MJD

My Feedback: (1)

If a gasoline burning equivalent of a glow engine is producing more horsepower, then there are other factors at play beyond the change in fuels. Downunder nailed it with the BTU per pound versus air:fuel issue - while it is correct that gasoline has more BTU's per pound, that is only one part of the equation. The other is.. how much of it can you burn during one cycle of the engine? The answer lies in what he said - the air:fuel ratio. You have a fixed volume of air to work with, so the lower oxygen requirement of methanol allows much more to be burned completely in one cycle - the increase in the mass of fuel that can be burned is greater than the decrease in BTU's between the two fuels - shifting the advantage to methanol.

Ed.. all that gobbledy gook I wrote was referring to an exercise I went through maybe 1, maybe 2 months ago. I was curious about the relative volumes of glow fuel and air.. not the mass ratio. Whenever we're talking about 6:1, 15:1 etc, we are talking about the proportions of mass.. not volume. What I wanted to know was, how much does the change in oil percentage really affect the amount of useful fuel/air mixture the engine can intake? So I dug out the density of air, methanol, nitromethane, and castor oil, and made up a spreadsheet that illustrated the relative effect of increasing oil 5% in steps from 0% to 50% oil while maintaining a 3:1 ratio of methanol to nitromethane, on the total mass of fuel/air that was ingested per cycle. The answer turned out to be that the oil percentage has a far more negligible effect than one might think. What I figured out (and I wish someone would cross-check the math for me) was that other effects must predominate, because the net effect of that wide swing in oil % was nearly bugger all - all because the effect on volume is negligible. So I figure that other factors - viscous drag, cooling, effect on combustion, etc. are the factors at play if a measurable power loss is occurring due to increased oil %.

downunder

I did a rough guesstimate several years ago when I wondered the same thing. I guessed some figures for a 10cc engine running at 10,000revs for 10 minutes with a 300cc (10 ounce) tank using a fuel with 20% oil. Yep, these figures were chosen to make things simpler to figure out . At 20% oil, the tank contained 60cc of oil which took 10 minutes to dribble through the engine a drop at a time. The math showed that each drop of oil (on average) was .0006cc or, in round figures, 20,000 times smaller than the volume of air drawn in. OK, so an engine isn't 100% efficient so let's nit pick and say it's only 15,000 times smaller . But this 1/15,000 holds for all sizes of engines. Increasing or decreasing the % of oil in the fuel makes no discernible difference whatsoever to the volume of air the engine can draw in.

Twin_Flyer

My Feedback: (4)

Any news about this engine going into production or the availably of it?

Bill S.

hllywdb

Hi AJ,
No, I haven't tried any other fuels other than what they told me to use. I can tell you that the gas is much easier to clean up than the nitro

All good points on the fuel. Yes, gasoline and Methanol are two different fuels with different burn rates and react differently to compression, etc.. This is most likely why most attempts to simply run a nitro engine on gas give less than desireable results. As I metioned earlier in the thread, I tried running the regular nitro carb on this engine and had very dismal results. I can't offer much in the way of an engineering explanation of exactly how the fuels atomize and combust as that is not my forte, I can simply report on what results I am getting with these engines. This engine has a much different carb, it is larger, and the head is also different. With the varriouse nitro engines I have from many manufacturers, the performance ones like my Webras run a larger carb and make more power at a higher rpm. This motor seems to make more torque and is able to swing a larger prop quite happily, while at the same time turning the same prop as the nitro 40 at a higher rpm. This I would think is attributable to making good use of the differnce in the way the fuel burns.

Hi Bill, as to production, I'm guessing sometime this year.

By the way, hope everyone has a great 2013!!!!!

AJsToyz

Thank you for the updates, all very useful information. I'm not sure if you ever looked at the Fox .50 gas engine but the carb on that one looks like a glow carb from the outside. It seems most small gas engines are using a diaphragm carb such as a Walbro , or a modified diaphragm carb of some sort.

I still do not like glow plug starters but for a small plane it does beat having to fit in an ignition and power source.

Andy

hllywdb

I agree Andy,
With the available space in most 40 size planes, if I had to mount ignition, another battery and switch, plus an additional servo and switch for the required remote ignition kill, I'd just keep buying Nitro. It's the simplicity and light weight that makes this work for me.

aspeed

This seems good so far, A diesel is great for no ignition, but there are so many adjustments to complicate things, and the ether smell makes it a no go in my house.  I still like the glow, the cost is not too high for stuff under a .40, it still costs way more to drive to the field.  It will be interesting to see if this catches on.

triumphman49

My Feedback: (149)

Hi all,

Was over at the NV factory site browsing oround the forum section and found reference to the AX40 gas version. Did ask if there was any expected availibility date for this new engine. In less than an hour the "administrator" gave response that it was expected to be released this spring.

Guess another 2-3 months, at least, before they hit the market. Also referenced was - to ask any questions. Surely have enjoyed and appreciated all efforts made by HLLYWDB to keep us informed.

T-man49 in Al
Club Saito 723
Spitfire Bro 19

triumphman49

My Feedback: (149)

"The best prop is 11x6, 13000 RPM. The price will be $139.00" quote from NV administrators response

hsukaria

That's the number I was looking for, the one that starts with a $.

triumphman49

My Feedback: (149)

Hi HUSKARIA,

Pricing apppears normal for a top quality .40, which I believe it is . . . with so much more to offer. You can't get any less weight for the ignition system and cost of operation is way down. From what I've seen of NV parts, they're very competitively priced.

I'll be very interested to hear from HLLYWDB on larger prop sizes, as they would probably suit my flying style more, and help keep the noise level to a minimum. Hopefully it won't lug down the engine or create overheating problems.

T-man49 in Al
Club Saito 723

theaveng

Is that because it uses less oil in the mix?

AJsToyz

Yes, gasoline is a lubricant so it needs less oil then alcohol based fuels. We do not know the mix yet but guessing its between 20:1 and 32:1.

theaveng

So that's 5%. About 1/3rd as much as glowfuel's oil.

Gasoline is a lubricant? Hmmm. Even now that they've removed the sulfur from the gas? I'm surprised this engine does not experience knocking (preignition).

hllywdb

Hi T-man,
I almost made it out to the field on Thurs, but rain and wind set in. On the next trip I will be trying some 12 and 13" props. At this point I don't even bother testing them unless it is in the air as bench tests reveal very little about how an engine actually performs with a given prop.

As far as pre-ignition, I haven't gotten any yet. That's something I expect more with glow fuel when you load up a big prop without any head shims. Same with overheating.

Bill

triumphman49

My Feedback: (149)

Hey hllywdb,

Ahh for Mother Nature, Was wondering about different ehaust that might be available for the little NV. Can you advise bolt spacing and size so can be looking around?

Let us know when you can how she handles the bigger props, . . . . and Thanx again.

T-man49 in Al
Mike Brennan

hsukaria

$140 is quite reasonable for what is being advertised. I have the glow AX-40, and have purchased parts from NV Engines already with good results.

hllywdb

Ok,
I got a chance to try a couple more props today. 1st I tried an APC 13 X 3.75W, which is a good 3D prop for a 65. As I expected, it runs it, but just less than 10,000. No surprise as this one is too much for my 55AX with a performance muffler. But it didn't complain and was well behaved.

Next up, I ran an APC 12.25 X 3.75 wide 3D prop. This was giving me about 12,000 on the ground without leaning it out too much, I was worried about it unloading and getting lean in flight. Again the engine had no complaints. 3D is not my forte and I am flying this in a sport plane, but it would hover and pull up from a hover with this prop. Also to be noted is that it hard to make a bad landing with a 3.75 pitch prop.

I then made a couple more flights with the APC 10X7 and 11X6 respectivley. The 10X7 flies the plane super and the motor runs great with no hesitation or burps. With the 11X6 it just runs as smooth as an electric and behaves as nice as the Queen having afternoon tea. The 11X6 is THE prop for this motor. I am thinking of trying a MAS 12X5 next, as I have a suspicion that may have the motor right in it's happy zone as well.

Bill

fiery

My Feedback: (2)

Thanks for those figures. It is nice when a product is properly "field tested" before being released.

Looking good ..

triumphman49

My Feedback: (149)

Hi Bill,

Glad Mother Nature co-operated, and thanx for testing those props. Hope your rite-on about the happy zone with the 12x5 size as I believe the spped would be just about rite for a good size Cub or mabey a TigerMoth or such.

With an 11x6, I believe it would even fly a 4*60 with good authority. How was the idle with that 12.25 prop? Under 2 grand I suspect. Did you have a chance to check the exhaust bolt spacing?

Do you know if there are any U.S. distributors or will purchase just be from the NV web site?

Great to hear from you

T-man49 in Al

hsukaria

I am installing my glow AX-40 on a Hangar 9 Sundowner 36. It calls for a 9x7 or 9x6 prop. Would that be too small for the gas version?

AJsToyz

Sounds like may be a 9x9 or 9x8

hllywdb

On the 40AX glow, the 9X7 or 9X8 is fine. Those engines will scream and LIKE it. As for mufflers, I know of none that are made for the bolt spacing (same as the nitro 40). That being said, I have done some experimenting on the nitro 40 and find it responds almost identical to the OS 46 and 55 with a tower/GMS/Jett muffler. I used a doner muffler from a GMS 32 that got damaged in an unscheduled landing. I used the center tube (between the front and end cap of the muffler) did some crude machining and used a longer bolt. Added about 1.2" in length. Presto! Instant 1000 rpm for free. No issues with draw or hesitation either. Would be great if Jett started making one for the 40/46 NV.

Bill

hsukaria

I found an old muffler at a swap meet that claimed to fit an old OS 40 FSR. The bolts are just a bit wider than the AX-40 spacing. With some drilling, I was able to install it.

It would be nice if MAC and JETT did one without the need of an adapter. But I am willing to use an adapter too.

triumphman49

My Feedback: (149)

Huskaria,

Did find a Norvell AX40 shown on MACS site - 2800 series with 32.21mm \ 1.268" bolt spacing (3.5mm x 12mm cap screws).

Also shows a 6300 bolt thru (looks like sized to 5-40sz screws), one piece muffler with 32.11mm \ 1.264" spacing. Shows as a 25 size -Does exhaust volumn remain the same gas vs glow?

T-man49 in Al