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Nitro models pusher Bobcat?


Old 11-21-2007, 10:11 PM
  #2576  
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Default RE: Nitro models pusher Bobcat?


ORIGINAL: airhog1391

I just purchased a bobcat 46, how will the ax 55 do on this model, I would like some input from experienced pilots. I have never had a pusher, do I need a special prop, or do I just turn any prop around backwards to make it work? I would appreciate any advice that I can get. Thanx!!! Steve.
While it should fly fine with the AX 55, a lot of us are running it with bigger engines for more speed.

A few have also taken to using the AX 55 with a tuned pipe and are getting similiar results to what we are getting with the larger engines.

And YES you need a pusher prop. You cannot run the engine in reverse.

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Old 11-21-2007, 10:19 PM
  #2577  
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Default RE: Nitro models pusher Bobcat?

thanks guys for the info on the ballpark setting for the nuetral elevator setting.
It is very useful.
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Old 11-21-2007, 10:32 PM
  #2578  
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Default RE: Nitro models pusher Bobcat?

Mine "touches" at neutral.

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Old 11-21-2007, 10:49 PM
  #2579  
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Default RE: Nitro models pusher Bobcat?

Has anyone used the Spektrum DS821 in the Bobcat. Specs are below. Anyone see any problem with using them.
Typeigital Hi-Torque
Torque:72 oz/in @ 4.8v, 88 oz/in @6v
Speed:.19 sec/60° @ 4.8v, .15 sec/60° @ 6v
Dimensions (WxLxH):0.74"x1.50"x1.47"
Weight:1.5 oz
Bearing:Single Ball Bearing
Motor Type:3-pole ferrite
Gears:Composite
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Old 11-22-2007, 03:14 AM
  #2580  
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Default RE: Nitro models pusher Bobcat?

If I go w/ os .61, what prop works best on that one? & will the .61 go in the plane w/out any modifications to the fuselage (will it bolt right in) Thanks in advance for your input!! Steve.
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Old 11-22-2007, 07:25 AM
  #2581  
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Default RE: Nitro models pusher Bobcat?

Steve,
Here is my OS 61 install.
You will need to add a spacer under the engine mounts,
I turned my front crankcase 90 degrees so that it will run opposite the normal direction and I do not have to use pusher props. It just sounds like a hassle to find pusher props.
I use a Master Air Screw 11x7 regular prop facing the front of the plane.
You can check my setup info on page #95 post #2369. I changed to the stock OS muffler with a rubber Exhaust Deflector to prevent the muffler from getting back pressure from "head wind".
I do not use Expo, so I had to cut my aileron rates back from the original 25mm to 15mm on high rate and 10mm on low rate.
Good Luck,
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Old 11-22-2007, 08:30 AM
  #2582  
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Default RE: Nitro models pusher Bobcat?

Thanks that is very helpful, How was the .61 to ballance out, I noticed that it is 2 oz. heavier than the .55 ax, did you have to ad wieght or just use your battery placement to ballance? Thanks again. Steve.
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Old 11-22-2007, 10:32 AM
  #2583  
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Default RE: Nitro models pusher Bobcat?

Steve,
I installed my Nicad pack between the former and the nose, I did not add any lead.
John
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Old 11-23-2007, 12:09 AM
  #2584  
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Default RE: Nitro models pusher Bobcat?

The apc11x7 will perform better on it in my opinion.
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Old 11-24-2007, 02:32 PM
  #2585  
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Default RE: Nitro models pusher Bobcat?

airhog1391,
Not sure where you got the specs from but the O.S. 61FX is about 5 ounces heavier than the O.S. 55AX. You most likely will be adding some lead to the nose with the .61FX. Also just some added info to the post about turning the crankcase 90 degrees on the .61, this only works on the older O.S. 61SF engines. The O.S. 61FX has a one piece crankcase and cannot be re-timed to run in reverse.
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Old 11-24-2007, 10:37 PM
  #2586  
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Default RE: Nitro models pusher Bobcat?

I see most put air retracts but have anyone put on mechanical retracts if so what you done or can you lead me in the right direction. Thanks
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Old 11-25-2007, 08:02 AM
  #2587  
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Default RE: Nitro models pusher Bobcat?

This plane really isn't a good candidate for mechanical retracts. You would probably need three retract servos to do it which might drive the total cost of the install higher than pneumatics. It also looks to me like a mechanical install would be a real PITA.
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Old 11-25-2007, 09:05 PM
  #2588  
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Default RE: Nitro models pusher Bobcat?

At this time I can not do pneumatics retract. So I started with my mechanical install. I have completed the rear and will start on the front tomorrow. I post pic of the rear later this week.
ORIGINAL: Stick Jammer

This plane really isn't a good candidate for mechanical retracts. You would probably need three retract servos to do it which might drive the total cost of the install higher than pneumatics. It also looks to me like a mechanical install would be a real PITA.
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Old 11-26-2007, 08:16 AM
  #2589  
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Default RE: Nitro models pusher Bobcat?


ORIGINAL: Stick Jammer

airhog1391,
Not sure where you got the specs from but the O.S. 61FX is about 5 ounces heavier than the O.S. 55AX. You most likely will be adding some lead to the nose with the .61FX. Also just some added info to the post about turning the crankcase 90 degrees on the .61, this only works on the older O.S. 61SF engines. The O.S. 61FX has a one piece crankcase and cannot be re-timed to run in reverse.
I have and several older engines but have never experimented with reversing engine rotation. Which direction should the crankcase be rotated? Is the performance affected?

Bill
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Old 11-26-2007, 08:41 AM
  #2590  
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Default RE: Nitro models pusher Bobcat?

My Bobcat .50 comes in VERY VERY HOT on landings, so I cannot even fathom landing it without rudders.

Since I land on an asphalt RC runway, it eats up 500 feet landing and slowing down. Rudders are essential to keep it lined up until the wheel gets some authority.
Hot landings. I have several overweight Kougars that come in very hot. I use snubber brakes by fitting rubber tubing between the wheel and the collar or sometimes over the collar. It takes only a slight drag to stop the airplane when landing. Take off is not affected since the drag is very light.

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Old 11-26-2007, 11:25 AM
  #2591  
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Default RE: Nitro models pusher Bobcat?

If your bobcat comes in HOT for a landing, you aint landing right !

She should come in nice and gentle with very easily obtained high AOA.
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Old 11-26-2007, 02:53 PM
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Default RE: Nitro models pusher Bobcat?

Hi,

I just received my Nitromodels BobCat 50. I ordered the fix gear version however the one I got has also the holes for installing retracts. The assembly manual is very bad and it just shows pictures of the assembly steps. I am having trouble figuring out how to install the fix landing gear on the wings, the photos shows a piece of wood that should be inserted first inside the wing, but it's not the same shape as the one included on the ARF. Any suggestions?

If I wanted to install rectracts, which brand and model of retracts should I buy?

Thanks.
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Old 11-26-2007, 02:55 PM
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Default RE: Nitro models pusher Bobcat?

What size and brand of air retracts and struts are you guys using on the NitroModels Bobcat 50?
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Old 11-26-2007, 06:35 PM
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Default RE: Nitro models pusher Bobcat?

Original: BillS

I have and several older engines but have never experimented with reversing engine rotation. Which direction should the crankcase be rotated? Is the performance affected?
I've never done this but if the engine has a bolted front case I believe it can be rotated 90 degrees in either direction. You will probably want to rotate it so the carb is on the left side of the plane simply because the throttle cable is set up there. From what I've read on this the performance is not affected but keep in mind the crankshaft is now turning in the direction that can loosen the prop nut so be sure it's extra tight.
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Old 11-26-2007, 06:55 PM
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Default RE: Nitro models pusher Bobcat?

Thanks for the info, but I dont think that I'm going to try to mess with the engine like that, I'll just order some pusher props, that sounds much easier to me. Thanx!! Steve.
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Old 11-26-2007, 06:55 PM
  #2596  
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Default RE: Nitro models pusher Bobcat?

Caiman,

I used Sring Air 100 series 3/16 wire struts. www.retracts.com It comes with a "pull-pull" nose gear steering setup. I also got the Dubro 2-56 "pull-pull" hardware kit which simplifies setup.
Some of the other folks have used Robart gear, but they were on back order for 2 months.
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Old 11-26-2007, 06:56 PM
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Default RE: Nitro models pusher Bobcat?

Hot landings. I looked at a completed Bob Cat this afternoon and the weight was 7 pounds and 9 oz without engine, without tank, and with only one servo. Sheeting the wings might not be a good idea.

Bill
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Old 11-26-2007, 07:10 PM
  #2598  
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Default RE: Nitro models pusher Bobcat?

Are most of you guys running ax.55 or is .61 fx the way to go, I ordered a .61 but know I'm wondering if I'm going to be to heavy, I dont want to come in to hot, I'm wondering if a ax .55 would have been a better way to go. This is my 1st Bobcat & I would like to set it up right the first time. I would like any input you may have. Thanx!! Steve.
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Old 11-26-2007, 07:28 PM
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Default RE: Nitro models pusher Bobcat?

drBobSmith,

From the following Spring Air web site, which retracts exactly did you use?

http://www.retracts.com/Retrax_100.htm

Where did you buy the Dubro 2-56 "Pull-Pull" kit, could you give me a link?

Thanks.
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Old 11-26-2007, 09:51 PM
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Default RE: Nitro models pusher Bobcat?

airhog1391,
I have the .55AX on mine with an APC 11x7 pusher prop using 15% CoolPower and it's a great set up for this plane. The plane balances out nicely at 10.3" without any lead and without having to find a way to secure the Rx battery all the way in the nose. My battery is right behind the nose gear former. A lot of people have gone with this engine and I don't think you'll find any complaints.
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