glow/gas. All I need for the other eng. is the prop adapter, washer to butt up aginst the flywheel, with the L/H threads that I can run as a stright ignition. No taper required. Any way you are doing some good R&D work there plus getting some good practice using your new equipment. Keep up the good work. I see you are still in the deep freeze up there. We are still in the 30 to 40 range here.

Later George

mikenlapaz: The prop hub itself will NOT have internal threads to engage crank threads, but a hole bored for clearance. To keep both parts on center a ..030 deep hole will be bored in the flywheel center to keep the extended part on center. The extended part will be a sung fit in that hole. The three bolts will come from back side and thread into the extended part. Then it will be possible to machine the extended part to what ever length you want and knurl it. Then drill and tap for right hand threads. Before I can do this I need to get some larger dia aluminum stock. Yes the key will be in what is left of flywheel. That with locltite on taper and left hand nut will work good I believe. The idea of all this is to be able to machine the assembly like its all one piece. The three bolts can go all the way through and have pal nuts on them if you want. That is a option. Another option is do not cut as much of a "neck" in the extended part and use longer bolts from backside. Now I hope it works!! Capt,n

So, you're going to have approximately .630 in. open space between the back of your hub and the front of the engine??? What you are doing should work fine on the test stand where the only loads that your turned flywheel center section will see are torque loads. OK, for the loads on your center section you have to add the front section of your prop hub (moment arm), then you need to consider the gyroscopic loads (bending) of a 16 or 17 inch prop plus the moment arm. You are going to be putting a lot of stress on a very small area of CAST ALUMINUM that was designed for torque loads only when you are actually flying this setup. Just my opinion, others may disagree. Good luck with it.

flipflop...you have a good point. There is a lot of engines with far more power than this one and that same center piece is holding a complete flywheel and extension with bolt. prop washer and prop and I have not heard of any coming loose yet. No one is going to be in front of or in line of any prop set-up of mine, or one I buy. If it explodes in air...so be it. I have seen a engine come off a airplane and the guy still did not crash his plane. Thanks for you input...even better would be posting more photos of each step on how you think it should be done. Capt,n

I would like to finnish up and try this set-up if I could find a Left-hand tap that did not oversize the threads like the 2 taps I did get. Flipflop...just how tight was the left-hand threads you did? Thanks Capt,n P.S. This adapter could be shorter by over 1/4 inch and still have plenty of threads past crank nut.

[quote]ORIGINAL: mikenlapaz


Capt: A) Will the bolt-on part have the LH threads?; B) Will you retain the key and keyway? ; C) Will the the final product have the bolt heads on the back of the flywheel center? Just having trouble visualizing rotational alignment of 'drilled nut' and fixed relative position of the threaded holes in the 'back plate / flywheel center' Looking forward to explanation of just how to accomplish this procedure. Good Luck.

The key is soft metal and will shear and has no use in our application. The sole purpose of it is in final assembly in the factory to install the flywheel at the correct otientation for timing. I still don't trust the LH threads. Maybe on this size engine but I wouldn't do it on anything bigger for sure Loctite or not it scares me.

Tim220225: I see what you mean about the soft keyway. What do you think of making a steel duplicate of flywheel center out of steel and use a steel key-way? Should be a lot stronger for sure. Capt,n

You might want to get a better bolt than that one in the picture....Grade 8 is way stronger and not that expansive....

RCIGN1: I was thinking about using a allen head bolt. I will make sure that is Grade 8. If it was your engine...how would you go about this Left hand thread deal? Thanks Capt,n

Wasn't addressed to me, but I still think the ideal fix is to bore a pilot hole in the crank, then cut off the left hand threads, then bore and tap the crank for a right hand thread grade 8 stud. It's a lot less work than the two piece prop hub as well...

AV8TOR

av8tor1977: What about the taper on the crank? Explain your complete process. Thanks Capt,n

Av8tor's method will work fine.....I converted a few 3W 106s this way, but it takes a really good drill and tap, the crank material is pretty hard...If you do it that way cut the threads off first, then use a small center drill on the end of the crank..Use a good cobalt drill, maybe a #21, to drill a pilot hole, then use the correct drill size for the tap..Makes it easier...
Go slow, it's hard material and going too fast will just burn up the drill and work harden the crank, making it even harder...I usually lock the chuck and put the tap in a drill chuck in the tailstock and turn it by hand into the crank...
The cheaper bolts work OK on small engines, but if you tap the bolt for a 10-32 spinner bolt the head can break off a grade 5..Been there, the spinner went about 100 yards across El Mirage dry lake when the head came off...
Most hardware stores have grade 8 hex bolts, a 5/16 is less than a buck....

RCIGN1: Sounds good to me. Where is a good place to buy cobalt drills? Is a place called Drill Bit City 1-800-950-3938 a good place to buy drills? Thanks Capt,n OH ..What about tap magic fluid?

The end of the crank with the threads has a machine centering hole in it. I was thinking of using that to center the pilot hole drilling operation. Then cut off the threaded portion, and then drill the hole to final size for tapping. Eliminates the need for a center drill. But if you have center drills Captain, you can do it that way as well.

AV8TOR

av8tor: I know there is a center in the end of crank already. If you use that center you will have drill .625 or 5/8 of a inch further. The further you drill the more chance of getting off center. May be best to cut off threads grind flat and use a new precision center drill which I have 2 of. Maybe a #21 pilot drill like RCIGN1 recomended. I do not know if fine threads would be best or coarse threads? You never did say what you are going to do about the taper? Capt,n

captnjohn:
www.mcmaster.com/ for left hand jamb nuts and drill the second one on crank and the crank for safety wire. This is for IF and only IF you do the 2 part hub.




Is there a minimum diameter where if become unsafe to use safety wire? I would think that if the hub did loosen it would be apparent before it became a safety issue, maybe not. Opinions?

Gee how about canning the crank and having a spare flywheel? NIB Echo Trimmer or Blower Short Block No Reserve!! 8 shipping and currently under 25 bid.

MIKE-O-CUT No. 87 If you can find it and if you do post source, please.

MIKE-O-CUT No. 87 is down the page a ways


http://www.ashburnchemical.com/Front...s.php?rootID=1

Well I would just leave the taper, and handle it in the ways we always do. Either use the center out of a flywheel and a magneto type prop hub, or buy/make a prop hub for use on the taper.

AV8TOR

A retail outlet is what I was looking for. It was hard to find in small containers on West Coast even 10 years ago.

As per their site; An extreme duty tapping and drilling fluid. Considered environmentally safe. It is thick like honey and sticks to the tap throughout the operation. It is ideal for tapping and drilling stainless steel, carbon steel, inconel, monel, hastalloy, titanium, aluminum and other alloys and exotics.


Working stainless it is super. You don't work harden the material as it does a good cooling job, as well, even when working with hand held drills.

Capt,n Flipflop is referring to the area between the back of your machined flywheel and the seal in the front of your engine. Basically all the forces or loads are on the threaded portion of the crank. Not too stable and can break off. Ideally the hubs should fit closely over the area behind the threads on the crank and be an 1/8th inch in front of the seal as in this picture. This is a 16cc Echo I did some time ago. You don't need the key. Just use a good Loctite type sealer. I use 620 and it is tough stuff. The taper on the crank and hub will lock together even without Loctite.

tim220225: That is a very good looking job you did on that engine. Also a very good job on explaining about the possible breakage. Do you plan on the same set-up even if you cut and re-tap crankshaft for right hand threads? I am wanting to get to another project. I will put the Echo on shelf for now. I have 2 of them and will take one to the next swap meet. I want to trade Echo 2400T off and get a big Moki or something simular. I plan to make a gas head and see how that works. There is a place that will install needle bearings in rod. May even try Gas/glow in one. Just want to try something else right now. Capt,n

These people are listed as being retailers of MIKE-O-CUT No. 87. They are in Houston

http://www.eagle-tool.com/Page384.htm

Here's their catalog in PDF

http://www.eagle-tool.com/EagleCatal...%2028%2006.pdf

Here's another place that lists the Mike-O-Cut No. 87

http://www.clymertool.com/catalogue/index.html