Charley

My Feedback: (2)

Have you received your engine back?

You never did tell me the address you shipped your engine to or the contact person. I'd send mine all the way to Russia in order to find out why I can't get it to run for over 3 minutes.

CR

hsukaria

They probably took it with them to Syria or the Ukraine. It will come back when peace breaks out in the Middle East.

Charley

My Feedback: (2)

I emailed CS about sending mine back to Russia. They're giving me the runaround. Not forthcoming with an address or contact person.

CR

hsukaria

I (and several other guys) had a similar experience with the Mintor engines. Mine was gone for 9 months and never heard back from the factory in Italy. But it showed up in the mail one day and it was fixed right. So you never know. But at least with the Mintors, there was a local distributor who coordinated the whole effort. Hopefully NV Engines will stick to their word. I still have not repaired mine and if I do, I will convert it to glow.

Charley

My Feedback: (2)

I sent my GX-40 to NV Engines in CA, care of "Dmitry." He sent it on to the factory in Russia. I just had a Email from Dmitry saying that they ran my engine in Russia and found nothing wrong with it but installed a new HS needle "just in case." They suggest outside causes for its not running right for me, including mis-tuning, fuel tank issues and taking off the "glow ignitor" too soon. I wrote back; told Dmitry I wouldn't argue causes as long as the engine would run through a tank of fuel after I get it back. Anyway they will send it back to CA. Dmitry will let me know when it arrives.

More later,

CR

hsukaria

I purchased a new crankshaft, glow head button, and head shims. I will be converting mine to glow. I have had my AX-40 for years now without a single glitch. Hopefully, this engine will behave as glow.

Charley

My Feedback: (2)

If it runs better on glow, I'd be scratching my head as to why. Didn't yours break the crankpin off?

I bent the rod on mine due to a hydraulic lock and an electric starter. The engine has never run right since I replaced the rod. I did wonder if the crank was twisted or the crankpin might have been knocked out of alignment. That's one reason I sent it back to Russia. The factory claims it runs OK. Gawd, I sure wish I could have asked them if they ran it for 10 minutes or more. They say the replaced the HS needle JIC. all I can say is if it runs through a tank of gas after I get it back, that must be on magic HS needle!

CR

hsukaria

Yep, broke the crankpin. I blamed:
a. The higher compression load on the crankpin.
b. I got it from another guy who messed with it.
c. Later on, I realized that the crankcase backplate was loose, maybe the previous owner loosened it and didn't tighten it back enough or the vibes from the engine loosened it.

So, now I purchased a new crankshaft and the glow headbutton. I have it all assembled and will bench run it in a few days.

I would say to everyone dealing with the GX-40 to check the backplate to make sure it is not loose.

the pope

Hi there Husky , Ive got a sneaky suspicion that when mine ate its crankpin the backplate was also loose . They do have serious compression and I was very carefull so I cant say that I put unreasonable force on mine . If the guy ran it then that was probably enough to cause probs. I remember as soon as I ran it lean enough to have smooth running all hell broke loose . I dont think Ill spend more $ after bad on this thing , a shame really . I think they just did the bare minimum to convert it from glow to gass . Cheers

hsukaria

Hi the pope,
That is exactly when mine croaked, when it was getting broken in enough for me to lean the low end needle a tiny bit so that it would idle and land with power. Up until that point, all my landings were deadstick. But I am now going to run it as glow, not gas and avoid stressing it so much. I have owned a glow AX-40 for at least 8 years with great results. Less power than the GX-40, but it has performed well so far.

the pope

With mine it was reliable in regards to dead sticks but I had it so if I went 1 click richer it would have stopped .

Charley

My Feedback: (2)

Dammitt guys,

I've run glow engines in RC models for years & use the condition of when I go nose up and the engine noticeably leans out, it's time to land. Always had time to make a landing and taxi it back to the pilot station with a bit of fuel in the tank to spare. If you're describing the engine dying before the tank is dry that just isn't normal.

CR

hsukaria

Sorry for the late reply Charley, but in my case, I had to run it so rich that it would not idle for long enough to last the duration of the landing approach. As time went on, the engine would idle longer into the landing approach. By the time I got it to idle long enough to land without quitting, the crankpin died.

The more I think about it, I think that there is greater loads on the crankpin due to greater combustion pressure. But not sure if that is the only reason. Both my engine and the pope's had a loose backplate when the crankpins broke. But not sure what happened first.

I wonder if these engines could benefit from first being fully broken in as regular glow engines and then converting them to gas, making it easier to tune. I now have 2 GX-40s converted back to AX-40 by replacing the broken crankshafts and the headbuttons. I also added the copper head shims for glow. One of them I ran it on the bench and it did quite well. I will be testing the other converted engine soon. Should be no trouble.

I intend to convert at least one of my 3 AX-40s back to gas someday, but I will also use a Walbro pump/regulator to help with the fuel management to ensure no lean runs happen.

aspeed

Just a thought on broken crankpins. I have had a few go on me, and believe it is because of too little clearance on the rod to crank fit. When it gets hot, it seizes and snaps it off. I believe .002" clearance is about right which really seems quite loose. Many cranks I have had on some higher performance motors had scoring on the crankpin, or were blue. Maybe a lapping or at least a good break in would help. Just a thought, YRMV.

hsukaria

That's why I was thinking of breaking them in gently as glow engines with extra castor oil, then transitioning to gas. At least tuning will be easier since the engine is fully broken-in and stresses on the crankpin will be lower.

Sport_Pilot

Most rods in auto engines are thrown due to oil starvation, so I totally buy that. I threw a rod once because of a spun bearing.

slkret123

Hi. I hope some of the NV GX40 users are still monitoring this thread. I know this engine has been out for a while but I just discovered it. I'm building a control line model conversion to R/C and am looking for an interesting engine to put in it. The GX40 is certainly that. I've fully read the long forum threads and am a little concerned that the engine is finicky to run. I read stories about blown head gaskets, bent rods, very sensitive needle valve settings, special tools and very hot running. I also read about the special steps necessary to mix the Klotz oil in gas and with the high amount of oil it's nearly as messy as a conventional glow engine.

All that said is the only attraction here that it is more powerful than a conventional .40 size "nitro" glow engine and the fuel is a little cheaper? I'd really like to put an unconventional engine in my unconventional plane.....but not if it is a pita to operate. I'm hoping to get some feedback from guys who have been running these engines for a while.

Steve

Sport_Pilot

I don't think the numbers posted were more powerful as glow. But a lot better than you would expect. Gas usually has less than 80 percent of the power of glow. Less if compared to a high nitro glow engine.

hsukaria

Hi Steve,
I was hoping that this thread would be revived. I have been able to overcome all the obstacles that you mention except the one that I encountered and also another member here encountered ("the pope"). We both had the crankpin shear off the crank inexplicably. I think that the extra load on the crankpin from the higher pressure of gas combustion must have stressed the crankpin beyond the design limit.

I contacted NV Engines regarding that issue and they said to add an extra copper headshim. That means that the engine should have 2 copper headshims and 1 asbestos gasket. I plan on trying this out someday in the near future since the benefits are worth the effort IMO.

The issue with finicky tuning is something that can be learned. If you are used to running glow engines on low nitro, this won't be a problem for you.

The leaky head gasket is resolved by making sure that the head is screwed down real tight. I had that problem at first and fixed it by running the engine a little at a time and tightening the head and head screws while the engine was hot and re-running it until the leak was gone.

The bent rod happens because the engine has to run extra rich during break-in (which is fairly long compared to OS) and people slam the engine starter on it while the engine is hydro-locked. You can avoid this problem by checking for hydro-lock before every start attempt. For that reason, I don't recommend inverted mounting and making sure the fuel tank level is very near the level of the carb.

The oil slime from exhaust is nasty looking black color. But, it cleans off real easy because the gas disolves the castor easily. You can clean the model with a rag after every flight without having to use any cleaner. No big deal!!

So for me, the only issue is the crankpin. As far as I know, only two of us have experienced that failure. With the extra headshim, there will be loss of power, but hopefully no failures. Also, having the extra headshim might bring the power back down to the level of a 40 rather than a 46. That is fine by me as long as it holds up.

In retrospect, I think that breaking in these engines with nitro-glow fuel first and then switching them to gasoline would help a lot, IMHO. But that would mean that you need to purchase the nitro-glow head button for break-in. Something to think about.

I hope that helps. Keep us up to date in what happens.

AndyW

My Feedback: (1)

I may be someone who has worked with Norvel engines more than anyone, concerning running them with exotic fuels, notably diesel, biodiesel and all manner of oils. The Norvel lends itself to do this because of it's unique design. I have yet to try to run them on gasoline, but I'll do that in the spring with a unique Norvel .15 on which I;ve installed a variable compression head that utilizes a glow plug.

Before even considering such work, the first thing that I did was to install a heavy duty rod. All the Norvels can benefit from this, in my opinion, the rods supplied from the factory are just on the edge of being adequate. There are rods out there that are drop in replacements from other engine makers. I have a list somewhere, I'll try and find it. Those rods are all brass or bronze bushed. Always nice to have in a rod.

As far as crankpins, I have hammered Norvels with starters even when run as diesels, hot and cold and only once in 13 years did I have a pin break.

When it looked like Norvel was going to go away and never come back, I bought out all their returned engines. Clearly, many were abused. But more than one, (out of 25 of all sizes) had broken crankpins and bent rods that were in perfect condition.

I've not yet run a Norvel on gasoline but I plan to do that in the spring using a unique .15 on which I can vary the compression on the fly. I wouldn't venture to do that with a stock rod. All the Norvels, .15 and up have stronger rods available from other engine makers. These are a drop in replacement and have bushed ends. In my opinion, stock, Norvel rods are just on the adequate side of things.

I suspect that some cranks are just not heatreated correctly,,, brittle. I say this because while I'VE been lucky with pins, (only one, broken on the bench) I've had more than a few prop studs snap when putting on a prop. This even happened once, a few minutes after the prop was secured.. POW, like a rifle shot,,, had to look for all the bits. It's apparent that Norvel makes everything on their engines, even the studs, so this may be the problem. Just my observation.

My opinion? Fun to experiment with but if you want to bolt on a good engine, which the Norvel IS, just run it as glow and have fun with your plane. When you get a replacement engine, some day for that plane, go ahead and stick the Norvel to the bench and get out the gas can.

hsukaria

I am very interested in conrod replacements. As far as crankpins shearing, I am hoping that mine was just a fluke due to manufacturing errors. There is no other reason other than excessive loads on it from the higher gasoline combustion pressure. The solution has been given by NV Engines to add an extra headshim not only for this issue, but for other problems that other users had been having.

By the way, the head button for the glow version is the typical conical shape for nitro-glow engines, but the head button for the gas version is just a flat surface to increase the compression considerably. So, if somebody wants to run the engine in either fuel, they can purchase the gas version and also a nitro-glow headbutton as a spare and then switching between fuel types would be very easy.

Besides that, I have been running the nitro-glow AX-40 for 8 years now with no problems, That engine has been reliable and dependable and also easy to use. I also recently acquired a used 15 BigMig (bushed) and a NIB 15 AME (BB). I bench ran both and I must say that they are quite impressive. The old bushing version has the older single needle carb without any adjustment for idle. I was concerned at first about idle stability, but after bench running it I have no concerns about that and am happy to only have to fiddle with only one needle. I was able to get 15,500 RPMs on a 8x4 prop with 15% nitro fuel. That is impressive for a general sport engine IMHO. I plan to install that engine on a Sig Wonder for some serious fun.

aspeed

It would be my guess that control line would be ideal for this motor. No idle or midrange problems. As long as it is not over compressed it should make lots of power with no engine damage. Most stunt type motors are detuned anyway, so power would not be an issue, and the glow Norvel performed better than a lot of other similar sized motors anyway, the the gasoline loss would pretty much even things out. Oh, and Andy, try a bigger carb on one of your .15 Norvels with no muffler, and get ready for a surprise.

hsukaria

Your statement confirms what I had been experiencing using the gas engine. I had been running it extra rich for break-in at the expense of idle performance. As the engine break-in progressed, I would lean the engine a little bit at a time to improve idling. If the engine doesn't have to idle like in control line use, the user doesn't have to worry about throttling and idle issues while in break-in.

AndyW

My Feedback: (1)

I've run all the Norvels on diesel and have not had more than one break a pin. Diesels require much more compression than glow but perhaps not as much as gasoline. I'll look for that list of rod replacements and get back to you.

AndyW

My Feedback: (1)

Thanks for that tip, in fact, the Norvel .25 carb is a drop in replacement. Lots to do come spring.