Turbo Plugs How To
 

Ever have a day when nothing went right and you just wondered why you bothered to try? Ever have one of those days when everything went right and you wondered how it could be so easy? Ever have one of those days when nothing went right,,, until that light bulb went off in your head and welded some appropriate synapses together and suddenly, life was good, there's a god and electrics are just a passing fad? Today was like that.

Thanks to Japanman, we have a solution to the impending obsolescence of millions of Cox engines. Not to mention the agonizing wait for Norvel plugs to re-appear. A secondary BIG honourable mention goes to Stewart, (SGC) for suggesting that stock Norvel plugs can be drilled and tapped for Turbo plugs.

As mentioned, JMan had provided a Cox plug modified for a turbo and also did up a blank I had sent him for the same type of plug. They provided no advantage so I shelved them till I had the opportunity to work with and improve the Brodak/CS engine. When I say provided no advantage, that is NOT a negative,, what I mean is that they were EQUAL to a stock Cox and Norvel plug. Really, a magnificent feat considering that the installation of standard plugs creates terrible gnashing of teeth and wailing about the loss of power. Not so with the turbos and that's the point. We can now make our own turbo devices, kudos to JMan for the Cox version and kudos to Stewart (SGC) for suggesting that the same could be done for Norvel plugs.

OK, here we go.

Initially I couldn't make a good result using Japanman's method of sharpening a common Phillips head bit. So, as related in the first thread on the subject, I found a countersink drill bit that had the correct angle and, along with the correct tap and the use of my Taig lathe, I was able to do up Cox plugs and also make turbo buttons from scratch. Great if you've got a lathe but what if you don't? So, I revisited how JMan did it. On a drill press but using the bit that worked so well for me.

That is pictured below.

First, you screw your plug into a Cox cylinder to act as a holding fixture and firmly, and squarely install that on to your drill press vise.

Then you use a razor saw to cut off the crimp to release the center post. Be sure to dig out the filament. Take out the plug and use a sanding block against the top face to clean it up. Reinstall and make sure the plug is now tightly screwed in.

Then you drill out the plug using the tapered drill. Note the collar to act as a depth stop.

Then you use the 9/32" drill bit for the threaded portion. Another collar as a stop.

Next, use the drill press as a guide to make sure the tap runs dead square into the bore. No, freehand won't do, I don't care how good an eye you've got. It has to be PERFECT. Chuck up the tap very lightly, we don't want it to stick, just use it as a guide. Slide your plug underneath and using some small pliers, draw down the tap and start turning. Note the beautiful chip, just starting. Start it dry, then add some tapping fluid and just work it back and forth by hand till the tap bottoms out.

Once done, clean up the underside with a mounted stone to take off the burr that will develop.

Clean it up thoroughly with soap and water and don't forget to work the threads firmly with a Q-tip. You absolutely must do this, them chips embed themselves into the threads pretty solid.

Finally, the turbo plug has a diameter larger than the bore of the head clamp so this must be drilled out to 3/8".

OK, you're done, you're so smart you oughta president. ;)

But uh, oh, testing it on your engine shows a serious leak. NO MATTER HOW TIGHT YOU MAKE IT. What, miscalculated on the depth stops? Can't be I used a good one done on the lathe as a guide. OK, maybe got it wrong, maybe the threads aren't going deep enough. Drill and tap a bit deeper. Nope, still leaking. What the,,, OK, dress up the seat with the counter-bore,, just a bit,, not too much. Ah sh**t, (shoot) bored clear through. DANG.

OK, start all over again, this time paying REAL CLOSE attention to how deep we go with both bits. NOPE, that wasn't it. OK, try a third, this time using a feeler gauge to adjust the depth, bit by bit. Nope, the *&%$#@ thing still leaks. That's the third plug and now I'm clean outa bad plugs. Oh god, no, I'm going to have to trash a GOOD plug??? At 12 bucks a pop?

This nonsense took all afternoon.

Well, if I have to sacrifice a good plug I'm going to have to sit back and rethink the entire procedure.

To be continued,,,,

RE: Turbo Plugs How To
 

After mulling things over while munching on a sandwich and sipping a coffee, I decided to hit the computer and read some of the past references on the project. It kept creeping up that Japanman had done such a good job on just a drill press, no lathe required. Yet using a drill press I got three duds in a row. And yet on the lathe, no problem. Then it dawned on me. The key was the Phillips bit that JMan used.

The first picture illustrates three that you get in the typical tool kit. At the very first attempt, I used the number 2 bit for no particular reason except that it seemed sized right for the job. It, along with the 13/32" bit for the tap was used but I got leakage so I went looking for a substitute for the Phillips bit and that's when I found the counterbore bit that had the correct taper, shown in the second picture.

By this time I decided that I'd better give myself the best chance possible to get a good result so I went to my lathe. And, I had good luck making all the turbo buttons I wanted, as shown in picture three.

But that doesn't help you guys and that's when I made the promise to reveal how YOU could do it with tools you'd likely have on hand. The trouble is, I made the promise without determining if I could deliver. Well, a promise made is a debt unpaid so I just HAD to figure this out. After all, if Japanman could do it,,,,

SO, as it turns out, bit number three is used to cut the taper AND the bore for the threaded portion all at the same time. Yes, it's not a cutting bit but here's the deal. Get yourself a brand new one, one that has never mated with a screw. Bad imagery, I know. Anyway, use a fine stone or a sanding block with 400 grit to dress all the cutting edges. You don't have to make them razor sharp, just take off any burrs or imperfections. Pay special attention to the taper portion. Get it nice and shiny. Try not to alter the taper. With care and a light touch it can be done.

Picture four shows all the tools you'll need. The number 3 Phillips bit, the tap (M8 X 0.75 bottoming) and a 3/16" drill bit. The latter is only used as a go, no go gauge.

Use the Phillips bit to drill the taper AND the bore for the threaded portion. This is the key. In the previous set of instructions, doing the bore for the threads separately on the drill press did not guarantee that it was on the same line as the taper seat. The accuracy of the lathe assured this,, not possible free hand with a drill press.

Picture 5 and 6 shows the Phillips bit cutting cleanly and effectively. The key here is to go slowly and to use the 3/16" bit as a go, no go gauge for the hole at the taper. Yes, this is tedious but the point here is to get a good result first. Once that's done, you can use the good piece as a gauge to apply the collar as a stop for the next batch you do as in picture 7 and 8. You ARE going to make a bunch of these aren't you? No sense letting the expense of that tap go to waste. :)

Once again, use a mounted stone to deburr the underside and from here follow the steps in the first set of instructions.

Success !!! :D !!! What a delicious feeling having the prop snap over smartly indicating a perfect seal. Testing with a bit of oil at the plug interface shows no bubbles and gentlemen, finally, we HAVE it.

Continued,,,,,

RE: Turbo Plugs How To
 

OK, that's great and this Cox/turboplug assembly can be used on Cox AND Norvel .049 and .06 engines. But what if you have a Norvel .074 or even the CS/Brodak engine? As in the Brodak engine thread, MUCH free power can be had by installing a Norvel plug or a turbobutton.

Well, thanks to a suggestion from Stewart (SGC), I had another look at how this could be done without a lathe. Normally, you have to make a button on a lathe. This, I thought, would be necessary because the stem of a stock, Norvel plug is just too small in diameter,,, not enough meat. Well that was determined by eyeball and I was wrong. Now you can put to use all those blown, fried and just plain worn out Norvel plugs.

Here we go.

First picture shows a stock Norvel plug secured in a vise and the crimp being sawn off to remove the stem. Just work the blade round and round till the whole mess pops off and pull out the filament. Dress off the rough, top edge with a file and then, using your Cox, mounted in the vise cylinder, secure the blank with a Norvel head clamp.

Then proceed as normal. You'll find that the wall of the threaded portion looks to be way too light but so far it holds and the plug seals nicely when it's screwed in quite firmly.

For Norvel .074 buttons, do the same except that you're going to have to use a kaffed Norvel .074 cylinder as a holding jig. DON'T use a good one, you'll ruin it, the bottom stem will likely get distorted in the vise. No, this isn't a don't ask me how I know deal,,, just don't take the chance.

And there you have it, turbo plug devices for your Cox, Norvel and CS/Brodak engines. Turbo plugs come in a variety of brands and heat ranges. OS has three from cool, to medium, to hot and Rossi has eight from extremely cold, to extremely hot. Now you can pipe that Norvel to 40K on 60% fuel without blowing a plug on every flight. [X(][X(][X(]

RE: Turbo Plugs How To
 

Andy Thanks for This!! Here`s just an observation..see the pic ..Maybe the Rpms of the lathe,opposed to the Drill press,For useing the Center drill,is an issue?Possibley ,the amount of cutting edges, on the Simple phillips bit, is keeping the Taper ,to the hole ,more Square.If you have a dial indicator,Check your drill press Spindle, is not wobbling.It really makes no sense ,if the Center drill is the correct cutting angle,You should end up, with a leak free seat..I know the cheapest ,easiest method, is with the Screw Tip.Sure is a strange thing though.Could there have been, tooling marks, in the glow plugs` taper ,causing a leak?The thing is ,why would the Center Drill work in the lathe ,but ,not the Drill press??Very odd.

RE: Turbo Plugs How To
 

My pleasure Dave. Thanks for the input and those are good points but,,,

The seat is actually OK and in perfect alignment. It's the threaded portion that can be off center. The stem of the counter sink bit is too small to bore a hole big enough to accept the tap. Therefore, you have to drill out that portion with a larger diameter drill. On the lathe, everything is held firmly in alignment. Doing it free hand, with the drill press, it's just too easy for the vise to wobble, walk, shift etc. Note that the final drill bit is not that much larger than the shank portion of the countersink bit. So there's not much material to force the drill bit to center properly. On the lathe, all is in much better alignment for the initial lead in of the drill bit. Also, the issue IS the tapped portion because the counter sink has a pilot tip that starts exactly on center and guides the taper to cut exactly square and in alignment.

Real machinists must be shuddering and tsk tsking at the use of the Phillips bit and maybe it shouldn't work but it does.

In any event, some corrections and additions need to be made.

Item one is that you should use a countersink bit just to get the initial cut started. Then switch to the Phillips bit. It's not such an issue with Norvel plugs, but is a little more critical with Cox units.

Item two is that you want to start the Phillips bit dry to get a feel for the way it cuts and to make it easier to clear chips. As you approach the end of the cut, DO apply some cutting oil to give the tapered seat a good finish.

Three, I ran across a Phillips bit of another brand that was quite dull in the "cutting" edges. Guess I got lucky with the brand I started with. If you have a dull one, get another or DO sharpen the appropriate edges taking care not to alter the taper. If you've worked at sharpening cutting tools you'll know the edge to work on and the edge to leave alone.

Item four is the go, no go gauge. The 3/16" was suggested to make sure that you don't go too far. Like a haircut, you can't put any back. The final cuts will have to be with oil and are incremental. You get a feel for it and you can feel the bit cut a bit and you back off, take it all out, wash it and then test fit your plug. Running the plug in by hand won't do, you have to tighten it up firmly to get a good, sealed fit. Use oil, see below. Once you've got it right, (and that turns out to be EXACTLY 4.8 millimetre) you can use your good piece to set the location of the cutting bit's stop collar for all future jobs. Even then, you may have to tweak and fine tune. DO have lots of dead plugs to fool with.

Item five is that you DO want to put some lube in the thread and on the taper when installing the plug. Remember, you washed out the piece and if you install it dry, there's a chance of getting some galling and bits of metal falling into your engine when you take the plug out. Ask me how I know. [:@] With lots of lube, tighten and loosen the plug a few times to help seat it for a perfect seal. Your final task will be to clean out the bit of black this creates on the tapered faces of both pieces. Once seated, this effect no longer occurs but do make sure you lube the plug JIC.

Finally, making a drill bit of the right diameter with the proper taper tip is kind of beyond my skills and the tools I have. And the point of this thread was so that anyone can make their own turbo adaptors. Myself, I only have a simple Taig lathe with attachments and some home made fixtures. It's really quite primitive. I would love to upgrade but I'm waiting for the Chinese to offer a complete CNC shop, You know, turning, milling, grinding etc with an accuracy of five ten thou. for 500 bucks. [X(] The way things are going, you never know. ;)

Here, http://www.rcuniverse.com/forum/m_44..._2/key_/tm.htm classicalgas, (Bob) showed how he made adaptors to take Nelson plugs for Cox .020s. Thanks Bob, that gives me some ideas. Which will be the next item to tackle if I can get the proper die cheaply enough.

That may take care of the .020 but what concerns me a lot is a source of plugs for my precious TD .010s. :(

But now that we have silicone tubing in very small sizes that resists diesel fuel, I just may go all diesel and not ever have to worry about plugs again.

Nahh, no fun in that. :D

RE: Turbo Plugs How To
 

Andy; once I get my mitts on a couple turbo plugs(have to order some now)..Maybe I can grind, a drill bit for you,to experiment with..I realize, the thread is for, the average guy ,with minimal tools,but a bench grinder, and a Drill bit ,is something most fellows have near by,with a drill press, too.Would kind of like to see, what you could do with that bit.I don`t have any Glow heads ,or buttons to try this out for myself, YET,or I would..It`s definately nice to know, that once ,the factory made stuff is gone, or burnt out,We have a solution,to keep our little engines going.:D

RE: Turbo Plugs How To
 

I have just looked carefully at a Nelson plug and 049 adapter.

If one used a lathe, it looks like the diameter of the threaded portion of a Nelson plug could be turned down. The tapered seat face could be reduced by about 1/2. This would then allow you to re-thread the outside of the formerly threaded portion, down to a size to fit a newly designed 020 head adapter or even a used 020 plug itself. The question is how much meat is there inside the Nelson plug to for allow this reduction in diameter? Is there a large cavity for the stem sealing material such that there would be no material after turning down the body?

What about the turbo plugs being similarly turned down to a suitable smaller diameter for 020 or 010 use? I don't have any Turbo plugs to examine. Would a conventional glow plug be small enough for the 010? I am looking at one and it appears small enough in the threaded portion. Has any one used a conventional short plug and made up an 010 adapter?

Just some thoughts on a quiet night.

Jim H

RE: Turbo Plugs How To
 

how, great job.

I have a suggestion.

Is there a way that we can archive all of these various machining threads so that way they can be stored and not get lost back in the back of all of the posts? There is alot that you guys have done that I would like to try one of these days, but I fear by that time these threads wont exist anymore.

RE: Turbo Plugs How To
 

Sometimes you have to cut and paste or even print out the really good stuff and save it yourself. I've got a drawer, a shelf, a few odd stacks of paper and several files in the computer for reference and future project stuff as well as having many web sites in my favorites list. Its them oddball hand written notes that I'm apt to leave lying about that keep getting lost.

RE: Turbo Plugs How To
 

Great work Andy, funny how simple tools work out better.
Just a thought for those with no dead cylinders to use as a drilling jig, leave the cylinder bolted/screwed onto the crankcase and grip the crankcase front to back in the vice- dont forget the softjaws!!!, to do this you will need the crankshaft removed, but no probs you will need to clean it anyway.
Stewart

RE: Turbo Plugs How To
 

Andy,
Just found this OS plug chart, on which they list 4 turbo plugs.
Stewart

RE: Turbo Plugs How To
 

Hi Dave,

My concern would be to get the correct angle and rake,,, if that's what it's called. Such a bit might have too much bite and snag. You can see the logic in the way they make the counter sink bit. And, the Phillips bit also has this limiting factor. BUT you never know. No doubt though, that the engine makers that offer this type of head have precise, custom made tooling.

RE: Turbo Plugs How To
 

Jim,

Some interesting ideas. The problem with any kind of adaptor for the .010 is that the relatively large cavity compared to the stock plug would add that much more volume to the combustion chamber. This could be corrected by facing down the plug, of course.

Use of a conventional plug in any sort of adaptor guarantees a large loss of power, unfortunately. This is why the turbos are used, they don't have that flaw. That's a good idea to turn down the body of a turbo plug and re-thread it. But while the .020 Cox head has enough meat in the diameter, the length doesn't give you a lot of threads to work with. An entirely new adaptor really does have to be made from scratch, as per the link.

But both heads are so small,,, what may happen is that CS, who bought Cox's tooling, may just be able to make these plugs for us at a better price. We can hope.

RE: Turbo Plugs How To
 

You guys might be forgetting that the average 'home shop' drill press is not worth a damn for doing any sort of 'Precision' machine work. Why you ask? Even though the spindles are probably running close to true, remember these relatively cheap drill presses are using bottom of the line EL CHEAPO chucks ..... any drill press is no better than the CHUCK that it uses. This is why a GOOD professional chuck will cost probably three times as much as the average 'home shop' drill press ..... just chuck up any longer drill bit in your drill press ..... now turn on the switch and watch it wobble like crazy at the tip!

RE: Turbo Plugs How To
 

" now turn on the switch and watch it wobble like crazy at the tip! "

Who says you can`t drill an Oval hole.:)From the pictures Andy posted, it looked like he has a Jacobs Chuck,on his press.I recall Those, as being one of the best..MayBe the 6 sides, on the phillips screw tip ,help to keep it running true ,too,plus it`s very short,and stubby,and can`t really flex much..Just ,something else to wonder about.

RE: Turbo Plugs How To
 

Injunnut, Dave,

Gotta contradict both of ya. Yes, it's a Jacobs chuck, the drill press is not one of those 50 dollar Chinese jobs,,, it's domestic, bought some 30 years ago and it cost me the price of a radio. No tilt table but I like it that way. Annoying is that it won't cinch down on 1/16" but WILL do up to 1/2", or more.

Now, despite the chuck being a Jacobs, when I cut using the Phillips bit, I get a slight wobble when it's cutting. Huhhh, how? Why? Well, the Phillips bit, instead of the press, IS one of those Chinese deals.

Despite that though, the idea is that the bore for the threaded part is cut at the same time and exactly on line with the taper.

I'm speculating that Japanman, living in, well, JAPAN, has got both a quality press and also bits made in Japan. On the other hand, my SONY Walkman is made in,,, CHINA.

And as the world turns, today is SO different from yesterday. When I bought my first car, a Datsun (Nissan) 36 years ago, I was laughed at by the guys at work. You know,, Japscrap, like that. They stopped laughing some 13 years later when, with 240K miles on it, the engine STILL purred like a kitten, burned NO oil and the cam lobes were not worn at all but just smooth and shiny on the working surfaces.

BTW, Stewart is one right smart guy. When I commented on how poorly the hemi head worked, he explained how squish bands worked and that too MUCH of a good thing is NOT. So, experiment but a hemi head in these small sizes is likely to disappoint. That comes to mind the trumpet head that seemed to work best. As with props, the original Cox folks knew a lot about what works. Notice that the Cox high compression head is trumpet shaped.

Also, classicalgas advises that he makes up turbo heads for vintage glow engines and that this adds some 400 RPM on those and up to 1000 RPM on modern engines. WELL, I guess I'm going to have to make up a turbo head for my hybrid OS .10 and see what happens. Maybe make a trumpet head AND a stock head. Let's see,,, that's number 23 on my list of things to try. Can't believe I'm so bloody busy,,, hell, I had more time when I was working. [:@]

RE: Turbo Plugs How To
 

I think that cutting the taper,and, bore in the same opperation IS the Key..Stewart is Right, about the Squish ,on, a Hemi head though .The Best working example I can give ,is on my Early mod. Race Sled.Its a 1/2 mile,ice oval Racer.The Engine is a 340 c.c.,Hemi head, Twin Cylinder ,Rotary valve,Rotax,Free air cooled,with dual Carbs,and, Twin tuned exhaust pipes,exiting out of stingers The Engine is ported and polished,The Crankshaft runs on ball bearings,and the Rods are on needle bearings @ both ends..The engine is extremly perticular about it`s "Squish"..It needs to have, exactly 0.006",between the piston top and the "Squish Band" ,at the bottom of the head.If the cylinder head is any closer, Detonation occurs,,,any further away ,and, power is lost.....I have an appointment to attend, this morning,When I get back, I`ll look for my Books,they have some good illustrations ,and explanations, about Squish ,and, 2 stroke Hemis.I`ll scan them ,and upload ,if anyone is intrested in seeing them..Let me know

Andy; Which is the Glow plug,that works best for These Small Norvel adapters..I think I can get, the majority of the O.S.plugs, that are in the chart above,that Stewart posted.,or is there a couple heat ranges, I should get to experiment with?? Part #`s please..I want to order today..Thanks Dave..

RE: Turbo Plugs How To
 

Hi Dave,

The OS plugs were supplied to me by Japanman at the time he sent me the pieces he made. I was unaware of the super hot P3. I found the medium to simply work the best along with the trumpet or the stock head shape. The hemi was the worst one of the lot,, but I only took a guess at the volume. It would take an afternoon of adding/deleting shims while running all four plugs on various nitro fuels and LOTs of data recording to make a proper scientifically valid determination as to the best plug to use. And of course, if you add or delete shims to adjust for volume, you're changing the squish band and well, there's another variable to consider. I can see that one could make up four hemi buttons with varying hemi volume and then, do multiple runs while adjusting shims. Add to that, experimenting with heat ranges and differing nitro content and well, LOTS of R&D fun with lots of data to crunch.

I fried my P6 (hot) and I recall that it did well. Went the next up, P7 and it works fine. The P8 sounded a bit off, but I never really made any radical needle adjustments. These days, (summer) I get a bit lazy and just go for it if something works.

I'm going to get the two in the ranges that I'm missing and do a thorough evaluation of the usefullness of each, one day, on my new .074. This WILL have to wait till the fall though. That sunny, warm weather beckons,,, you know 6 months of winter,, got a lot of fresh air, sunshine and flying, beach and fishing to catch up on. :D

Crazy thing is, I look for a rainy day so I can catch up on shop work. Go figure.. :eek:

RE: Turbo Plugs How To
 

Well I guess that,I`ll order all of the P- series,1 of each ,and do some experimenting too. Thank you ......Dave

P.S. enjoy the season ,it doesn`t last long.We go from one extreme, to another, here.It goes ,From everything White ,to everything Green.....LOL

RE: Turbo Plugs How To
 

Yeah, but as we both have our own ski designs, the white don't stop us do it?? If I can find that clip of the Mini-Sport on snow,,,

RE: Turbo Plugs How To
 

YES, please do let us have that data on squish band. It also seems to work on diesel engines as one diesel button I made had a bit smaller than normal contra-piston and it seemed to give a smoother run than the other on my .074. So I made one with a MUCH smaller CP but this one was the worst of the three.

RE: Turbo Plugs How To
 

Just popped back in, for those O.S. numbers..I can`t believe the price[X(][X(][X(]. almost $15.00 each.Most of them use some platinum, but these,must be made from solid platinum[:o].Just going to get a P-6,+P-7 for now...OWwwCcchhh[:@] I`ll look for my book after I`m done ordering ,I`m not certain where it is, at the moment ,but its here somewhere. Dave

RE: Turbo Plugs How To
 

" I can`t believe the price . almost $15.00 each. "
Ye makes Nelson plugs at $4 look good hey.
Dave,
Your racer ? does it have dome topped pistons ? From my 2st experiance hemi combustion chambers work best with dome topped pistons, were the piston top has a smaller radius than the combustion chamber , this gives a natural progressive sqish band and makes the motor not prone to detonation. Oh and how many souveneres do you have hanging in your shed ? Full combustion detonation makes nice 10-30mm holes dead centre in piston crowns hey:)
Stewart

RE: Turbo Plugs How To
 

Owwch is right. Sorry guys, I had no idea. As I said, JMan provided the plugs way back. So I checked around and yes, I've been quoted up to 17 dollars Can$ for OS turbos. I really like the OS product, they have a very professional, clean, quality look. But price,,,

So I called around some and an outfit called Team Orion offers turbos for a much cheaper price. How well they work is the question. Here's one place to get them.
A Canadian shop in Barrie, (Ideal Hobbies) has them for 8.99.

http://www.rcplanet.com/team_orion_06_t_49689_prd1.htm

This one is reco'd for fuel up to 25% nitro.

http://www.rcplanet.com/team_orion_05_t_49686_prd1.htm

RE: Turbo Plugs How To
 

Andy,
With that small contra diesel button, first try cutting a 5thou recess across it the full cylinder dia. Then refit and run it to find the new contra possition. Then make a taper cut from 50thou in up towards the contra, but only 1/3 the height, then give it a run.
Stewart