Author Topic: OS 46VF on a Muffler? (Read 2391 times)

Peter Nevai · « **on:** January 02, 2018, 08:16:27 PM »

Hello There, Has anyone used a OS 46VF on a muffler setup or is it strictly a tuned pipe engine. If used with a muffler what was the thing that worked for you (Prop, Tank, etc.) I am thinking of putting one in a SIG Magnum which is not designed for a tuned pipe.

Dennis Toth · « **Reply #1 on:** January 03, 2018, 01:43:09 PM »

Peter,
I have used the OS VF 40 & 46 in the Sig Magnum both were on pipe. For the pipe you need to add the pipe tunnel to the bottom, worked OK. I have thought of use one of Randy's header mufflers which would save at least 1/2 - 3/4 oz off the pipe. I think you would run a failly low pitch (3.75" or maybe lower) to be in the proper rpm (guess 11 -12K range?) control range for the unpiped VF's. Maybe Brett can comment on the applicable rpm range. One thing you might consider for the Magnum is to increase the tail moument to around 17 1/2" hinge to hinge and increase the elevator/stab area to 22 -24% of the wing area. This allows a little bit more reward CG location and helps the corners. I did this on mine and liked the way it flew.

Best, DennisT

Brian Hampton · « **Reply #2 on:** January 04, 2018, 05:27:40 PM »

To answer the original question, I see no reason why there'd be anything wrong using a muffler on a VF. The VF 40/46 port timings are very mild and virtually identical to other engines that are run with mufflers such as the Brodak B40, ST G51 stunt, Enya 60-IIIB.

Brett Buck · « **Reply #3 on:** January 04, 2018, 07:23:13 PM »

Quote from: Dennis Toth on January 03, 2018, 01:43:09 PM

I think you would run a failly low pitch (3.75" or maybe lower) to be in the proper rpm (guess 11 -12K range?) control range for the unpiped VF's. Maybe Brett can comment on the applicable rpm range.

I have very little idea, maybe start with a 11.5-4.5 Eather 3-blade. It will probably "work" to some degree if you get the prop right. See what happens in the air with that and about a .270 venturi, and play off the venturi size, prop pitch, and rpm off until you get something that will operate in a stable medium 2-stroke. If everything is OK in level flight, but weak in the maneuvers, adjust the pitch at the last few stations to add 1/4" -1/2". You've gone too far if you feel it suddenly "leap" around corners.

DO NOT grind on anything, do not add head gaskets, do not shim the liner, and do not block any ports. That way, when you give up and run it with a pipe, you won't have destroyed anything important.

I can't see why you would want to run it on a muffler. With a pipe, we know exactly what to do to make that work and it's far simpler than trying to develop something from virtual scratch, and is guaranteed to perform better and be more consistent than on a muffler

No pipe and you're really making it a complicated problem, experimenting with something for which there is *no* base of information.

Brett

Air Ministry . · « **Reply #4 on:** January 04, 2018, 08:13:33 PM »

Thinking many have run the VF 40 unpiped succesfully / so should be ok ,

Theyve similar port timing to a FSR 45 . But with bigger crank - passage - and late closing there . but wtf - give it a go .
A 45 FSR bitza is very authoritive on a 12 x 4 bolly 3 blade , in a Magnum winged thing .

A x-45 ST has very similar timing . (

Hello Brett .

( but mines lower at 140 Ex rather than the OS's 145 ( and Chinns ) ) .unmodded .

Muffler could make a huge differance . A tooned pipe header , plugged & with a series of holes aft - like a tounge muffler might be ok.
Turkey here runs a unmodded side rear header on a ST 60 with a rubber RC angle thing bunginging the rear , dropping the Gunge clear .

If this dosnt work you can always take to the underside with a disc grinder .

Air Ministry . · « **Reply #5 on:** January 04, 2018, 08:26:38 PM »

Cor Blummy , looking for a picture of a good perforated Brooklands Can. . THE pOMS HAD NOISE REGULATIONS THERE PRE WAR ( yea , That War )
Brough Superiors , Velo's & J.A.P.'s . But as we found a picture of the renouned Grindley Peerless $:-\$ multitudinously drilled . . .

A similar effort ( the Muffler assy ) might be worth a try .

On a Straight Tube , however , multiple outlets at multiple distances would generally be though to provide a wider power band / broader tourque curve .
Hence ones dozen 2 mm holes , maybe two rows over 1 1/2 inches .

Theoreticaklly , a crayon line down your header - should burn off at wave points first . Furthest Aft ( due to multiples ) should be ' tooned length '
for something ,

Likely varies with R P M . Assume choosing RPM before observing burn might be the best bet .

Been meaning to drill my header for the Irvine 40 & K&B 7.5 thus , for the S6B.

Steve Helmick · « **Reply #6 on:** January 05, 2018, 12:07:41 AM »

I'm with Brett, because most folks could wear out an airplane before they got the power system sorted. MUCH better to stick with mainstream power systems.

I've been running the .46VF for awhile, and pay attention when some info comes upon me, and ask questions when I can. I know they were originally intended for R/C Pattern, and that they didn't come with a muffler. That implies that they were intended to use tuned pipes, even ignoring the rear exhaust. I'm pretty sure that's the case, anyway. I'd suggest a morning telecon with Randy Aero about it. If anybody has tried it, I'd guess he would know about it or has done it himself. He's working on a batch of CF pipes, so should get in the system soon...get on the list. Many folks modified existing models to include a pipe tunnel or just left it hanging out a bit. Fact is that most pipes hang out about 1/3 or 1/4 way anyhow, and nobody seems to mind or give a hit for the AP's. It's got to run cool, or it won't run well.

Steve

Air Ministry . · « **Reply #7 on:** January 05, 2018, 08:52:01 PM »

forget the bottom rubbish .

One of them & one of those . K&B 6.5 & 7.5 SR II , X 45 & OS VF all have same blot pattern .

If THAT dosnt work , try the bag pipes . The VF is actually more conservative cylinder port timing than the FSR magnum , at least .

unless some turkeys dropped the VRP pylon sleeve in it , the VR 25s are two differant set ups , the DF being ' race timed ' so be wary there .

http://sceptreflight.net/Model%20Engine%20Tests/OS%2040VF%20and%2046VF.html

Mecoa Ones .

Brian Hampton · « **Reply #8 on:** January 06, 2018, 07:08:07 PM »

Quote from: Matt Spencer on January 05, 2018, 08:52:01 PM

http://sceptreflight.net/Model%20Engine%20Tests/OS%2040VF%20and%2046VF.html

It's better to use this .com site http://sceptreflight.com/Model%20Engine%20Tests/Index.html because I haven't been able to update the .net site for a couple of years. I haven't counted but there's probably a couple of hundred extra tests at the .com site.

Peter Nevai · « **Reply #9 on:** January 12, 2018, 09:47:33 PM »

Thanks for the suggestions, I read somewhere that someone shoehorned a RO-Jett 65 with a pipe in a sig magnum. I wonder how they worked out the pipe mounting as the fuse is not deep enough for a tunnel but too deep for the pipe to be outside of the fuse all together. I will have to build it and see how I can make the VF work with a pipe, maybe there is a Header with a greater drop than the one I have. The prop I have mounted is a Majic Carbon prop from Randy 12 X 4.33, not certain of the Venturi diameter though. And no I am not modifying the engine in any way. I have ABC liner and piston kit from Randy as spares, which reminds me I have to get the sleeve & piston back to Randy because I got one of the ones that did not have the piston skirt cut.
Otherwise I will need to find another engine to put in there. Unfortunately there are not many around that are worthwhile to mount. Many of the Ebay motors are looking pretty raggy these days else they want ridiculous prices for them.

Peter Nevai · « **Reply #10 on:** January 12, 2018, 10:08:32 PM »

Quote from: Steve Helmick on January 05, 2018, 12:07:41 AM

I'm with Brett, because most folks could wear out an airplane before they got the power system sorted. MUCH better to stick with mainstream power systems.

I've been running the .46VF for awhile, and pay attention when some info comes upon me, and ask questions when I can. I know they were originally intended for R/C Pattern, and that they didn't come with a muffler. That implies that they were intended to use tuned pipes, even ignoring the rear exhaust. I'm pretty sure that's the case, anyway. I'd suggest a morning telecon with Randy Aero about it. If anybody has tried it, I'd guess he would know about it or has done it himself. He's working on a batch of CF pipes, so should get in the system soon...get on the list. Many folks modified existing models to include a pipe tunnel or just left it hanging out a bit. Fact is that most pipes hang out about 1/3 or 1/4 way anyhow, and nobody seems to mind or give a hit for the AP's. It's got to run cool, or it won't run well. Steve

I actually don't mind if the pipe hangs completely under the fuse. I just don't like taking the structural integrity away from the fuse under the wing by cutting away so much of the bottom plank. I suppose I can extend the sides a bit part way to make a sort of semi length tunnel just to make it pretty. My biggest concern is structural integrity without piling on a ton of weight.

Brett Buck · « **Reply #11 on:** January 12, 2018, 10:37:38 PM »

Quote from: Peter Nevai on January 12, 2018, 10:08:32 PM

I actually don't mind if the pipe hangs completely under the fuse. I just don't like taking the structural integrity away from the fuse under the wing by cutting away so much of the bottom plank. I suppose I can extend the sides a bit part way to make a sort of semi length tunnel just to make it pretty. My biggest concern is structural integrity without piling on a ton of weight.

Mold an upper half of a tunnel, cut away the bottom and fit the formers to the outside of the molded tunnel, use it to replace the fuse bottom, and it's as good as it was originally. That's what everybody did when we first converted piped airplanes. I did it in a couple of days, flew the same airplane with an ST46 one weekend, and a 40VF the next weekend. Took about 1/4 lap to realize I was done with 4-2 break engines.

Brett

Peter Nevai · « **Reply #12 on:** January 13, 2018, 05:23:22 PM »

Quote from: Brett Buck on January 12, 2018, 10:37:38 PM

Mold an upper half of a tunnel, cut away the bottom and fit the formers to the outside of the molded tunnel, use it to replace the fuse bottom, and it's as good as it was originally. That's what everybody did when we first converted piped airplanes. I did it in a couple of days, flew the same airplane with an ST46 one weekend, and a 40VF the next weekend. Took about 1/4 lap to realize I was done with 4-2 break engines.

Brett

Sounds like a plan Brett. Back in the day, 4-2-4 was ow everyone ran their cast iron engines, that's all there was. With the proliferation of schnurle ported engines with more radical timing it is best to run them in a manner that they were designed for.

Author Topic: OS 46VF on a Muffler? (Read 2391 times)

Peter Nevai

OS 46VF on a Muffler?

Dennis Toth

Re: OS 46VF on a Muffler?

Brian Hampton

Re: OS 46VF on a Muffler?

Brett Buck

Re: OS 46VF on a Muffler?

Air Ministry .

Re: OS 46VF on a Muffler?

Air Ministry .

Re: OS 46VF on a Muffler?

Steve Helmick

Re: OS 46VF on a Muffler?

Air Ministry .

Re: OS 46VF on a Muffler?

Brian Hampton

Re: OS 46VF on a Muffler?

Peter Nevai

Re: OS 46VF on a Muffler?

Peter Nevai

Re: OS 46VF on a Muffler?

Brett Buck

Re: OS 46VF on a Muffler?

Peter Nevai

Re: OS 46VF on a Muffler?