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BTE DELTA VORTEX ENGINE-OS .91FX vs 1.20AX

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Old 06-05-2007, 08:08 PM
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airbusdrvr
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Default BTE DELTA VORTEX ENGINE-OS .91FX vs 1.20AX

Recently I purchased a Bruce Tharpe Engineering Delta Vortex kit, http://www.btemodels.com/vortex.html. I am planning a retract gear installation similar to the build, http://www.deltavortex.com/neil.htm. Currently I fly the Modeltech ARF of this plane and have an OS 91 FX installed. I could use the existing OS 91FX or buy an OS 1.20AX which is similar in size but a bit more power. The down side I see to the 1.20 is that it seems to be a slower RPM engine requiring larger diameter props. Would I be able to get good top end speed with the slower rpm engine and higher pitch prop or should I try to use the higher rpm OS 91 FX?
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Old 06-05-2007, 09:32 PM
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Default RE: BTE DELTA VORTEX ENGINE-OS .91FX vs 1.20AX

This may not be what you want to hear, but........ both engines will fly it fine, but never fast. This is a big airplane, mine had a Rossi .60 with a tuned pipe and flew great but I don't think it ever when 100 mph even straight down. With retracks you may push 100mph, but not much more.
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Old 06-06-2007, 04:42 AM
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Default RE: BTE DELTA VORTEX ENGINE-OS .91FX vs 1.20AX

I had actually thought about using the performance 60 size engine instead of the OS 91/1.20. I have a Rossi 61 and YS 61(both rear exhaust) in other planes and they are real screamers. I hate to cannibalize either of those airplanes and those type engines are hard to find now. Of course, a Jett engine would work great. But do I want to invest that much money in a plane like the Vortex?
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Old 06-06-2007, 07:09 AM
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Default RE: BTE DELTA VORTEX ENGINE-OS .91FX vs 1.20AX

I dont think you would regret getting the jett and theres no rule saying it would have to stay in the vortex is there
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Old 06-06-2007, 01:03 PM
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Default RE: BTE DELTA VORTEX ENGINE-OS .91FX vs 1.20AX

Guys:
HaveBlue is right on the money, but lets get to first things first. The BTE bird is a great flying sport wing. It is not now, or ever intended to be fast, regardless of what you put on it, so go to a known fast airframe and quit kicking a dead horse. Again, lets be frank and honest about engines. The OS is a decent sport engine, intended to idle and transition well and be user friendly. There is only one engine that will give you the best of both worlds, and that is a Sports Jett engine. If you are doing 3D or trying to go faster, its a engine well woth every penny of the cost. I have them all from the 35 to the 90, and yet to wear one out, so they are cheep in the long run. Be sure to purchase the LX version of the Sports engines, its good for more rpm and the general handeling and user friendly traits are still there. I will run you for pinks with a 35 against any and all OS 46's and take yours home every time. Oh, should tell you the 35 has been running hard for now into its 5th year, and just keeps on getting better eash year. I am a admitted die hard Jett fan who's first glow motor was a 1948 Brown, so have had a few. ENJOY Bro 119.

Nice to see Blue around!!!
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Old 06-07-2007, 12:39 AM
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Default RE: BTE DELTA VORTEX ENGINE-OS .91FX vs 1.20AX


OS 91, MACS tuned pipe, APC 13x8, 15% fuel..... 126mph on the flat, using Radar.
Not fast, but fun. I like mine a lot. Do bother to install the airbrakes.

I think the OS 120 would be slower because it wont rev like the 91.

Barry
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