Larry Driskill

Infamous? Infamous? Wow, except for the fact that good old ptulmer had seemed like such a good a good guy and positive contributor here, his throwing out identifiers like "infamous" rather than "clever, sought by the babes, and talented too" would make me think he might really be the corpulent attack dog Ted Kennedy using an alias.

When we started using AMEs they would often seem to go lean soon after launch. But when you picked up the plane (after the engine died from the seemingly over lean condition) the bladder fed needle would still be putting out fuel at the normal rate. But the engine would be very hot - just like you would expect from a lean run.

After it cooled you could fire it up and the needle setting would seem fine, even though you had not changed the needle. Launch again and you would again get the few good seconds of run and then . . . lean again.

In spite of "clever, sought by the babes, and talented too", I was slow to solve the problem. The engines usually got better after a whole bunch of tries and flights, if you stuck with it. Then I realized that the engines were overheating from the bottom end vice from being too lean. The shafts were fitted too tight in the crankcases and when the engine began to warm up the clearance decreased and friction increased causing more heating and it was all downhill until the shaft seized in the case. I finally figured it out when I checked out a shaft and found aluminum on it where it had galled in the case.

I cleaned off the aluminum, lapped the shaft in the case with Bon Ami and oil and viola! Problem solved.

The next step was to put a shaft in the lathe and use emery cloth, followed by 400, 800, and 1200 wet / dry paper with oil to remove a tiny amount of material from the center portion of the shaft. The surface of the shaft behind the port opening and the front 3/16" was left alone. This reduced drag between the case and shaft, but left the front and rear bearing surfaces untouched.

And so . . . especially with plain bearing engines, it may well be that a careful fitting followed by an equally careful bench break-in to the point where you are sure the engine will hold a good, top end needle without overheating and stalling is good practice and will help prevent unwanted dead stick landings. If the engine does not hold a setting on the bench, it probably will not be any better in the air.

Burma Shave

gcb

Viola?

Several years ago some folks (including George Aldrich) were talking about mixing tops and bottoms between the AME .049 and .061 to get a 'tweener size that would still be 1/2A, yet have a little more displacement and performance.

Anyone ever try this?

George

Larry Driskill

I built some AMEs using .049 piston/sleeves with .061 cranks. The .049 are really (were ?) about .0477s (bore .400 and stroke .38). The .061 crank (stroke .39) stroked them, but not so much that they were larger than the legal .0504 limit.

rtc_71

whats a good prop for a norvel .061?

Andrew

Larry --

Need I remind you that RCU has a stated policy against such posts.

Please resist the urge to curse, flame, degrade, insult or embarrass someone in your post. We encourage the free flow of your ideas, but believe that they can be communicated (and received) much more effectively if you keep things civil. If you have to vent, take it offline. We carefully monitor posts and will ban individuals who engage in offensive conduct within the forums. Thanks.

Larry Driskill

Depends a bit on: the plane, the fuel, the altitude, the particular engine, the weather and so on.

To go fast you need some pitch, maybe 3.5 or 4. But you still need RPM so you will not be able to use much diameter. So on a lightweight plane - maybe a 4.5X4 and increase / decrease the dia and pitch from there to optimize.

For "pulling power", more diameter and less pitch. Maybe a 6X2 or 6X3 to start.

Larry Driskill

Andrew you are correct. I've transgressed and I apologize to canines everywhere for the association I made.

Andrew

ROTFLMAO

rtc_71

thanks larry big help

Larry Driskill

I am pretty sure I have posted this somewhere before, but would have been sometime ago. It is from my "Tips for the VA MKII", but most will apply to the Norvels too.

The abridged version would say: Buy clean fuel -Keep it clean; use enough nitro to help keep the needle setting broad (15-30%); use all castor for the oiling duty (20-22%) or at the very least 1/2 castor; to make their best power, these engines need to wind up tighter than the Coxes - don't over prop; make sure you have a good starting battery that will glow the plug element a bright orange; be really careful using an electric starter or you will break something.

"1/2a flying is great fun. In no other engine class do you stand to get so much airborne time for so few bucks. No other class of gas powered model is as likely to bounce rather than break when the ground smites the aircraft. However, when compared to larger equipment, 1/2a engines and planes are more subject to the whims of the weather and nature and less forgiving of inappropriate technique. Clean fuel, hot starting batteries (with the Nelson plug 1.5 volts is nice), fresh glow plugs, and attention to detail are rewarded.
As with many ABC engines, most VA MKIIs may seem ready to go after only one or two runs. However, do the new engine a favor by putting half a dozen two minute ground runs on the engine before launching off into the clear blue. Needle settings for these runs should be just on the rich side of peak RPM and with a small prop. Avoid sloppy rich runs will not allow the engine to heat up properly and put extra stress on the rod and crank. I use a black Grish 5x3 propeller cut to 4" and fuel with 20% castor oil and 30% nitro for break-in. For better front end lubrication, and easier starting put a drop of light oil just behind the prop drive washer before you start flipping. This is especially important on a new engine and is also a good practice for the first flight of the day even after the engine is broken-in.
Proper head clearance is magic when consistency is the issue. The engine is delivered with .006" to .010" clearance above the piston at TDC. Those numbers have worked well in many situations. However, if you are blowing plugs, the head is probably too close for your fuel / weather condition and an additional head shim may be needed. Start with an additional .002" or .004" shim.
Before installing a new glow plug, smear a small amount of Permatex anti-seize compound (part number - 133a at auto shops) on the plug threads. This will help keep the steel plug from seizing in the aluminum head button. If the plug seizes, the head button will slip and turn under the retaining ring when you attempt to remove the plug. If you can not get the plug out you may have to remove the retaining ring and head button from the engine and hold the button while you remove the plug.
If the engine ever feels as though there is a compression leak, check carefully for leaks around the plug and the head retainer. Light oil or WD-40 will usually bubble if there is a leak. If there is a leak, make sure your plug is a Nelson Standard (no machined cuts on the flats of the hex), or a recently purchased HD, and also tighten the plug. If a black "liquid" shows up in the exhaust oil there is probably a problem. Stop running the engine and investigate. The cause may be a piston that has backed off on the wrist pin carrier.
If you use an electric starter make sure the engine is not flooded or you may bend the rod or break the crank.
Top performance depends on using the proper propeller. When choosing the prop remember that these engines need to turn up higher than older style engine to be in their proper power band. Some 1/2a props of the nylon and plastic cast variety have crooked, out of true hubs. If the spinner / prop bolt is wobbling, true up or discard that prop.
Compared to a .36 or .40, these diminutive fellows use so little fuel that there is little reason to use fuel that may have inadequate or inappropriate oil. Use fuel with 20%, or greater, castor oil. In the VA, castor oil based fuel will make more power and promote durability. The use of fuel with low oil, or only synthetic oil, will most likely result in premature wear of the wrist pin end of the connecting rod. Just because you have had good luck with a particular fuel in your .40 RC engine does not mean that fuel has a appropriate oil content for a plain bearing .049. Keep your fuel clean and tightly capped. I filter mine when I put it in my pitbox fuel can and again as I draw it from the can."

Andrew

Larry -

Would you or one of the other speed gurus post some comments on changing deck height and how it can impact performance.

AndyW

My Feedback: (1)

Best prop for any sport 1/2A is still the Cox 6 X 3. Lower rpms but better thrust. For sport applications you really don't need excessive rpm.

Amazingly, I've found that the black "rubber ducky" props perform nearly as well as the greys and as a bonus, nearly never break.

AndyW

My Feedback: (1)

Depends on the prop brand. An APC 7 X 3 and a Grish Tornado will not turn the same rpms and performance will not be the same. For sport applications, the best prop that I've found for the Norvel .074 is the Cox 7 X 3 1/2. Like the 6 X 3 on the .049/061, the Cox prop will turn slower but the THRUST will be there,,,, for sport applications.

This does not apply to a "need for speed" although, in a sport plane, the Cox will sometimes out fly some other brands spinning much faster.

Pictured is a collection of 8 X 4 props tested on a dieselized Norvel .074 on the same afternoon on the same plane on the same fuel. The Cox actually turned faster than the APC and also out pulled it, in this case.

The issue, when dieselizing an engine and going one prop size up, is that the up sized prop is built for the rpms (faster) of the next sized up glow engine. As those rpms are much higher, compromises have to be made sacrificing efficiency for just keeping the blades attached to the hub. Cox props take the Clark Y airfoil all the way to the hub. The APC goes VERY symmetrical for nearly a third of the blade. Grossly inefficient,,, but they'll never break. Somehow though, Cox props, despite the "thin" blades near the hub, stay together just fine. I suspect that most props are built with a 3 or 4 to one safety factor, just to keep the lawyers away.

I've taken APC props and carved the blades flat all the way to the hub. The result was a free 500 rpm along with extra thrust and efficiency. I've done the same to Grish Tornados and the result was the same. Recent experiments with the newer Master Airscrew props have given similar results. I disliked the old MA props but the newer ones are much better, particularly the wide blade series.

I DO NOT recommend modifying props in this manner unless you're prepared to take responsibility for doing so. In other words, IF you do it, be careful, as always, and in any case.

Also pictured is a collection of 6 X 3 props. You can see a variance of prop shapes and prop blade area. All of these factors along with the plane you're flying determine the best prop to use. Props are cheap, best to get a pile of them and experiment.

burtcs

One of the things I noticed with the early (second generation) AME's was that the needle valve was very touchy. I was running them on the bench with surgical bladder tanks or balloon bladders and I only had about 1/4 turn of needle valve from too rich to too lean. The other thing I noticed was that given a 12cc charge of fuel I could never get a consistent run much longer than fifteen seconds. The engine would start too rich, lean out to perfect then go lean as the pressure dropped. This is why I hate (such an ugly word) bladders.

I removed the needle seat from one of them and the cross-hole was 0.055" - wow. No wonder it was touchy (what are you combat guys doing???). I realize the cross hole is partly a function of the needle valve threads; I soldiered the hole closed and redrilled (use a pin vise) with a 0.032" hole. This gave me about 1/2 a turn - mo betta. I tried another with a 0.0.025" hole and this gave me about 3/4 of a turn. If you're using a CL/FF type engine you might try this. Might there be a more optimum size? I hate spending another 10-15 bucks for a fine thread needle valve or dorking with them every time I buy an engine.

Others may have pushed the envelope further so OF COURSE I'm always open to new info. How are you controlling the pressure? I know FAI FF guys are are using long pieces of latex tubing maybe 4-4 1/2". Same story or maybe a small orfice?

Regards - Steve B.

Larry Driskill

Steve I had the same problem with Norvel needles. I think the threads are too course and so one click is a bunch when your fuel is under a good deal of pressure. I used to modify the brass Norvel needles by installing a 128threads per inch KK needle body inside the brass body. It was a lot of work, but solved the problem. Later I installed VA needle assemblies (110 TPI) in the Norvels. That also worked.

Bladders need a fine threaded needle and the bladders needs to be low pressure. For 1/2A I use thin wall latex (about 1/32 wall).

Bladders can be made to work as shown by about a gazillon successful CL Combat matches flown since back in the 1950s.

Larry Driskill

I am slammed a bit with work and need to contemplate and find some free time to come up with a good answer on deck height.

In the mean time, here is a site with some info.

http://www.rcboat.com/cr.htm

burtcs

I have a handle on 0.049 and 0.061 AME's, Stels and to a certain extent MKI VA's but now I'm grappling with a different beast. I just got a Norvel Big Mig 0.074. I am trying to get it broken in. I don't think I've wrecked it yet and in truth it's feeling better than when I started but I do have some questions.

I read the prep sheet and let the engine steep in 30wt motor oil; I did the 100 flip ritual and then tried to mount it up to my test stand. I had to pull the muffler for clearance so no pressure to the tank, only suction. It can be done if I opened the needle up SEVEN turns. I mounted up a 7-3 APC.

I've never liked Norvel glow heads and have always been able to use a Cox high compression, a KK head with Nelson plug or more recently the Galbreath head and Nelson glow plugs. Norvel heads always gave mediocre performance and with this engine I have nothing to compare with. The plug (158) seemed cold, I had to crank the power panel (I tried three of them, same story) to it's max. setting to get a crappy glow. I'd have blown other plugs a long time before that.

With three head gaskets, 15% Nitro per Norvel was a bust, no pop or bump of any kind. I broke out a starter and still no joy. I finally dumped the 15% and filled the 2 once bench tank with 60% nitro. The engine began sputtering but it won't run with out the starter. Towards the end of that first 2oz. tank it would run with very low RPM's for maybe five seconds and die. With 2 more ounces of 60% nitro loaded up it would run by it's self at maybe 800 RPM unless I tried dorking with the needle valve or throttle. By tanks end it would buzz up to about 8500 RPM.

I refilled the tank with 35% nitro and was now seeing some throttle and was up to about 10k RPM. I stopped there, it was too dark to see the tach and I want to build an adaptor gadget for the stand so I can use the muffler. I can't think of anything else except for burning out the original plug and replacing it with a fresh on which didn't glow any brighter. The power remained applied to the button during this hole thing.

Is this normal? Or...Is this engine really a joke like another 0.074 I could mention? As noted the engine flips over smartly by hand but it's not starting that way - only with a starter. I pulled the head and back plate last night and everything still looks ok. I'm prepared to carry on doing what I doing though this does seem very strange. Might this just be part of the joy of 0.074 ownership?

TIA - Steve B.

Bipe Flyer

No, that is not normal. The Norvel .074 is one of the nicest running engines in any size. It throttles as well as an OS and has a lot of power for its size. It also has a much lower idle than the .061. To break mine in I just put them in a mount, set the needle 3 turns out, prime and hit it with the 1/2A starter. I've never had any problems with the plugs, in fact I think they're better than a standard plug. I use 15% Nitro 20% Castor fuel and an APC 7X3 or MA 7X3 for break-in. I have a BigMig .061 that runs with no muffler or pressure and it runs fine, so that probably isn't the cause of the problem. What fuel tubing are you using? I find that 1/2A tubing is too restrictive, so I use medium.

KidEpoxy

Heck, I skipped the soak, few plughole drops afterrun oil & just worked the 100 by hand then mounted it
25%, ~4 turns, Prime, Clip, bump with starter, run & tweek needle to sloppy it for a min or two, then just rich.

Call me crazy but I used the muffler pressure and it worked just fine. Havent tried it without the pressure, and don't see a reason to (for me). If you are having a bear of a time without the muffler.... try just breaking it in with the muffler

burtcs

BF & KE: Thanks for the words of encourgement. As soon as I get an extension for the test stand made up the muffler is going back on. It won't fit right now because of clearance issues. What size mounting bolts are you using. A 2-56 just rattles around, a 4-40 will require drilling.

Thanks - Steve B.

Bipe Flyer

I use #2 screws.

KidEpoxy

And I used the drill
Looks like between Bipe & Me you pretty much cover the feild, Bipe did everything right, I did everything 0.5 azzed - Both got it done, kinda is a testament to the Lil Norvies

burtcs

BF, KE et al: I set the engine up again today, this time with the muffler in place. I opened the needle up to four turns, 35% nitro and 7-3 APC prop. Weird but true it's not a whole more quite with the muffler than without it - but there's tank pressure. It sounded more like a diesel. It did kept the test stand cleaner though. Pretty much the same story as last time - not very much RPM. Today the engine was pulling about 8700. I refilled the tank with 60% and got it up to 9700.

Since I was throwing the prop (a common AME trick) alot with the starter, I decided to change the prop for a softer one. I installed a Cox 6-4 - what a difference. I made a couple more runs and could get the little weasel up to 16k. It actually sounded like a glow engine. I ran out the 60% and refilled with 35% and was still getting up to 15.5k with a nice peaked sound and light smoke/oil from the exhaust. Running slightly rich yielded about 14.5k. The needle was working, the throttle was kind of working and I was running on and off without glow heat.

The final numbers at the end of the day were: 4 head gaskets, Cox 6-4 gray, SIG 35% Champion with 1 1/2 ounces extra castor and 2 3/4 turns of needle. Max throttle 14.5-15.5k and idle at 10k. I kept adding head gaskets from two to four hoping to drop the RPM abit with no such luck. It needs a larger prop diameter to slow it down. Hand propping yields popping noises but I think my fingers are safe - it's not going to start without the starter. So far I've burned up 4 ounces of 60% nitro and 5 ounces of 35%, fried a glow plug and lost a prop bolt and spinner.

Tomorrow I'll try 15% and try a different 7-3 prop. My question of course, is it there yet? I think it's close. Is anyone using a norvel starting spring on the the 0.074?

Thanks - Steve B.

burtcs

The rain finally stopped yesterday and I went out to run my NEW but by now well flogged Norvel Big Mig 074. I started with a 7-3 APC, 15% Nitro, and 2 3/4 turns of needle. It started and groaned away never exceeding 9,000 RPM. Idle was about 5500 RPM. It now runs on 15% but It is quite clear this engine doesn't like 7-3 props.

I refueled my 2-Oz tank with 15% nitro and changed out the prop to a Cox 6-4. The engine sounded like a two stroke again revving up the 15k. It needed 4 turns of needle. I started monkeying with the head gaskets but I didn't see or hear anything that would suggest that it was making any difference - I'm down to one. Idle is about 10k, this carburetor is a joke. I'm going to dremel out the throttle arm to get a little more closure when the weather gets better.

I did manage to hand start the little beast by raising my rubber tipped chicken stick over my head and smacking the prop. I did this once (only). This engine will need a starter.

It may not be very nice to compare this engine to others but just as a point of reference my OS 10 FP will turn a 7-3 up to 18k. I've got an ancient OS 099 pet that will turn a 7-3 at 17.5k. Same prop come to think of it. It's been a long time but I don't think my Cox Queen Bee did any worse than this thing. I'm going to break it out for a run.

An associate warned me that I would need to pull the head and just grind on the engine with a stater for about 5 minutes, then try to start it. He was right...

Thanks - Steve B.

combatpigg

My Feedback: (3)

Burt, a well broke in .074 should give 17,000 with a 7x3 APC. If your engine is too tight, it will display the characteristics that you describe. I would continue to break it in with a 5x3 prop, in a slightly rich scream, meaning that you can quickly pinch the fuel line and hear a slight jump in rpm.

Deck height..or is the question really head clearance? 2 different things. The head clearance should be as tight as possible until peak rpm drops and or glow plug life suffers.

I have tried to get more life from a P/L set by lowering the liner, now this is the only application where I have changed the deck height. Maybe someone with time on his hands has tried raising the liner, and then ran high nitro, just to see what the difference was there?