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Nitro models pusher Bobcat?

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Old 11-24-2006, 06:15 AM
  #576  
gehr2box
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Default RE: Nitro models pusher Bobcat?

It's the size of the holes in the booms and the illustrations showing mini servo's (2 mounting holes in servo's vs 4 for standard size). The NLG steering and throttle servo's indicate the larger servo's.
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Old 11-24-2006, 09:15 AM
  #577  
Larry Legg
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Default RE: Nitro models pusher Bobcat?

I think I will be getting a Bobcat 50 for Christmas. I am looking at a Clarence Lee Modified K&B .61 engine for power. Has anyone had any experience with this engine? My other option is a MVVS 40 Quickie racing engine--I am wondering if that is too small for this plane.

Thanks,

Larry
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Old 11-24-2006, 10:10 AM
  #578  
gary don
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Default RE: Nitro models pusher Bobcat?

LARRY, THE K&B IS A GOOD MOTOR, I USED AO.S. 61 ON MY CAT, 10-8 PUSHER PROP. CHANGED THE WIRE LANDING GEAR ON FRONT TO A TWO POLE, MORE STABLE ON LANDINGS. GARY
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Old 11-24-2006, 10:29 AM
  #579  
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Default RE: Nitro models pusher Bobcat?

ORIGINAL: XJet

ORIGINAL: Crazy4Flight
I used Hitec HS-225MG for the rudders and dual elevators, HS-425BB on the ailerons.
Ewwww. Cross your fingers and hope to fly.

Do a search on HS225 problems -- you'll find plenty of them.

I bought three of these (HS225MG) servos and they all stripped out real quick. The problem is the tiny nylon gear that is driven by the motor pinion. It's just 0.8mm (30 thousandts of an inch) thick and has teeth so fine you can barely see them. The slightest knock -- or even a puff of breeze :-) is enough to strip that baby.

I did some tests and found that there is *no* difference in geartrain strength between the MG and the nylon-geared version -- because even with the plain (cheaper) nylon gears, that tiny little cog is always the first to go.

In fact, the only thing you get from the meta-geared version is more slop and faster wear.

I certainly would not trust any model to an HS225, least of all a model capable of traveling at speeds that would make it lethal if you accidentally hit someone.

And, just for the record -- I'm a Hitec fan. I've got over 50 Hitec servos from HS81s through to HS5955TGs. Of all those servos the *only* ones that have *ever* failed me were the HS225 -- and the *all* stripped within a flight or two -- even when used on throttle!
I use a lot of Hitec 225 std and mgs. They are also used extensively in pylong racing (up to 200mph racers) You shouldn't have a problem with them.
They are great servos. I've got them on the ailerons in the bobcat and also use them in a jet. no problems at all. Hitec also carries a great warranty to my understanding although I've never had to use it. Buy them from a reputable dealer.
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Old 11-24-2006, 03:06 PM
  #580  
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Default RE: Nitro models pusher Bobcat?


ORIGINAL: XJet

ORIGINAL: Crazy4Flight
I used Hitec HS-225MG for the rudders and dual elevators, HS-425BB on the ailerons.
Ewwww. Cross your fingers and hope to fly.

Do a search on HS225 problems -- you'll find plenty of them.

I bought three of these (HS225MG) servos and they all stripped out real quick. The problem is the tiny nylon gear that is driven by the motor pinion. It's just 0.8mm (30 thousandts of an inch) thick and has teeth so fine you can barely see them. The slightest knock -- or even a puff of breeze :-) is enough to strip that baby.

I did some tests and found that there is *no* difference in geartrain strength between the MG and the nylon-geared version -- because even with the plain (cheaper) nylon gears, that tiny little cog is always the first to go.

In fact, the only thing you get from the meta-geared version is more slop and faster wear.

I certainly would not trust any model to an HS225, least of all a model capable of traveling at speeds that would make it lethal if you accidentally hit someone.

And, just for the record -- I'm a Hitec fan. I've got over 50 Hitec servos from HS81s through to HS5955TGs. Of all those servos the *only* ones that have *ever* failed me were the HS225 -- and the *all* stripped within a flight or two -- even when used on throttle!

I don't know how you fly but I have never blown out a 225 in flying.



Do a search on any servo and you will find some kind of problem or grip.

I lost the gears in a JR 8231 servo the jet rolled while in my truck and bumped the elevator back driving the servo and the gears failed. IS it a bad servo NO!

Guys fly combat with HS81 HS-85 get hit mid air servo loosses it gears are the servos bad or faulty NO!
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Old 11-24-2006, 10:18 PM
  #581  
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Default RE: Nitro models pusher Bobcat?

ORIGINAL: Crazy4Flight
I don't know how you fly but I have never blown out a 225 in flying.
Well I exercise all my servos before flying them and the first HS225 ate its geartrain while just cycling with no load on it on the bench. Started okay then, after about a minute, began making awful noises -- then jammed up solid.

The second one stripped out running throttle on a 40-sized profile -- all it had to do was rotate the barrel on a TT46Pro and it stripped out first-flight. Note that the endpoints were set perfectly and the throttle linkage even had a W bend to take out the vibration -- but it still failed. I replaced the 225 with a 425 and two years later, *that* servo is still working just fine.

So I haven't been loading them up with big (or any) flying surfaces and they haven't been knocked around on the ground.

When I first has problems I did a search and found that *some* folks had experienced very similar problems (plus worn pots, bad centering and blown motors). Others had experienced no problems at all.

The difference seems to be that those who like the 225 tend to have *very* small control surfaces with very little throw. This actually puts only a tiny load on the servo so the weak-point gear isn't stressed to failure. Where Hitec comes unstuck is they way they promote this servo as the "mighty mini" and suggest torque ratings in line with a standard servo.

I don't know how big the flying surfaces on the Bobcat are or whether they'll overload the wimpy 225's gearset, but I don't think that *I* would be prepared to take the chance, especially when there are a lot of far more capable servos out there which I know are far more robust.

What about that third HS225MG servo I had?

Well I decided to test the torque claims made by Hitec so I set up a test rig. The gear stripped at less than 85% of the rated torque. I replaced the metal gearset with a nylon set and the same gear still stripped at the same torque -- meaning the cost of a metal set is just a waste of money!

Do a search on any servo and you will find some kind of problem or grip.
True -- but in the case of the 225 the number of gripes is inordinately high. *Lots* of people have had problems with them -- whereas most other models have only got a tiny number of moans.
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Old 11-25-2006, 02:15 AM
  #582  
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Default RE: Nitro models pusher Bobcat?

I briefly considered the two and a quarter until I read this cautionary note in an ad.
Note: While the torque value is very high on this servo, it is still a mini size servo so the gears are not as strong as a standard servo.
As in all the model stuff we buy, it is up to the user to determine the suitability for the particular application and make an informed decision.

Anyways, back to the Bobcat.......
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Old 11-25-2006, 03:19 PM
  #583  
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Default RE: Nitro models pusher Bobcat?

Two questions. 1. Do you think one profile servo(70 to 75 os of torque)would work on the elevator?
2. I just bought a Rossi 60 at a very good price, what do you think of that vs a OS 61 FW. Look forward to your opinions. Joe
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Old 11-25-2006, 03:29 PM
  #584  
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Default RE: Nitro models pusher Bobcat?

I have been flying a Bobcat for the past couple of weeks with an OS 55ax. I have about 12 flights in so far. I am using a single HS125 servo (41.6 oz-in torque) for the elevator. I have done numerous full power dives, tight turns and vertical pull ups. Not had any problems to date.


ORIGINAL: JL636

Two questions. 1. Do you think one profile servo(70 to 75 os of torque)would work on the elevator?
2. I just bought a Rossi 60 at a very good price, what do you think of that vs a OS 61 FW. Look forward to your opinions. Joe
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Old 11-25-2006, 04:31 PM
  #585  
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Default RE: Nitro models pusher Bobcat?

The elevator is not that big, and the travel is extremely limited by the bevel on the leading edge, so I am also going with a 42 oz servo inside the stab..
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Old 11-25-2006, 04:31 PM
  #586  
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Default RE: Nitro models pusher Bobcat?

Continuing flight report, 12 flights:

- Noticed a slight pitch trim change between full and empty tank. One or two clicks of trim needed between the fuel tank extremes. Pitch becomes a little more sensitive near the end of a tank. I had thought about moving the CG back a bit, but wonder now how much the trim would change by the end of the tank.

- Landing gear still holding up well. Our field is grass and bumpy. (Drilled holes in front of and behind mounting blocks and poured in 5 min epoxy to make sure blocks were secure)

- Trim has come loose here and there (even after ironing before 1st flight). I had a large part of the blue trim on one wing shed it's clear top layer. The piece hung on and was large enough to effect low speed stability.

- No degradation of painted parts from fuel exposure (15% nitro)

- Slows down pretty quick below 1/2 throttle. If you need to dead stick you will not have a lot of time to pick a landing spot. I've had 3 dead sticks, 1 due to loose/lost glow plug and two caused by failed clunk fuel line (used old line, split at both ends).

- No engine mixture problems noted with tank facing forward and long lines running back to motor.

- Canopy is screwed on (8 small screws) and seems to be staying put. No cracking noted.

- T/O roll is around 75ft.

- Reduced ail throw for low rate to about 30mm total travel. The recommended 50mm total throw is excessive for most flying I do. It rolls plenty fast with the lower rate. Would make for an interesting 1st flight with the recommened throws without expo!

- No problems noted with the engine mount system. Engine has stayed tight (potted in Silicone RTV) in the mounting.

- Nothing aside from a little covering trim has come loose in flight.

- I limit flight duration to around 11 minutes. I have my timer set for 10 minutes and fly full thottle most of the time. After landing I have a couple of ounces of fuel left max.

- OS 55ax has been an easy starting and reliable motor.


Bud
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Old 11-25-2006, 04:38 PM
  #587  
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Default RE: Nitro models pusher Bobcat?

- Reduced ail throw for low rate to about 30mm total travel. The recommended 50mm total throw is excessive for most flying I do. It rolls plenty fast with the lower rate. Would make for an interesting 1st flight with the recommened throws without expo!
That is for the ailerons, right?

A couple of people looking at my kit have commented on how some of the hardware looks a lot like hanger 9 stuff. When shrinking the wrinkles in the covering, it sure behaved a lot like Ultracote. and the When it came time patch the stab after some surgery, the Ucote bright yellow as a perfect match....Hopefully it is just the trim that is the lower quality stuff..
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Old 11-25-2006, 04:53 PM
  #588  
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Default RE: Nitro models pusher Bobcat?

Yup reduced aileron throw. I still have the 50mm available on high rates. I pretty much left the elevator throw stock. I juggled the expo a bit to get a comfortable feeling for my style of flying.

On my elevator and rudder servo mounting (used 2 HS125's on rudder as well, needed to carve a bit to get a flush mount) I covered the servo openings with yellow monocote and it looks like a perfect color match as well. I thought about making some covers, but the monokote generates less drag and no screw heads... and it was easier to get done quickly so I could fly it that weekend.

ORIGINAL: Wayne22

- Reduced ail throw for low rate to about 30mm total travel. The recommended 50mm total throw is excessive for most flying I do. It rolls plenty fast with the lower rate. Would make for an interesting 1st flight with the recommened throws without expo!
That is for the ailerons, right?

A couple of people looking at my kit have commented on how some of the hardware looks a lot like hanger 9 stuff. When shrinking the wrinkles in the covering, it sure behaved a lot like Ultracote. and the When it came time patch the stab after some surgery, the Ucote bright yellow as a perfect match....Hopefully it is just the trim that is the lower quality stuff..
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Old 11-27-2006, 07:06 AM
  #589  
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Default RE: Nitro models pusher Bobcat?

NEW QUEEN OF MY HOME
-I have had to change the color scheme because of the seperation of the translucent films of the trims when took place ironing the top of the wings.
-Magnum XLS 52 with tower muffler. 11X7 p prop. Stock wood blocks were used. Replaced the engine mounting screws and used silicone to fill the gaps under the engine as described in this forum.
-Replaced main gears with carbon fiber ones while placing them 2.5 cm front and 2.5 cm lateral sites from the original as mentioned in this forum.
- Built in a compact fashion using 30 min epoxy. Wing halves were attached to the body with epoxy and screws as described in this forum.
-One elevator servo (HS 125), two mini servos for rudders and std servos(rest of them) were used as suggested in this forum.
-Total dry weight 2.7 kg without cg adjustment.
Waiting for throw and cg adjustments.
Waiting next saturday for flight

THANK YOU VERY MUCH FOR ALL THE CONTRIBUTORS OF THIS FORUM FOR THEIR ENORMOUS KNOWLEDGE AND EXPERIENCES.
YOU ARE GREAT.
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Old 11-27-2006, 08:23 AM
  #590  
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Default RE: Nitro models pusher Bobcat?

where did you get the landing gear?
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Old 11-27-2006, 08:31 AM
  #591  
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Default RE: Nitro models pusher Bobcat?

Looks cool. I'm sure the color scheme will help in keeping orientation in flight. These hotrods get far away pretty quick.


ORIGINAL: Selcuk

NEW QUEEN OF MY HOME
-I have had to change the color scheme because of the seperation of the translucent films of the trims when took place ironing the top of the wings.
-Magnum XLS 52 with tower muffler. 11X7 p prop. Stock wood blocks were used. Replaced the engine mounting screws and used silicone to fill the gaps under the engine as described in this forum.
-Replaced main gears with carbon fiber ones while placing them 2.5 cm front and 2.5 cm lateral sites from the original as mentioned in this forum.
- Built in a compact fashion using 30 min epoxy. Wing halves were attached to the body with epoxy and screws as described in this forum.
-One elevator servo (HS 125), two mini servos for rudders and std servos(rest of them) were used as suggested in this forum.
-Total dry weight 2.7 kg without cg adjustment.
Waiting for throw and cg adjustments.
Waiting next saturday for flight

THANK YOU VERY MUCH FOR ALL THE CONTRIBUTORS OF THIS FORUM FOR THEIR ENORMOUS KNOWLEDGE AND EXPERIENCES.
YOU ARE GREAT.
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Old 11-27-2006, 09:10 AM
  #592  
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Default RE: Nitro models pusher Bobcat?


ORIGINAL: knowcrash

where did you get the landing gear?
I bought them from our local hobby shop in Ankara, Turkey. The brand of it HOBBYSQUADRON. It cost me about 22 USD.
I found the front gear again in my local hobby shop in used parts section. So there is not any brand written on it.
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Old 11-28-2006, 04:35 AM
  #593  
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Default RE: Nitro models pusher Bobcat?

have you flown your bobcat.im getting 1 in 2 weeks.do you think it is good to train with it because ive got a turbine saab viggen and i need to fly something that will make me learn thanks i need advise
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Old 11-28-2006, 05:32 AM
  #594  
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Default RE: Nitro models pusher Bobcat?


ORIGINAL: kenazzo2000

have you flown your bobcat.im getting 1 in 2 weeks.do you think it is good to train with it because ive got a turbine saab viggen and i need to fly something that will make me learn thanks i need advise
Not yet. The manual with the plane is not satisfactory. I suggest you to follow the mods written in this thread.
I think the most important thing, at first, is to decide to build it in a compact fashion or seperatable one.
Then, you can find the most experienced modelers and pilots on it here.
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Old 11-28-2006, 05:58 AM
  #595  
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Default RE: Nitro models pusher Bobcat?

Next to a 428 class Q500 pylon racer I'd say the Bobcat would be a good training aid toward flying a turbine. It's fast and the sweep in the wing will display behavior similiar to most jet planforms. It can be landed fast if desired, but slows down to around pattern plane landing speeds. The pusher prop helps to get you familiar with controling a plane without the benefit of prop blast directly on the controls.

Make no mistake though, while fast, it is only 1/2 to 2/3 the speed of most jets I have seen. It's relatively light, has a flat bottom airfoil, no flaps or retracts. Pricewise I don't know if you could find a less expensive jet trainer. A 428 Q500 would get you closer to jet speed, but the motor needed to get that speed would set you back a few dollars (but cheap compared to the turbine!)

My $.02 worth.

ORIGINAL: kenazzo2000

have you flown your bobcat.im getting 1 in 2 weeks.do you think it is good to train with it because ive got a turbine saab viggen and i need to fly something that will make me learn thanks i need advise
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Old 11-28-2006, 07:50 AM
  #596  
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Default RE: Nitro models pusher Bobcat?

This plane will be much easier to fly than your Viggen. I would fly this one and only fly the Viggen with a buddy bix until you feel your skills are good enough. You may want to program throttle lag to match your turbine.

Mark
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Old 11-28-2006, 01:27 PM
  #597  
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ORIGINAL: MMallory

This plane will be much easier to fly than your Viggen. I would fly this one and only fly the Viggen with a buddy bix until you feel your skills are good enough. You may want to program throttle lag to match your turbine.

Mark
this is my vigen i hope the bobcat helps me thanks for all of your help
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Old 11-28-2006, 01:38 PM
  #598  
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Default RE: Nitro models pusher Bobcat?

Nice plane. You should have a lot of fun with it. Just don't bank and yank. Keep the speed up by not making really tight turns. Delta's slow down real quick if you are not careful.

I had one I sold years ago, I wish I kept it.

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Old 11-28-2006, 06:45 PM
  #599  
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Default RE: Nitro models pusher Bobcat?

Mine finally showed up today. Very nice looking.

Time to get to work...... Just read through all the posts again to check out the mods.
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Old 11-28-2006, 08:53 PM
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Default RE: Nitro models pusher Bobcat?

Cool beans. Careful on the fast low passes, it get's to be habit forming.

What motor are you going to use?


ORIGINAL: thebluemax

Mine finally showed up today. Very nice looking.

Time to get to work...... Just read through all the posts again to check out the mods.
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