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Nitro models pusher Bobcat?

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Old 09-07-2009, 04:28 PM
  #3851
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Default RE: Nitro models pusher Bobcat?

Polishedbrother!

Looks like a cool project! I know someone who did something similar, they ran the tuned pipe in the fuselage to keep the lines nice. Try to get your tank right over the CofG, you've got around 2lb of fuel there which will make balance interesting as the fuel burns off. if the fuel lines are long consider a pump. OR fit a turbine.... or you could fit a turbine....has anyone suggested it may be worth fitting a turbine...I'd fit a turbine!!

No seriously, it will be a cool project. best of luck!
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Old 09-07-2009, 04:33 PM
  #3852
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Default RE: Nitro models pusher Bobcat?

Just an idea, but before drilling out the nipple for the tygon, note that the black stuff is also good if it's dubro- dubro sells smoke tubing, and that's what I believe it is- Also, the tygon will melt on the exhaust, and the black "high temp" tubing will not.
Other than that, it sounds like you've got a sound plan that should work quite well-
KM
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Old 09-07-2009, 05:04 PM
  #3853
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Default RE: Nitro models pusher Bobcat?

yea you are right about the Tygon melting, I have been warned about that from someone at the field. I will use a short length of the black stuff on either side of the pre-heter.
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Old 09-09-2009, 05:06 PM
  #3854
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Default RE: Nitro models pusher Bobcat?

Got some mould release oil arriving on Friday from someone at work. I dont know what the specs are yet, I'll give it a go and post the results.
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Old 09-10-2009, 07:36 AM
  #3855
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Default RE: Nitro models pusher Bobcat?

Hi Guys, Lots of great info here but so much to read when you are are trying to find something quickly.After a hard landing on the second flight (engine failure) I need to make a new nose wheel bulk head.
Does anyone know if there is a link in this thread to a template or plan?

Cheers All.
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Old 09-10-2009, 10:43 AM
  #3856
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Default RE: Nitro models pusher Bobcat?

Slight change of topic here...

I have the ".60" sized version of this bird.. I haven't even opened the box yet...

Anyway.. I'm thinking of putting twin EDFs on it instead of a pusher prop... Kind of like an A-10.

Any thoughts/comments??? Suggestions?

I have been doing a little searching, and I'm not coming up with any info that says "_____ edf will produce similar thrust as ___ glow and ___ prop."
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Old 09-10-2009, 10:46 AM
  #3857
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Default RE: Nitro models pusher Bobcat?

There is a guy on rcgroups that did that and hit 180mph with the 63" version. His is ridiculously powered.

Brian



Quote:
ORIGINAL: vmsguy

Slight change of topic here...

I have the ''.60'' sized version of this bird.. I haven't even opened the box yet...

Anyway.. I'm thinking of putting twin EDFs on it instead of a pusher prop... Kind of like an A-10.

Any thoughts/comments??? Suggestions?

I have been doing a little searching, and I'm not coming up with any info that says ''_____ edf will produce similar thrust as ___ glow and ___ prop.''
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Old 09-12-2009, 11:01 AM
  #3858
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Default RE: Nitro models pusher Bobcat?

Video of my Bobcat 52!

http://www.youtube.com/watch?v=JuwsbadHYJs

Make sure to watch in HD when its ready, I just uploaded it.
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Old 09-12-2009, 07:34 PM
  #3859
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Default RE: Nitro models pusher Bobcat?

Hi Guys,

A bit of progress today... The first stage of installing the smoke system was to re-rout the exhaust through the side of the fuz and out of the bottom, this involved taking out the tank (which took about 2 hours to fit nicely in the first place!) and cutting a couple of holes, for the silicon exhaust tube. I have protected the tube from the relatively sharp edges of the fuselage with cable glands (bottom one not shown).
Before I committed to cutting holes in the lovely fuselage I did some engine tests with different exhaust configurations to see the effect of the long exhaust tube on RPM, I decided if there was a significant drop in power I would abandon the project as I do not want to slow her down too much! The engine is an ASP .61 with a 'super quiet exhaust' the exhaust has a removable centre section and a baffle which can be removed or moved between the front and rear of the centre section, this gives a few possible configurations which all have effects on power vs noise. I was hoping that if I removed the baffle and the centre section I would get more power and the silicon pipe would enter the fuz towards the rear well out of the way of the fuel tank and the rear ply former. Anyway I did the engine tests and was surprised and ultimately pleased with the results...

I let the engine cool between each test and used the same APC 11X7 prop.

1) Original tried and tested configuration:
centre section in place, baffle fitted at the front of the centre section (closest to the cylinder), standard short exhaust deflector fitted....12,720 RPM

2) As above but with 300mm blue silicon tube fitted in place of the standard exhaust deflector....13,260 RPM (!)

3) Centre section in place but baffle removed, 300mm blue silicon tube fitted.... 13,530 RPM

4) Centre section in place now with the baffle fitted at the rear of the centre section (farthest from the cylinder), 300mm blue silicon tube fitted.... 13,700RPM

5) Centre section removed baffle fitted (shot exhaust configuration), 300mm blue silicon tube fitted (this setup was MUCH louder).... 13,000-13,200 RPM

I decided at this stage to run with option 4! I was getting close to a 1,000 RPM increase from my original configuration and the engine was quieter too....must admit I was not expecting that!!
it did mean however that as the exhaust wasn’t going to end up any shorter the silicon exhaust tube would clash with the fuel tank where it entered the side of the fuz resulting in an internal re-shuffle!
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Old 09-22-2009, 04:55 PM
  #3860
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Default RE: Nitro models pusher Bobcat?



The Bobcat smoke system continues!

The following pics are pretty self explanatory, they show the fitting of the perry valve in the back plate and the rather agricultural pre-heater coil. Ihave since wrapped the coil with fiberglass loft insulation and aluminium tape to help keep the heat in.

More to follow...

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Old 09-22-2009, 05:21 PM
  #3861
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Default RE: Nitro models pusher Bobcat?

Hey Guys thanks for all the info on the Bobcat. I have mine balanced now and it flies beautiful. LAnds on it's own. I tried to hep it once. Big mistake. Only weakness I have founds is the nose gear between the servo and the landing gear. Once that is modified, next stepis to add smoke. It currently has on OS .61 Does great fly by's and is very stable. Needs more speed still.
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Old 09-24-2009, 05:23 PM
  #3862
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Default RE: Nitro models pusher Bobcat?

Hi Guys,
Got the engine back on with the smoke muffler fitted, its not a neat as I would of liked and I’m not rally happy with the pre-heater. I have ordered some 1/8” soft copper brake line as I have read this can be coiled much tighter than the brass tubing that I made the pre-heater with. If this is the case I will redo it as I would like to get another couple of coils around the exhaust to give the smoke oil the best chance of vaporising…and tight coils will look better.
Next jobs are to refit the fuel tank, this will need to go ½” further forward of the original position and will need a mounting plate. Then fit the oil tank, the smoke valve & servo, filler and vent lines for the oil tank, a needle valve for flow control and squeeze the receiver in somewhere.
More to follow, hopefully with a test vid…
Chuck
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Old 10-07-2009, 05:50 AM
  #3863
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Default RE: Nitro models pusher Bobcat?

BTW, I finally found a supplier to make clear bobcat 50 canopies for me. Anyone interested? Let me know, just PM me. He's charging 10$ per piece, plus shipping and handling. The first batch will probably come out end October.
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Old 10-23-2009, 04:58 PM
  #3864
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Default RE: Nitro models pusher Bobcat?



Does anyone out there have a copy of the instructions for the Nitro Models Bobcat Pusher jet 50.  If anyone has them could you copy and email me these instructions.  I contacted Nitro Models and they flat refused to send me them.  I bought the model at my local hobby store.  He said he bought it from a friend and there were instructions.  Please email them to me at skybird17@juno.com.  Thanks in advance

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Old 11-01-2009, 02:57 PM
  #3865
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Default RE: Nitro models pusher Bobcat?

Success!
Check out the Smokin Bobcat video on you tube.

http://www.youtube.com/watch?v=K-m5KZrJ_ss

Do you still need those instructions Skybird?


Chuck.
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Old 11-01-2009, 03:08 PM
  #3866
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Default RE: Nitro models pusher Bobcat?


Quote:
ORIGINAL: SKYBIRD17



Does anyone out there have a copy of the instructions for the Nitro Models Bobcat Pusher jet 50. If anyone has them could you copy and email me these instructions. I contacted Nitro Models and they flat refused to send me them. I bought the model at my local hobby store. He said he bought it from a friend and there were instructions. Please email them to me at skybird17@juno.com. Thanks in advance

I found one. Still in need?
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Old 11-02-2009, 05:06 PM
  #3867
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Default RE: Nitro models pusher Bobcat?

Nope the holes are not there. My "cat" has the wing tube thru the fuselage and 1 each in each wing to fit into the fuse. The strings for the servo wires were taped insite the wing too.
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Old 11-04-2009, 06:13 PM
  #3868
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Default RE: Nitro models pusher Bobcat?

what retracts are you guys using on this?

Shane
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Old 11-05-2009, 04:01 AM
  #3869
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Default RE: Nitro models pusher Bobcat?

I used Pro Lynkx from Digitech Turbines: http://shop.digitech-turbines.com/pr...r9vc4vsdo1qr41

Drop in set that's good for grass operation, has possibly the best brakes I have come across, have a look, only problem is they cost more than the airframe, but then the airframe is very cheap and needs a lot of work to make it airworthy with a turbine.

Mike
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Old 11-05-2009, 08:21 AM
  #3870
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Default RE: Nitro models pusher Bobcat?

This is the set I used http://www3.towerhobbies.com/cgi-bin...?&I=LXJZE2&P=7
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Old 11-07-2009, 09:14 PM
  #3871
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Default RE: Nitro models pusher Bobcat?

Has anyone used a Super Tigre 90 on the Bobcat 51. I am preparing to get mine built and have some concern about the engine being too large. The G90 really doesnt weigh much more than the OS Fx .61. Opinions,???? Thanks, Tom
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Old 11-08-2009, 10:10 AM
  #3872
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Default RE: Nitro models pusher Bobcat?

Hi I have an OS .61 on mine and the biggest problem I have is prop limitation. The motor will put out enough hp to go faster, but because of design I can only go so large on the prop.I am thinking of a higher pitch prop. I have a couple on order now. When I try them out I will let you know.I currently have a cut down 13x6 Right now it is just a guessing game. I also have a "how fast" that I just received so I will be able to make accurate test.

os: altitude here is 4600'
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Old 11-08-2009, 09:08 PM
  #3873
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Default RE: Nitro models pusher Bobcat?

Hello,

Thanks for the response AZRCADDICT! I have read a good bit on this multi page forum and certainly lots to take in on ideas. After doing some research on it, I may wait and put this supertigre 90 on something else and go with a 55AX, I am interested in some good speed, but not Crazy fast. I even considered one of the OS 46vx Df motors with a Ducted fan set up. I never get in to big of a hurry as I normally have 3 or 4 projects going like most of the other RC addicts like me.
Let me know once you get those new props in and how the run and what size. Thanks Tom
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Old 11-08-2009, 10:12 PM
  #3874
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Default RE: Nitro models pusher Bobcat?

4 and 6 degree pitches are usually better suited for 3d. You want to get as close to something like a 9x9 or 10x10 for example. Not sure what diameter and pitch are best for a 60 but on something like Jet .50 I used a 9x9. Will take a long time to get up to speed but then it gives great speed.

Brian

Quote:
ORIGINAL: azrcaddict

Hi I have an OS .61 on mine and the biggest problem I have is prop limitation. The motor will put out enough hp to go faster, but because of design I can only go so large on the prop.I am thinking of a higher pitch prop. I have a couple on order now. When I try them out I will let you know.I currently have a cut down 13x6 Right now it is just a guessing game. I also have a ''how fast'' that I just received so I will be able to make accurate test.

os: altitude here is 4600'
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Old 11-08-2009, 10:31 PM
  #3875
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Default RE: Nitro models pusher Bobcat?

I run an FX61 on mine and have tried a few props and I get the best all around performance from an 11x7. I fly from grass and we can typically see the grass flying when I rotate but I've never had an issue with it. I do have it in my mind I'd like to try a 10x10 but haven't found one yet.

Knowing how mine flies I wouldn't even think about any less motor but might consider more.

I have a few edf's around and I'm sure there are others that will be far more in tune with this but I'm thinking there is no way a 46df is going to fly this thing. DF's are cool but when the ponies count it's usually a bad road to travel. IMHO that is....
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