Japanman

I thought you guys would be interested in these mods for the Fora to make it go.
I spent a lot of hours trying lots of different mods but in the end for the prop at hand (the apc 4.2x2) some pretty basic mods deal out the majority of the rpm increases.

Now these engines came about due to the efforts of Larry Driskill who put up the money to get some prototypes made. At the end of the day things didn`t work out and he is left with a number of engines that he was sent but that weren`t part of the deal.
I am going to ask any of you who are interested in getting a Fora 020, to get it off of Larry as a way of helping coving his costs.

Fora is now trying to get rid of the remainder of the engines. so once Larry has sold out of his stock, you may be able to get them from there.

I thought you guys would be interested in these mods for the Fora to make it go.
I spent a lot of hours trying lots of different mods but in the end for the prop at hand (the apc 4.2x2) I tryed a variety of cylinder porting configuartions and timing changes, as well as crankshaft timing changes, crankcase volume changes etc. But really some pretty basic cylinder and plug mods deal out the majority of the rpm increases.

Remember, the Fora 020 is a big dissapointment in stock form, and it needs cylinder porting to make it run satisfactorally.
When you have successfully ported an 020, you know you could probably give and ant a haircut next!![8D]

Now let me cut to the chase about this engine:

Appart from the stock porting, there are a couple of drawbacks about the engine.
The engine appears to have been made in parts on a CNC lathe, or a Lathe with DROs. Parts such as the cylinder in particular appear to have been made in two steps- first on the CNC and then it seems they have been jigged in a milling machine to cut the exhaust port, drill and tapp screws etc.
It is these second stage operations that are not carried out as well. Luckily these are only the details -e.g the cylinder mount screws can be a bit off centre, or the exhaust port cut slightly off straight! One wonders if a few vodkas wheren`t going down jusyt before this stage of the operation!

appart from these problems, the engines I`ve seen have been pretty good where it counts
The castings are sound and accurate. the crankshafts I`ve seen have been very good and the crankcase to crankshaft fit is very good and consistant.
Now I guess a lot of you guys are wondering about the piston/cylinder fit: it has been very good if a little tight on all of the engines I have seen.

So what do I think? Well, having spent ages on the little suckkers I now rather like them. They are AAC with what looks very much like a 7XXX series aluminium piston. And the engines and cylinders I abused during testing never lost noticable compression.
And with not too much work spin the APC prop at 22K or more, which makes them a usefull little engine.

If you guys have any questions let me know and I look forward to seeing where others take this engine, as I am sure there are gong to be imporvments on what I got.

Stefan

Japanman

Now, before someone makes a smart comment about me not actually saying anything about how to improve the engine...

You can gain 1000 rpms by using a modified cox 020 plug on the stock engine.
If you do more mods on the engine using the 020 plug starts to be even more significant, so I`d recommend doing this to start with.
Also cox 020 plugs may start drying up very soon so I`d get as many as you think you will likely use in the future, I have never had satisfactory runs with the nelson plug.

You will need a lathe. what you do is machine it to be like a norvel head button. The easiest way is by using an old cox 020 cylinder to hold the plug while you machine the fins off down to where the last fin ends, leaving the step where the threads are cut well alone. You want to be careful here: if you take off too much there will not be enough meat left when you machine off the face of the plug.

Machine the shank down so that it can JUST fit into the hole in the nelson head button. I now drill the head button 1mm or so bigger and go a little bigger with the plugs to be safe.

Next you take it out of the cox cylinder and turn it around and hold it in the lathe chuck on the shank as gently as is possible, to avoid damaging the plug seal. Now it needs to be actually clear of the chuck, and you will have to go in with a very thin parting tool to machine the back face of the plug to make it parrellel to the front face.

Machine the front face to raise the compression as far as you dare before you hit the element, now machine the back face of the plug a tiny amount to make it parrellel and you are finnished!

I have yet to blow one of these plugs appart from one that failed when the piston contacted it but then I run 25% nitro fuel max.

S

Japanman

Well, the stars must not be in alignment (no comments please, Mr Pigg) and I can`t upload any images.

Engine mods in general:

Being such a small engine, any engine mods will have and immediate effect. As the engine stands, the cylinder timings, rotary valve timings and venturi size and apparture sizes are all very close to right. don`t be tempted to change any of these prior to running and recording a rpm figure as you will have very likely now changed the balance of timings and diameters wheich are very sensitive on such a small engine, and for example enlarging the venturi alone even by e.g 1.5mm to 1.8mm will make it spit and not draw fuel well.
When looking for a mod to try, see how the engine performs with a couple of different prop sizes to get an idea of where the ports/ timings/ apparture sizes are tuned for and then one at a time suck it and see!!

Cylinder mods:
I got the biggest gains by angling and tapering the transfer passages. In the stock engine you will notice how small the passages are. Further appear to exit TOWARDS the exhaust port, rather than across the top of the piston and towards the boost port opposite the exhaust port.
To get around these problems I used a 3mm coarse diamond bur and after steadying my nerves, re-cut the rear portion of the passages at 22.5degrees to the vertical in a drill press.
An important point here is to go as deep as you dare- I cut untill I see the aluminium/brass start to buldge on the outside (put a blob of JB weld here if you go through/ for good measure)
you do not want to change the size or duration/height of the transfer ports here, in the AAC engines generally they have a little too much duration and size for the apc prop anyway.

I cut the passages in the drill press and then finnished the fine details by hand. A good idea is to machine up a teflon plug that is a slightly tight fit in the cylinder. I do this with white teflon and use a marker pen to colour it black- this way I can set it up to a given height in the cylinder and when I reach that height the bur touches the teflon turning it instantly white- the extra visual clue is a big help in getting the transfers the same and not giving one any more duration etc.

The boost port also exits toards the exhaust port due to the "easy" way the porting is done. I go in with a 3mm diamond bur (DON`T use a carbide bur as the bite and ruin your cylinder) and remove the plating from the top of the passage and then cut the entire passage deeper. Next I use the teflon plug as a mould and fill the top 2mm or so of the port with JB weld and heat cure it. Heating it does two things.
1) it ensures the resin cures very completely (and quickly!) and
2) it makes the teflon expand slightly into the port, which clearances the JB weld away from the piston.

Next I go in with a 3mm ball ended bur and very carefully profile the JBweld material to be something close to 45Deg or so. This angle appears to not be critical. (do I need to say careful when we are talking about an 020???)

Last of all you need to go over all the new edges of the cylinder/ hardchrome plating with a fine diamond stone to remove any burs. this is a very delicate process so take your time!

With these mods (plug and cylinder)you should now have and engine that does about 22~23.5k with the apc 4.2x2 prop and 25% nitro.

Japanman

<duplicated>

D Bronk

Thanks for putting these"tricks" in the forum.My engines have not arrived yet ,hopefully on Monday..Anyone have a few Old ,Cox 0.020 Heads,they want to, put out to pasture?? I`ll reimburse the postage,and ,I promise,I won`t work them, too hard..Going to have to look for some new Heads Too...Who else, is going to Fix-up,, some of These engines..

injunnut1

What is the $$COST$$ for one of these engines ..... that is my only question? THANKS!

Larry Driskill

I have sold a few of the engines at $30 each without the glow plug. They take a Nelson plug.

I'm worried that Japanman's mods and comments may be giving folks an optimistic impression of the .020s.

He has done a lot more work with them than I have done. He has seen more success and he has more faith in their performance potential than I have. But I do appreciate all he has done for me and with the engine. I consider his persistence and results pretty amazing.

Japanman is both a great craftsman and fine engine man, I suspect many folks on the forum are such, but he also really loves to tinker with engines, takes on difficult projects and makes the time to spend on them. Remember his ducted fan effort chronicled on a thread here?

I don't need instant gratification from my hobby, but I like to fly as well as build and the likelihood of quickly getting any quality airtime with the .020 seems slim to me.

As I wrote early in the thread, I have had a few of the engines for some time, but I did not attempt to sell them because, as supplied, they are not very usable in an airplane. I worry about selling folks an engine that is not "a runner", even when they accept the premise that they are, at best, buying an engine kit. The engines may have tweaked the interest of folks that would like a different .020, but have been a disappointment.

Probably, I should have kept quiet when the .020 was posted on the Forum, but thought folks should know it is not a runner. Someday there may be another good .020 that is not in "kit form". Now I think what we have is a cute curiosity that may be either a collectible or a project, but not a bolt-on barrel of fun.

combatpigg

My Feedback: (3)

Larry, I think you should sell them to guys who want to take on the challenge to make one a "runner". Over in the engine forum, there might be some guys who would welcome the chance to buy a semi-finished engine kit. there's probably a few guys here who would want to do likewise. Which engine did you model this one after, or base it on?

I'll be seeing you in a week, go ahead and toss one in your tool box and I'll trade you 1/2 a tank of gasoline for it.

Larry Driskill

Hey Pigg,

Could you email (PM) me your phone numbers? We are arriving on Thursday, unless,of course, one of us tries to carry a tube of Crest onboard, and I will give you a whistle.

Japanman

I`m glad you chipped in with the big pinch of salt Larry!

After doing a few of these things I have become accustomed to the scale and tolerances involved.
So don`t expect to get away with the sloppy fits and rough work you can get away with with big 049 engines

Here are a few more pics.
This is my flying engine. The cylinder on it is the one in the pics above and it would do 23.5K with the apc prop without the muffler and 23 with the muffler.
After over heating it in the cowl a few <too many> times it would only do 22k with the muffler due to the slight drop in compression. It seems the AAC version (these engines also come in ABC) like to be very tight cold. This engine still has a pronounced tightness over TDC but it is obviously not enough any more. I am going to make a new piston for it.

Japanman

Now we get away from the boring run of the mill engines that are actually usefull for flying planes,
I can show off my really fun stuff

I made a carbon prop for testing the engines at higher rpms to get a better idea of where they made their best power at.
using this prop I started to work towards more power at high rpms.

This is my best engine. It started life as a reject cylinder that I thought I had taken too far in the port durations, but then when I opened up the rotary valve a few more degrees and tried a bigger venturi, it suddenly started to get excitable!

I the photos you can see a crankcase which I machined down to raise the crankcase compression ratio. I then tryed various cylinders on it to see how it affected them. Really the biggest effect is to move the power up the rev range e.g it makes LESS power with the apc prop and more with the carbon (3.6x2) prop.
I needed to make my own shorter rod and decided to make my own piston while I was at it. both are much lighter than the stock parts.

After I reached a plato (about 31000rpms) where it seemed difficult to make any gains, I made a pipe and manifold to try and got 33333rpms[8D]

Stefan

Japanman

One more thing, In the first two photos above, you can see two crankcases next to each other. if you look closely you`ll see that in one the window area has been enlarged towards the front of the engine to match the cutout in the crankshaft.
Don`t do this mod if you plan to use the apc prop. If you want more rpms but don`t care about losing rpms with the apc (or bigger )props, then this is a good mod to try.

micron28

My Feedback: (4)

Dear Larry;
I need 3 FORAS 0.020 Glow engines, Do live in Mexico and can send the money via WESTERN UNION;Please. send me Your complete name , and address.Also price of postage
Regards
micron 28

DeviousDave

Just wanted to resurect this thread to get a hard copy of your mods ('cause I know they'll be gone when I need 'em) and thank you for the time and effort you put in to making these engines 'go'. I bought four of them from Larry, one as a gift for a deserving friend, two to modify the heck out of, and one to keep in my collection. These are really cool motors, worth the tinker time to me.

airraptor

My Feedback: (66)

are they still for sell??

Japanman

Dave,
Let me know how you get on. I did some more work on these a while ago and made a new "spec" that runs really well with bigger props. My best one turned my KT 4.6x2.8 at over 17K which blew me away- it makes a lot of thrust with that prop, and seems like a very practical setup for actually flying planes.

I have been really busy lately with work- I promised Larry I would make up an engine for him over a year ago, and still have not got it done.
I think these engines really want a high silicon piston to run perfectly. Don`t get pessimistic about them with the stock piston- it works fine. But if you really want a performer, I think you need to reduce the expansion rate of the piston.
I am ..Ahem.. one of these days .. going to cast up and heat treat some stock to machine them out of. Let me know if you want some, and I`ll send some your way.

S

DeviousDave

Sounds impressive! You might be surprised at how fast you can get the right airplane going with a small prop.... Give your current motors a shot! We are modifying GWS 3-3's on our electrified Micro-Sharks and Rivets and they are knocking on 70mph or so-that's dayum fast for a 16" plane. I tried to run the Graupner 3-3 CAM prop on a TD .020, but I need to make a weight for flywheel effect-it's just not enough prop. I did see that FORA's are being sold on Ebay with a TD .020 plug compatible cylinder, but he's getting insane money for them and I wouldn't feel right supporting FORA after how his deal went with them.

Japanman

The description says they turn better than a cox020 from memory. Unless the ones he is selling have been re-tooled that is a big stretch of the truth-

Larry had some with the head to take the 020 plug. Unless you are going to be running very high nitro, I can see no advantage, as I raised the compression ration of the stock cox plugs by a factor of about 3 when making it into a button.

By the way, if you get desparate with plugs, I found a way to modify nelson and turbo plugs to run about as well as the cox 020 plug- you have to have a lathe and big dose of patience to do it though.

S

DeviousDave

Well..... he didn't say they would out turn a TD. 020, maybe he meant PeeWee?

I'd be very interested in a way to use Nelson or turbo plugs....

Japanman

A peewee would blow one away. Perhaps cox made a rare Babee020? Perhaps he meant a cox 020 retro fitted with an 010 cylinder and running on Budweiser but forgot to mention it?
I have got it. [8D] he meant it will run faster than a cox TD 020 with the same prop and fuel so long as you do not start the TD020 !

I`ll have to remember that one. Look out guys- my modified cox surestart with the same prop and fuel blows away my Cyclon 061*


Stefan

* special conditions apply. identical prop and fuel, engines tested within 30 minutes of each other, same starter battery, same underpants worn for each test, second engine not started, If symtoms persist, see your doctor.

forsakenrider

I just found the 020s on ebay and it got me interested so i found this thread... I see im not the first to find them. Has anyone tried contacting him and asking where he gets the claim of greatness from? I would love to take on the challenge of tuning one of these, they are pretty.

DeviousDave

Larry Driskill may have one , or two, left. He was down to about zero when I ordered mine.

Larry Driskill

Larry (that cute old Texas dude) has a couple of used / abused specimens, but none for sale. He also has a sticky note on the wall above his desk to remind him to stay out of the tiny custom engine business . . .