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OS 46 VF versas OS 46 VR DF

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Old 07-12-2004, 07:17 PM
  #1
iflyj3
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Default OS 46 VF versas OS 46 VR DF

I have an OS 46 VF which has a front carburator and rear exhaust. I also have an OS 46 VR DF which has a rear carburator and rear exhaust. They both have the same case as it is marked with a V. The only difference I see is where the carburator is mounted. My question is; Given the same size prop will they perform the same? I am trying to decide which one would be the best on the plane called the Vertigo.
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Old 07-12-2004, 07:21 PM
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Default RE: OS 46 VF versas OS 46 VR DF

The VRDF is a fan engine... it has to be piped and turns 22,000+ rpm ideally...

I don't know what kind of plane that Vertigo is, but unless you intend to do 180 mph with it, go with the VF engine....
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Old 07-12-2004, 07:25 PM
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Default RE: OS 46 VF versas OS 46 VR DF

Quote:
ORIGINAL: Rudeboy

The VRDF is a fan engine... it has to be piped and turns 22,000+ rpm ideally...

I don't know what kind of plane that Vertigo is, but unless you intend to do 180 mph with it, go with the VF engine....
It looks like the same pipe would fit the VF. In my application no pipe will be used. The Vertigo is a VTOL plane that has a the engine in a nacelle that rotates for verticle or forward flight. The designer says not to use a pipe.
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Old 07-12-2004, 08:26 PM
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Default RE: OS 46 VF versas OS 46 VR DF

I see... I think I know what Vertigo you are talking about.

In that case the VRDF is the way to go.
It will not realise it's full potential without a pipe, but you definitely need the power (rpms) from this engine to get this plane going... since you are restricted in prop size. I believe the original had a three bladed prop and a df engine for the same reasons.
Using a pipe on this design would obviously be a PITA.

Where did you get the plans for this thing...? I have been interested in it since I first read about it some 15 years ago...
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Old 07-12-2004, 10:11 PM
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Default RE: OS 46 VF versas OS 46 VR DF

Yeah, but I bet due to the timing, a VF without pipe would turn better than a VRDF without pipe. Without a pipe, the sleeve of the VRDF is gonna spit a lot of fuel out that the VF would burn, just my thinking on the deal. I personally would do everything possible to run a pipe on either engine, just know that the VF really has very conservative exhaust duration...not really even pipe-timed. I'd still go with the VF.
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Old 07-13-2004, 12:19 AM
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Default RE: OS 46 VF versas OS 46 VR DF

Seeing as how ifly has got both types it'd be interesting to know if there's any difference in the port timings between the two. As Chuck said, the VF has quite conservative exhaust timing (my 40VF has 140 degrees total) but I've always been under the impression they were designed as a DF engine as well. Both types came out at about the same time so I'd have guessed they both used the same liner.
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Old 07-13-2004, 01:12 AM
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Default RE: OS 46 VF versas OS 46 VR DF

And where does the VX fit in here?
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Old 07-13-2004, 04:57 AM
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Default RE: OS 46 VF versas OS 46 VR DF

Quote:
ORIGINAL: downunder

Seeing as how ifly has got both types it'd be interesting to know if there's any difference in the port timings between the two. As Chuck said, the VF has quite conservative exhaust timing (my 40VF has 140 degrees total) but I've always been under the impression they were designed as a DF engine as well. Both types came out at about the same time so I'd have guessed they both used the same liner.
Good idea, when I get time and a degree wheel, I'll attempt to measure the timings and report here.

Thanks to all for their comments.
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Old 07-13-2004, 05:24 AM
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Default RE: OS 46 VF versas OS 46 VR DF

A degree wheel you'll get here:

Thread: Hop up your two stroke engine.
(Post No. 6)

http://www.rcuniverse.com/forum/m_18...tm.htm#1873945
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Old 07-13-2004, 10:58 AM
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Default RE: OS 46 VF versas OS 46 VR DF

I have both, a degree wheel, and can scrounge up some time.

I've run the VRDF on a Diamond Dust, it seems like it had conservative timing for a DF engine, but still quite a bit longer duration than the VF. I'm thinking maybe 172 on the exhaust duration.

And Razor, I have a 46 VXDF also
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Old 07-14-2004, 06:10 PM
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Default RE: OS 46 VF versas OS 46 VR DF

BTW, The Vertigo I am talking about is in Model Airplane News (MAN) August and September of 1994 by Tom Hunt. Plan number is FSP08941.

Thanks for all of your replies.
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Old 07-14-2004, 07:34 PM
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Default RE: OS 46 VF versas OS 46 VR DF

I had forgotten to do any measurements..I'll post back in a bit.
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Old 07-14-2004, 08:40 PM
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Default RE: OS 46 VF versas OS 46 VR DF

OK
OS 46 VF is 148 degrees exhaust duration.
OS 46 VRDF is 168 degrees exhaust duration.

And for Razor:

OS 46 VXDF is 175 degrees exhaust duration.

Exhaust duration is all I checked, all I was talking about was spitting excess fuel out due to too much exhaust duration without a pipe.

Some pics. All, VRDF, VF, VXDF.
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Old 07-14-2004, 09:15 PM
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Default RE: OS 46 VF versas OS 46 VR DF

Quote:
ORIGINAL: ChuckAuger

OK
OS 46 VF is 148 degrees exhaust duration.
OS 46 VRDF is 168 degrees exhaust duration.

And for Razor:

OS 46 VXDF is 175 degrees exhaust duration.

Exhaust duration is all I checked, all I was talking about was spitting excess fuel out due to too much exhaust duration without a pipe.

Some pics. All, VRDF, VF, VXDF.
Chuck,

With the measurements you have taken and your comment about loosing fuel without a tuned pipe for the VRDF, it appears to me that in my application the VF would be the best fit. I do see now how the longer duration would allow the pipe to stuff the chamber.

Very interesting indeed. Thanks for your effort.
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Old 07-14-2004, 09:27 PM
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Default RE: OS 46 VF versas OS 46 VR DF

Yeah, but the VF won't get the plane off the ground...

Don't know if you've seen it, but there's a construction article [link=http://www.rcgroups.com/links/index.php?id=4453]HERE[/link]
You can see in that article what the guy used for exhaust... very simple... less noise... and tank pressure (very important).

There's also a video here [link=http://www.rcgroups.com/articles/rcpowermag/2004/may/vertigo/Vertigo%20at%20Lake%20Wales%202002.wmv]VERTIGO VIDEO[/link]
You can clearly tell from the video that the power from the newer and more powerful VXDF engine is just barely enough to get the plane to take off vertically... so the slow revving VF isn't going to cut the mustard, you can count on that!
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Old 07-14-2004, 09:34 PM
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Default RE: OS 46 VF versas OS 46 VR DF

Quote:
ORIGINAL: Rudeboy

Yeah, but the VF won't get the plane off the ground...

Don't know if you've seen it, but there's a construction article [link=http://www.rcgroups.com/links/index.php?id=4453]HERE[/link]
You can see in that article what the guy used for exhaust... very simple... less noise... and tank pressure (very important).

There's also a video here [link=http://www.rcgroups.com/articles/rcpowermag/2004/may/vertigo/Vertigo%20at%20Lake%20Wales%202002.wmv]VERTIGO VIDEO[/link]
You can clearly tell from the video that the power from the newer and more powerful VXDF engine is just barely enough to get the plane to take off vertically... so the slow revving VF isn't going to cut the mustard, you can count on that!
I have both the magazines and the plans for the plane. You are probably right but when I do get close to building the plane I may mount both engines and do a static RPM test on them, using the same exhaust setup of course.

Thanks for the links, especially the video one.
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Old 07-14-2004, 09:53 PM
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Default RE: OS 46 VF versas OS 46 VR DF

Well if the VF won't get it off the ground, I sure wouldn't waste my time or money on the VRDF or VXDF. Seems like a larger engine is called for (and realize that the VXDF is a very heavy engine for a .46). I haven't seen the plane or the video, but I'd be re-evaluating my engine choices right about now.
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Old 07-15-2004, 01:12 AM
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Default RE: OS 46 VF versas OS 46 VR DF

Thanks! Guess I need to shop for one of these for my Whip-
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Old 03-03-2005, 12:56 AM
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Default RE: OS 46 VF versas OS 46 VR DF

hi could u tell me what a os 40 vf engine is used for originally?
the proper rpm range?
if its good for the DD?
the proper proppellerto get the most speed?
nitro to run them at
and the perfect pipe?


tanx
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Old 03-17-2005, 06:15 PM
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Default RE: OS 46 VF versas OS 46 VR DF

I am interested to hear the specs on the 40VF as well. I was thinking of putting one on a Diamond Dust. Can anyone help out here?
Thanks!
Myles
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Old 03-18-2005, 10:50 AM
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Default RE: OS 46 VF versas OS 46 VR DF

The O.S. Max "V" series of engines were essentially similar the "FSR" series, except that they had rear exhausts. That was to make it easy to put a tuned pipe in a fuselage tunnel. The "VF" was a front-intake engine, and the "VR" was a rear intake engine. The "FSR" engines and "VF/VR" engines had the same carburetors. The "VF/VR" engines were primarily intended for F3A Pattern flying.

The ducted-fan engines were ported for the high RPM required in ducted-fan use, and also required a tuned pipe to develop that RPM.
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