I've been hearing stories of hands getting whacked by propellers while adjusting the high-speed needle, and am wondering what the frequency of such accidents is.

Have you gotten bit?

I have never been wacked by a prop while adjusting the HSN but your hand is still dangerously close to the blade. I have, in my earlier days, adjusted the LSN and got my finger wacked at idle. Thats when I learned to kill the engine when adjusting the LSN.

A lot of engines (if not most) have the low speed needle right up there near the prop arc. Not a good place to be putting fingers while the engine is running.

The OS AX series of engines have an angled high speed needle, angled back with a length of very stiff wire to go into a hole with a set screw in the needle valve knurled body, and a little knurled thumb dial that mounts on the wire. This puts the high speed needle adjuster back further and away from the prop arc making that a safe and secure method of doing the high speed mixture adjustment.

CGr

Personally, I don't care for remote needle valves. I've only been bit by a prop once, it was when I was a teenager and I was NOT adjusting a needle valve at the time. Like CGR said, the new OS engines have the HSN slanted back and I think that's the best method. The next best thing is to keep in mind at all times hat your fingers are dangerously close to that spinning prop!

Never reach around an engine.

Walk around to the back side of the prop and approach the HSN slowly and carefully from the rear - And again, remember where the prop and your fingers are!

I like the remote needle valve myself. I've never had a prop strike ( knock wood) and I like anything that keeps my fat fingers away from a piece of plastic spinning at 11,000 + rpm.

To me over the years since the inception of remote needles it has become apparent to me that the needle valve location has very little to do with the number of physical propellor incursions. Actually argueably a remote needle may aggravate carelessness around a propellor.

Most physical incursions seems to be caused by carelessness doing other things around a running engine.

As far as whether or not I like remote needles is kind of pointless since the majority of manufactures seem to have embraced them. I do like the needles used by TT on most of their engines that are angled rearward by twenty degrees or so.

John

I like the remote NV.

BTW, only the larger AX series engines have the angled valve. The 46, for instance, doesn't.

I've never had a serious prop/finger colocation , but I've had my nuckle buzzed by a Norvel .061 turning 21Krpm a couple times. The NV on this engine is about half an inch behind the prop. Not even a broken piece of skin, but wakes you up anyway.

The idle is best set with the engine stopped, in small increments. You can't really set the idle by ear like the HS needle anyway, as the changes take too long to take effect at idle. Run, evaluate, shutdown, adjust, run, evaluate, wash, rinse, repeat....

J

The only time I've had problems with them was with a .25LA I've had on a couple of SPADs. The plastic backplate/needle valve holder kept breaking during minor crashes/hard landings and I'd have to spend $6 on a new one. I have since stopped crashing with that particular engine and haven't had to use the three spare backplates I bought.

I do get pretty nervous adjusting the high speed needle on my Super Tigres. They are very close to the prop. I agree that the angled HSN on the new AX is the best solution.

I have never hit my fingers. It is a bit scary getting them as close as some engines require but so far no problem.
My theory is, if you do touch the prop while adjusting the needle it probably won't do alot of damage because you will be hitting the back of the prop which will, because of its angle, try to push your fingers away. That's my theory anyway but I sure don't plan on testing it [X(]

The remote needle valves, as on the older OS engines, are ok until they break. Then you're stuck without and engine until you can replace it. The plastic housing breaks (and I've had that happen just both from a hard landing and one just broke off at the mounting screw).

IMO, the angled one as on the OS AX series is the best method system.

CGr

Here are a couple of pictures to show the difference.
The first picture is an older OS 40FP with a strait valve, the second is an OS 46AX with remote. And angled valve will be a bit better than the strait one.

I prefer the remote valves as long as they are not otherwise problematic.

They make it easy to adjust a running engine.

I will not ( nor should not ) attempt to adjust an engine with a carb mounted needle close to the prop, so I've never been hit by a prop while adjusting an engine.

Unfortunately I have tested Missleman's theory...

I have been hit by a prop, when attempting to pick up a running pusher plane ( Bobcat .52 ) which did permanent nerve damage.

The prop did not push my fingers away. It sliced the tips of three fingers on my left hand 1/4" under the nail, following the curve of the finger tip, the middle finger was sliced down to the bone which finally caused the engine to stop.

While it has healed I have no sensation on the tip of the finger, nor the finger tip "pad".

I can attest that the prop WILL do a lot of damage.

This may be different than the "slice and dice" damage caused by the prop tips, but it is both painful and severe.

My god that's close!!! Just the pic of the remote needle is calming my nerves, and I haven't even seen it up close!

Hmm...[sm=confused.gif]

adjusting the low side to me can be most dangerous if you do it while the engine is running using a screw driver. I have seen several propellers shatter, this happened to me once and I learned my lesson. I was lucky the propeller was all that got damaged. most people don’t wear safety glasses when working around a running engine. I was a mechanic all my life and have had my eyesight saved several times thanks to wearing safety glasses. we all have made dumb mistakes at one time or other. I like the remote high end screws, but like anything caution and common sense is always needed.

Well, that's it. I totally have the OPTION of having to put my hands dangerously close to something that can PERMANENTLY damage them for the rest of my life. Why the hell would I do such a thing on my first glow engine???

Thanks guys[sm=bananahead.gif]

Just bought an OS 46AX

Now I can get back to my life[8D]

Thanks everyone.

In order of preference...

1) Angled needle valve such as the OS AX series (fewer parts/gaskets/seals to cause problems)
2) Remote needle valve (safer than a straight valve but more parts as described above)
3) Straight needle valve (works as well as the angled but you must be more cautious)

I have been bit by a prop once and it was not while trying to adjust the needle valve.

The 46AX from tower doesn't have the angled valve; it has a remote valve mounted on a bracket instead of the back plate. Can be rotated 90 degrees. Larger AX's have the angled valve; maybe there's a carb replacement for the 46 if you really want the angled needle. I do think the angled valve makes the most sense, and from my completely inexperienced, yet mechanically amoured background, and would be ideal.

The pictures of misselman posted...that's a NO, NO of an angle to be puting your fingers/hand when adjusting
a needle valve.

Adjust it from the BACK, NOT the SIDE. Meaning stand on your wing if you have to.
It will obviousely prevent you from reaching over to prop, if you're standing behind the engine.

I just don't understand..how people can still want to stand in front of the prop and reach over.

if anyone is stupid enough to adjust the LSN while the engine is running...i don't know what to tell them.
I mean...if you have a super long miniture flathead screwdriver , it would be possiable.
But how precise can you tune it when the engine is vibrating anyway.

I mean you spent hours and hours bulding or putting a model togehter...even an ARF...then you're going get in a hurry
when it comes to your hands or fingers.

FatOrangeKat

I was clearly mistaken. I was under the impression that all OS AX series engines had the angled needle valve. Not so with the .46. However, it does have the remote needle valve assembly, so your fingers are safer than they would be with the closer needle valve assembly as with other engines (including OS).

However, I am certain that you will have great performance out of this engine. Also, just be careful with handling of the engine. That needle valve assembly is made of plastic or phenolic or some such material and can.. and will.. break if not handled carefully.

The good news is that the assembly is available as a replacement part.

Tighten the little screws that hold the assembly onto the metal mounting plate, but do so carefully. Don't 'overtighten' it. Make sure it's snug and leave it alone. Perhaps a drop of 5 minute epoxy on the ends.. THE ENDS of the screws may help keep it in place. Rotate it as you need to after you decide where the engine is going to go and where you want the needle valve to point towards, and then secure it in place.

As I said, you will enjoy this engine. It is powerful as well as quiet, start well and easily, and very easy to maintain. Get some after run oil.. marvel mystery oil, or even Mobile 1 synthetic oil, and put 5 or 6 drops in the engine after the days flying, and after you drain the tank and run the engine dry of fuel. This will keep things lubricated and free of moisture.

Let us know how this works out for you.


CGr.

So almost 2:1 in favor of the remote valve; this is probably the most 1 sided discussion I've seen so far, and its still a crap shoot! After run motor oil? Voltwatch? Magnum/Supertigre? castor oil? Is there a topic that's not highly debated? Let me know, I'll debate it!

Thanks guys, I wanted to be 'different' with a Super Tigre; I wanted to tame the beast. But I feel some kind of serenity with the purchase of the OS 46AX - confident at least.

FOK one thing you will notice is the 46 AX comes with the #3 plug in the box, I did my break in with that plug and it worked fine.
one thing I found is the engine ran a little better using a #8 plug after break in, and has a smoother idle as well.
the #3 tended to burn out faster even after the break in was done, so I switched plugs and it seems to run better could be just mine but the #8's are a little more expensive by a couple of bucks is all.
when breaking in engines plugs tend to burn out faster untill the engine is fully seated, the metal shavings can foul the plugs rather quickly so don't be surprised when yours does as well.
read your manual and follow the simple break in procedure and you will have a great running engine for a long time to come, mine is a great little powerhouse.
I like the remote needle on all of my planes that have them, there doesn't seem to be any perceptable performance difference, and when your fingers are further away from the prop the better off you will be.

I've broken every types of rear needle valve brackets wheather they're metal or plastic.
The LA's metal bracket being not so thick will vibrate a bit more..but it didn't effect the engine.
I actaully like the way OS designed it becuase i can rotate the needle assembly to have the
needle's head pionting up instead of stick out on the side.

The only thing i don't like about them is sometimes there's not enough room behind the engine,
depending on a model. And when I mount the engine side way the fuel tubbing has to do wierd
bends.

Generally i can refuel through the intake line if it's a regular needle valve.
If it's a real needle..and not wanting to mess the tubbing, I refuel through the muffuler's line.
I just have to crank harder.lol Sometimes I flood my enigne.

This arraingement works quite nicely, simple and reliable whenever the clunk to needle line is difficult to get to. The slightly longer line does not present any running problems.

John

1. I would have been well clear of the side of the prop and, in fact, would have been behind the wing as much as I could get with the airplane sitting on my bed trying to take a picture of the needle. Look again, I have my left hand on the needle so the rest my body is well clear of the prop arc and am clearly standing behind the prop, not in front as you suggest.
2. I was only showing the difference between a remote needle and a strait needle at the OPs request via a PM
3. I was also holding a camera in my right hand and trying to get a good angle on the needle for the pic.