soarrich

My Feedback: (98)

I'm building my own .049s. If they put out Baby Bee power I'll be happy. They are all going to be AAC, but one will be piston port induction, one reed valve induction, and one crankshaft port induction. I think they all will use exhaust throttles. This is how much I've completed so far, the TD is for size comparison. I had to cut the picture in half to post it.

soarrich

My Feedback: (98)

Cranks and bearings..The KK needle valves and bearings are going to be the only things I don't make myself.

DICKEYBIRD

Hi Rich,

Great project!! Please keep us posted on your progress. I, for one, would be very interested in more details such as how you achieve the piston/cyl fit, the materials used on the various parts, crankshaft, rod, cylinder liner, etc. Just about anything you care to write would be very interesting.

Thanks!

ps: Next, could you do a 4 stroke 1/2A engine?

Jeff Leavitt

Nice project Rich....

AAC? What kind of wrist pin set up will you use? Will the piston, rod and cylinder interchange with the standard cox stuff? I see what looks like piston blanks in the picture. What alloy will you use? Bar Stock? Thanks for sharing your project, keep the info flowing..... Jeff....

BMatthews

As someone that's looking forward to having enough time to make my own as well I'd be really interested in this project. Keep the news flowing..... OR ELSE

soarrich

My Feedback: (98)

Aluminum piston, Aluminum sleeve, Ceramic coated. The ceramic coating is just hard anodizing.

The wrist pin will be 1/8" drill rod. The con rod will be 6061 t6. Nothing is being made to be interchangeable with Cox. The bore x stroke .40x.39 or as close as I can get, I'm not a machinist, I just play one in the garage.

I plan on lapping the cylinders and pistons with buffing compound to get a real close fit, with the piston and cylinder both made from aluminum the fit should stay as the engine heats up.

ajcoholic

My Feedback: (10)

Just a question - not knowing of your previous engine building experience (if I am out of line let me know) I will offer some help.

When you lap a piston to a cylinder, you do not actually put the piston in the cylinder bore with lapping paste and go at it. If you do, the fit will be WAY too loose and also you will have lapping compound embedded in the piston, cylinder that will be hard to get out.

This is how you lap an engine:

firstly, the cylinder should be bored out about 1 thou undersize. Then an internal lap is made up (its a lot easier to email a photo than to describe) but basically you have an aluminum, brass or cast iron cylinder that is turned to the size of the bore. Onone end you drill and tap to accept a cap head screw that you have turned a taper on the head. Then the lap is spit into 4 segments, so that when you turn in the tapered head cap screw the lap will expand yet stay cylindrical. Now you can charge the lap with honing compound, I prefer the use of diamond paste (micro diamonds in a grease carrier) that is available in different grits. Can let you know where to get it if need be. Now you chuck the lap into your lathe, and place the rough cylinder over it. Tighten the lap up so there is a bit of drag, start revolving the lap (at about 150 to 200 rpm) and use some oil for lube stroke the cylinder back and forth over the lap. Once enough material is removed to lessen up the friction tighten the lap screw a bit more and continue lapping untill ALL machine marks are gone.

IMPORTANT: if you want a taper in the cylinder (and I suggest about 1/2 thou taper from top to bottom) stroke the cylinder more on the lower end.

For the piston, you must make an external lap. I use 1/2" aluminum plate, bore a hole the size of the piston and then slit it and make a screw to allow the lap to be closed down. The piston blank will have to be mounted on a mandrel, and the lap charged and then stroked over the piston - basically the same as the cylinder but opposite WHat you are trying to acheive is about a 2 ten-thousandth clearance. Its is TOO hard to measure accurately. When I am fitting a piston to a cylinder I will start to check the fit by cleaning the piston, seeing how far it will go up the bore, lapping some more, etc untill the piston will go up allmost to the top.

THEN AND ONLY THEN I will take a minute amount of jewelers rouge, and hand work the piston in the cylinder. Then cleasne everything VERY well, and if you have access to an ultrasonic cleaner that is nice.

In an AAC engine (made to homebuilders standards) I would aim for a slightly tapered piston (crown is slightly, maybe 1/4 thou, larger than skirt) and a sslightly tapered cylinder as well. When you hard anodise the piston and/or cylinder they will not dimensionally change so you can do your final fitting before anodising. If you decide to try some nickel plating (can also tell you where to get that) you will have to plate your undersize piston or liner and then relap.

Hope that helps out a bit

Andrew Coholic

BMatthews

I'm going to toss in a little bit here. AJ has it down pat but for one little detail. The lap material needs to be softer than the material BEING lapped. The idea is that the particles will push their way into the lap and create a custom abrasive device.

Since you're already using aluminium for the cylinder you'll need something softer than that to act as a lap. Copper? Lead alloy? Gold? Plastic? I'm not sure at this point But I do know that if you want to keep the abrasive particles from embedding into the cylinder and piston skirts then this is important.

AJ? I know you know your stuff. Any thoughts on this one? Or perhaps you've already got us beat on this one Soarich?

I must admit to being curious as to the proper material for lapping Al.

ajcoholic

My Feedback: (10)

Yes, I was thinking about that one too - generally speaking you use a softer metal to make your laps from. BUT, because I use the diamond paste lapping compund, and when I charge the laps I smere a bit onto the lap surface, then use a hardened steel rod to rub the diamonds into the lap surface and clean off the excess. I think the diamonds will stay put in the lap. BUT you only will know if you try it!

I am into making repro "old time" engines (and so far all my aluminum pistons have had rings) where I am using a cast iron piston and leadloy steel sleeves.

Model engineering is a trial-&-error type hobby...

Andrew

soarrich

My Feedback: (98)

None, but I have and have read and reread every Strictly IC printed. I've seen you engines in SIC, I miss that bi-monthly fix. Have you ever thought about moderating a forum on engine building? I put in a picture of my other engine project at the bottom.

BTW, The anodizing does grow to measurable thickness, my equipment will grow .001" in 30 minutes. In a cylinder that's .002", so the cylinder will be bored then lapped to about .403", then I'll anodized it down to .400".

AndyW

My Feedback: (1)

Rich,

Great project. For what it's worth, I'll add some comments. I've done some electroless plating and anodizing both decorative and hard. Anodizing the older Norvel pistons would grow the diameter a very, very small amount. My mike could barely pick up the difference but in a tight cylinder, the anodized piston wouldn't go up as far as before anodizing.

HOWEVER, at one point I decided to make my own pistons from bar stock with the plan to hard anodize them. After turning them down so that they entered the cylinder just so, and then expecting a small diameter increase for that just right fit, I found, to my surprise, that the pistons shrank. I did three and they all did the same thing. The problem is that I don't know what grade of aluminum I had. Just some nice bits left over from years ago.

This surprised me because all that I had read about anodizing always spoke of the anodize as growing and making the surface "larger" than before.

I've been meaning to get several grades of bar stock and anodize them to see how each reacts but my roundtoits keep getting back-ordered. What alloy are you using?

Also, Taig or Sherline?

Did you get your anodizing kit/instructions from Caswell?

[email protected]

ajcoholic

My Feedback: (10)

I am not sure how you can "grow" thickness when anodiseing, since unlike plating it is just changing the chemical make-up of the aluminum on the immediate surface and the actual anodise layer isless than a thousandth of an inch?
Andy, I have read a lot on anodising too and all I have read says the opposite - that a finish machined part will not change dims after anodising. You are NOT adding anything to the material, just basically forcing the surface to oxidise.

One other thing you guys have to remember, is that when you are fitting aluminum parts in general, and measure right after they are warm (or hot) on the lathe or after another machining operation you will get a false result. The aluminum will expand with heat obviously, and you should wait (or cool it) before fitting/measuring.

Andy, when you made your pistons did you leave a turned finish or lap them? I cant imagine leaving a non-lapped finish as just turning the piston in the lathe is not good enough.

The fact you have SIC mags is awesome. There is a wealth of info in there not to be found anywhere else. Those are like the bible to me!

Regards,
Andrew Coholic

soarrich

My Feedback: (98)

Andy

I have a Shop-Task lathe, they used to be the importer for Smithy until Smithy decided to go directly to China to get their lathes.

Yes, I got the kit from Caswell for a little over $200, there's nothing you special, it just save a lot of running around looking for stuff and you know it's all compatible. They also give you a nice book on anodizing and plating.

I just ordered more 6061 and some 2024.

I'm going to anodize just the cylinders. I would think you would not want both to be anodized, although all aluminum is in effect anodized the second you cut it.

Andrew

Yea, the temp change in the garage drives me crazy, 40* to 65*, and the pieces range up to 120* on a big piece, I never got the same reading twice. I have since started holding the little pieces in my closed hand for a while to warm them to skin temp, ~80* be for I mike them.

As far as growing, that's what the book says. When iron rust it grows 20x, anodizing is just forced "rusting".

Jeff Leavitt

Great Thread.....

I just got a piece of DELRIN plastic that I'm going to try for laps. When Rich mentioned that his new engine would be AAC, I took that to mean chrome. That led to the next question of how he was doing his sleeves. (if chrome) Most sucessful piston makers on high performance small engines are using a high silicone content alum. alloy. Some are melting pistons from two cycle motorcycles. I've heard that Kawasaki has been the best. I haven't heard of anyone being successful with bar stock pistons. I did a Norvel Rev-Lite this week end for a racing buddy and this engine had the best fit I have ever seen. Annodizing provides far better results than I though it would, and it showed this as well. The AME 0.49 went 32,300 on my test bench and I think it has some more left in it.

My question is, I would like to put a nice finish on chrome cylinders. I have some 1200 diamond lapping paste but am wondering about the best way to polish the cyl. with it.

Thanks for a most interesting thread......

soarrich

My Feedback: (98)

Maybe we need a new dez...AAA Aluminum Aluminum Anodize

From what I understand you can't take high silicone aluminum alloy and just cast stuff from it, the silicone come out of the mix. The best thing I heard of was to cut up pieces of pistons and turn them down into our tiny pistons.

I am using bar stock, others have used it and have been successful. In my case I'm hopeful to get Baby Bee performance, the only way I think I could get 32,300 rpm is if the prop fell off.

AndyW

My Feedback: (1)

This is a great thread. I've read, and so has Rich, that anodizing "grows" your part. Andrew has read that there is no change and I've had the experience where the part shrinks. Is this a great hobby, or what?

Andrew,

Good point about heat growth but I'm aware of the phenomenon. The pistons I did were turned so that they were a just barely drag fit at the top of the tapered cylinder. After anodizing, the pistons fell right through. All components at room temperature. I was hoping for that squeeze fit at the top after the pistons "grew" from anodizing.

OK, we all have to limber up our search engines and do a little research, maybe.

I've got some of the VA MK2s and the pistons look like they have machine marks on the surface. Very, very light, but they're there. When I turn down pistons, for the final cut, I use a specially shaped tool that is basically a broad, half moon shape. After grinding to shape, it's polished on a diamond stone so that the cutting surface is very smooth. It gives me a finish on the piston surface that is better than the VA and more like the Norvel AAN pistons.

Anodizing leaves a hollow, honeycomb matrix. A microphoto of the surface even looks like the material is "grown".


I've been given some old, dirt bike pistons and I've been meaning to cut them up to make up some Norvel pistons. Maybe this will be the impetus to do that. However, they don't appear to be high silicon as far as I can tell. There would be no need for high silicon as these use rings and don't ride directly on the cylinder's surface to affect compression seal.

Rich,

Yes, AAA sounds good.

I too have read, or heard, that melting down high silicon aluminum may not work. However, for our purposes, maybe the loss of silicon isn't enough to matter too much.

Metallurgy isn't my forte but I've made some observations. The original, VA MK1 had pistons made of high silicon aluminum as told to me by the importer, Dan Rutherford. The surface has many, grey pits in it, as if the aluminum were a sintered material. This, apparently, is the silicon showing through. My assumption. Then VA pistons changed their look and lost that grey, pitted look and looked smooth and shiny just like any old bar stock. What alloy it was, Dan was never told. These pistons worked just as well as the originals. Norvel started out with pistons of the same ilk. HOWEVER, the Wasp .061, which is a clone of the Norvel AAN engine, uses a true, high silicon piston. So do the other Wasp engines. The Norvel pistons turn down easily on the lathe using high speed bits. The Wasp pistons dull your high speed bit real fast. I had to use carbide bits. So, if a material doesn't have the grey, pitted look, it's not really high silicon aluminum. It's something else and try as I might, I can't find someone who knows for sure what it is.

What's your strategy for hard anodize compared to decorative anodize? I understand that your acid bath needs to be weaker, you use more volts and amps and the bath must be cold, at just above freezing.

Jeff Leavitt

Andy,

Regarding your observation about the motorcycle pistons being ringed. It's my understanding that rings vs. no rings isn't the issue. Air cooled, high performance engines have dimensional stability challenges and that's the reason for the hi silicon content. I'm not a metalurgist either so more research is definately in order... It's amazing how well these anodized parts can hold a seal. And, a tight fit dosen't always guarantee a good seal... Jeff

DICKEYBIRD

Hi guys, coincidentally I ran across a thread on RCWatch http://www.flightlines.com/forum/index.htm (go to the controline forum, 17th down from top & click on "Lapping 101") where some of the old masters get into a mild pi$$ing contest about lapping. Some very good input given that I'm sure you masters over here are familiar with but I thought it was a good read.

AndyW

My Feedback: (1)

Jeff,

Yes, dimensional stability is the issue. But, again, I've observed a number of different pistons that all supposedly had high silicon content. Those that showed the grey "mottling" were very hard while the "shiny" ones were relatively soft. I'm just curious as to the difference in hardness and appearance. In any case, either alloy works well in AAN and ABC set ups.

I agree that anodizing, even with a, not so tight fit, can help compression seal a lot. I've had a number of baffed AAN Norvels that were revived just by anodizing the pistons. It appears that the honeycomb surface absorbs and holds oil for a good seal.

If anyone has baffed AAN Norvels they want revived, just get ahold of me. Its worked for me but I'd like to do a few for others just to get confirmation.

Also, you say you "did" a Norvel Revlite for someone. I have a number of Revlites and before I adopted the heat gun to break in routine, a few have become "baffed". That is, the squeeze at the top is gone. Yet, if I use an electric starter, they fire right up and I still get quite good top end compared to when new. What was it that you do for people to get those kinds of numbers?

Milton,

Many thanks for the link on lapping. The really nice thing about RC Universe is the lack of pi$$ng matches. Just respectful exchange of information and ideas.

To all for comment,

Something puzzles me about Cox and Norvel. I've read for years that Coxs run too cool and that accounts for some of their problems as an RC motor. This was explained as the dynamics of such a small motor, in that there's a relatively large surface area compared to the displacement. Yet, all the new Norvel Revlites (and even some of the old AAN engines) have massive cooling fins compared to Cox. The Revlites follow conventional AAN and ABC practice in that a tapered cylinder is used with a tight fit when cold that, with heat expansion, becomes just right at running temps. However, if you run such an engine rich, this cool running won't allow the cylinder to expand enough and you risk losing your fit due to excessive wear. The Revlite's massive cooling area seems to contradict conventional practice yet with care, works just fine. Theoretically, these should wear out sooner than otherwise just from running too cool. To test this, I've turned down the fins on a couple of .074s and an .061. Will fly these next summer and see how long they last. These have had their heads gold anodized and look right pretty. Nearly as nice as a Cox engine.

ajcoholic

My Feedback: (10)

Regarding anodising:

Some sources use the term "grows" when talking about the oxidiseing layer. but, I think that is misleading, as the layer is thin, no where near 2 thous or even one thousandth. You are not adding or removeing material, just changing it on a microspcopic level. It is common pratice (to my knowledge gained) that parts destined for anodising are finish machined to exact tolerances and then anodised - becuase they stay the same dimensions. I guess I will have to machine something and try it to see if any measureable change is taking place - but I dont think so.

For lapping chrome - diamond is the ONLY way to go. Will work very very good.

Andy - in regards to machine marks... why not make a simple aluminum lap like those I sent you photos of a few years back? Machine marks on a lapped engine are a no-no! The BEST made engines have pistons that glisten like a polished mirror. No marks.

And more importantly, it is not so much the machine marks but the fact that a lathe turned piston (and one done on a lightweight hand fed lathe like a taig) will NEVER be perfect. Argue that if you may but any small vibrations that are set up while turning will allow some small out of roundness to occur, or even microscopic "flats" to occur as instead of a truely round piston (or conversley , cylinder) you will get a polygon shape. Thats where lapping will turn that into a PERFECT circle. Its the nature of lapping to allways produce a perfectly round object. Its so easy not to do it is a shame!

Again, we are talking working to a ten thousandth tolerance - hardly obtainable with a hobby lathe. But TOTALLY obtainable with a simple lap! Wonderfull stuff!

I am no expert by the way. There are lots of things I want to try and hope to build and try some day. My damn job keeps me too busy - and there are not enough free weekends and evenings in the year to satisfy my hunger to try new things in the machining dept. But, I can say I have built dozens of IC engines over the past 5 or 6 years and have gained some experience. I am part of a model building group that did include George Aldrich before he passed away and had the pleasure of speaking to him regularly regarding engine construction. That man could tell you a thing or two about lapping and fitting a piston/cylinder! But I digress...

To me, the most important issue is to try new things, make mistakes and learn from them, try new things, make more mistakes, eventually get something to work.... try MORE new things! Its a wonderfull aspect to this hobby and I am glad to see more guys into it.

Andrew

Jeff Leavitt

Dickiebird,

Hey, thanks for the link to the lapping thread. Very interesting read.

I noticed the name of Wayne Trivin and his comments. If your not famillar with Wayne, go to the lapping thread and see his posts near the bottom. He's included a link to his site. I guarantee you, if you like 1/2a engines you'll love his site. He's a very accomplished fellow, built some way cool stuff.

I think AJ said it. One of the neat things about this hobby is your free to try out your idea's. Every once in a while you'll win one, with great personal satisfaction. The other thing is it's incredible how much time you can get into 1/2a engines, these little suckers can eat a whole evening in the blink of an eye!

Andy, I'm trying to come up with a digital camera to document the steps taken and performance of the AME engines. The finishes I get on the parts, ie, crank and piston are georgous and could be readily seen via a good picture. I ream the crank bore and do a blueprint job on the engine using the "The Engine Analysis Program. If I can get some good weather I'll shoot a picture of my digital tach with the engine running...Somebody said a picture is worth a thousand words... I'll not argue.... Jeff

AndyW

My Feedback: (1)

Jeff,

You and Andrew have got it exactly right about trying out ideas. For years we were told that 1/2As can't be made to throttle well because of sub-piston induction. Despite that wisdom, I tried a throttle on the VA MK1 (which has SPI) and discovered the best throttling engine I've ever had in 30 years of modeling. Likewise my modified Norvels which also have plenty of SPI.

After noting that the pistons on the VA MK2s seemed to have machining marks, I concluded that this is all you needed to do to make pistons. This didn't work for the reasons you give. While I got a smooth finish, even after anodizing the piston, I got poor compression seal and low power. I finally concluded that the pistons were not really round within the tolerances required. So, no argument from me on that score. Just describing what I did and why.

One of the reasons I didn't try lapping was not having a source of lapping compound. I didn't want to spend the money for a proper lapping set up just for the sake of one experiment. Now that I have some interesting perspectives on the subject, I may reconsider. Might even try Comet cleanser or toothpaste, as one wag suggested along with the great idea of a delrin lap.

A search on finishing.com reveals that growth is a factor when anodizing. Not much, granted, but perhaps enough to be a consideration when trying to get that just right fit. Additional reading leads me to believe that maybe I just didn't let the parts anodize long enough.

None of us are experts 'specially ME but I'd bet if we were, we wouldn't be having so much fun trying new stuff. Gotta keep trying new stuff, gotta keep it fresh.

Rich. Bet ya had no idea what you might have started. All of us, I'm sure, are glad you did. Hope we haven't discouraged you with too many opinions. Please keep us posted on your progress. I note that you're going to try three different induction porting systems. This leads me to believe that you're curious as to how each differ in performance. That makes your project doubly interesting and important.

soarrich

My Feedback: (98)

If I had seen Wayne Trivin's web page first I may have just sold my lathe on eBay. I am surprised at the response, I had no idea the amount of interest in the engines themselves, I kind of thought I might get "Take this engine stuff someplace else" response.

I'm doing the three to see the problems and advantages with each. My quality is so bad that I don't think I can draw any conclusion as to which is the best type, though I think the reed valve will be the most powerful of the bunch.

DICKEYBIRD

I can only offer a teeny little hint to the lapping discussion. When I'm trying to tame a particularly stubborn Cox piston/cyl. (I mix & match parts to get a snug fit and some of 'em are too snug) I lap with the German chrome polish, Simi-Chrome. I have a short piece of brass tubing that I gently press onto the ball socket boss to grip the piston tightly and spin the piston in the cyl. with a low voltage cordless drill. The final finish looks like chrome it's so slick! This is of course after miking a box of used pistons and picking those that are REAL close to being round. That DOES make a difference! I guess what I'm doing isn't lapping in the true sense of the word, just polishing.

Jeff Leavitt

Guy's

I've made my own lapping compound from a mix of Jewelers Rouge and oil. It's a mild cutter so you don't get yourself in trouble. The other compound I've used is a mixture of Bon Ami cleanser and oil. Doug Galbraith did a nice article on improving performance on the CS engine. This article is a good read as it has some good info on making laps and many blueprinting tips. I'll see if I can find a link to it and post it here.

Andy,
This Delrin thing will really work good if the abrasives will imbed in the Delrin. If that works, the easy machining qualities of the Delrin will make it easy to make a high quality lap. I'll keep you posted. The fit and seal of these engines is the most important factor for hi performance. Compression is no. one power factor. All this lapping, sizing and polishing is well worth the effort.
Rich,
Keep the lathe! you'll be lost without it... Remember there are very few Wayne Trivin's around and, they started just like us. Who knows, your new EDM Machine could be just around the corner!........Rgds,.....Jeff