marktur

Terry, here's the specs:

OS 55AX:
Practical RPM: 2,000-17,000
Power Output: 1.75 ps/16,000 RPM
Weight: 14.25oz (404g)
Recommended Props: 12x7-8, 13x6-7


Tower 75:
Practical RPM Range: 2,000 - 16,500 RPM
Weight: 652g (23.0 oz) (with Muffler)
Horsepower: 2.2 BHP at 15,600 RPM
Recommended Props: Break In: 12x6 or 13x6

So what I'm seeing here is that the OS is 200+ grams LIGHTER and will turn more RPM's. It also calls for a higher pitched prop. The 75 has a bit more HP, but does the tradeoff in size and weight negate that? Also, the physical dimensions of the 75 is significantly larger...so you have more drag from the bigger motor.

Me thinks it's time for a RACE!
I'll put my money on the OS, I think.

OK, time to get away from the PC for a while! It's a BEAUTIFUL day here in Boynton Beach, FL. Check out the beach:
http://www.co.palm-beach.fl.us/webcams/slwi/dig001.jpg

No waves today, can't surf, but I think I'll still go and get wet. I live about 5 minutes away. Lucky me!

scoobystig

hi mate

www.planenutz.co.uk

and the engine they recommend and the one i have fitted is the JEN57

from www.justengines.co.uk

hope this helps

steve

marktur

Quick questions: How did you guys run the elevator servo wire? I don't see a straight path to the rudder from the inside, unless I'm not seeing something...do I need to do surgery to route the wires without seeing them?


I made a nice box for the HS125 to fit in the stabilizer, and I used a bigger full-size servo for the rudder, and I want to couple it to the other one as I saw in previous posts. Can anyone tell me the best way to do this? ie. what did you use for the rod, and what connectors did you use?

I finally turned on the new Spektrum 7 - very nice so far.

Thanks,
Mark

opjose

Here is the link to the main gear: http://www2.towerhobbies.com/cgi-bin...=++&search3=Go

Or search for "LXJZD2"

And here is the link to the nose gear: http://www2.towerhobbies.com/cgi-bin...=++&search3=Go

Or search for "LXJZD6"


Also have a look at this: http://www2.towerhobbies.com/cgi-bin...=++&search3=Go

Or search for "LXET37"

This tank fits perfectly.

opjose

I really haven't seen that many...

I've had VERY good luck with the T.H. and GMS engines. I have close to a dozen of them now.

I'll trade an Evolution for a T.H. of the same size any day. ( of course I'll trade either for an O.S. too! )

The aforementioned problem with the remote valve support breaking is a bit unusual. Normally there is not much force on the assembly, though I could imaging that vibration may played apart in this...

I haven't seen it myself, and it does take a bit of force to bend the metal bracket.

Then again I've also have had O.S. remote needle supports crack right at the bolt area as the metal used on a few engines is a bit to brittle.

Adrians flyer

Well thanks, but I can't take credit for it. I saw it in the Tech Tips section in Model Aircraft, or R/C flyer (getting old is tough) and I thought it was a really great time saver. Just make sure you don't use a shop vac like my brother has! It boast 5hp......yes 5hp........it will suck so hard you could collapse a wing or stretch out you covering to look like an old pair of socks! LOL

Bruce

marktur

OK, I performed surgery, made some holes in the 1/4 balsa stiffeners, coated with thin CA, and ran the wire. I then put it all together for the first time....Wow! I can't wait to fly this weekend! It's a lot bigger than I expected once it all came together. (Not complaining)

Next to the HET F20 I'm building, it's a giant!

So I also pulled out the huge rudder servo I put in, and went with 2 HS81MG's. I will install them both on the same sides of the rudders to make it easy with a Y connector.

still4given

I used a reversing Y for the elevators but with the rudder servos on the outside, one will push as the other pulls so no need for a reversing Y.

Here are some pics of how my poor Bobcat looks after some repair. I decided to just fix it structurally and fly it like that. If it turns out I really like it then I will get another kit and build a new one.

Most of the damage was caused because the servo tray came loose and broke the two formers before and after it. If I were building it again I would epoxy all of that before flying it. I already had done the front formers because the front nose wheel blocks were loose from the start so while gluing them I went ahead and glued the formers too.






I used JB weld on the muffler to make sure it doesn't fall apart again.



Blessings, Terry

XJet

Another option is the ASP52. My Bobcat with an ASP52 flies at around 100mph and is noticeably faster than another I've seen flying with an OS50 so I figure the ASP can't be much less powerful than the 55AX.

The big bonus of the ASP is the price -- around US$60.

This engine has been very reliable and runs like a swiss watch. A great buy and with a 10x7 or 10x8 prop it's a perfect match for the Bobcat.

marktur

Hey - it looks ready to fly! Sounded a lot worse than it looks. Fly the crap out of it, and get another one for retracts, etc. once you're comfortable.

Question: The motor mounts are too thin for the OX55AX crancase. I'd say about 1/8 or so too short. Did you have to raise your 75 up higher?

Thanks,
Mark

marktur

Hi guys,

Here she is, under construction...looks like the pictures...not "mine" yet. I really want to do a nice scale cockpit.

http://gallerielorraine.com/PhotoGal...1/Default.aspx

I hate the tinted canopy! Does anyone know of where I can get a clear replacement for it? It doesn't have to be exactly the same, just needs to fit and not look silly. I wanted to put a decent cockpit and pilot into mine, and the red tint just makes me want to hurl!

Planning for the maiden flight on Saturday!

Thanks,
Mark

still4given

Hi Mark.

This model does have retracts.

Yes I did have to raise the 75 up. I didn't use the stack motor mounts at all. I made new ones out of aluminum. I wanted something solid. I read too many post where guys were having trouble with the soft mounts anyway.

Blessings, Terry

opjose

Very nice.

Wish I had seen these before ordering mine.

marktur

OPJose - send them back and get the nice ones from Robert. Very nice to deal with, and I paid on Sunday - he sent me Fedex tracking info first thing this morning. I ended up paying $150 (with shipping) and have EVERYTHING plus some extras he threw in as well.

I KNOW you ended up paying a lot more, Tower should take them back.

As soon as mine arrive (Wed. I'm guessing) I'll let you know what I think...but I'm pretty sure that these were made for the Cermark F16...turbine, meaning they should easily handle the weight of our planes, as we won't be carrying liters of fuel.

opjose

Well look at this: http://www.ejf.com/index.php?main_pa...roducts_id=412

marktur

Wrong shape...I think I'll go hunt around RC Hobbies and Southeast Hobbies this weekend. I think a P-51 canopy might work... I'm sure I'll find something at one of the two shops - they're both HUGE shops...department store size...they stock everything!


IMPORTANT QUESTION:
Do I need to put in any left/right thrust when I mount the motor, or just straight on the thrustline?

I added about 3/16" ply to raise the motor...but I don't want to mount it until someone answers this one, as it will definitely affect it's flight.

Thanks,
Mark

lsu_fan

My Feedback: (43)

Guys I actually dremeled a "bowl" in the middle of the mount so my crankcase on my TH 75 would sit down in it and used the stock mounts.I didnt want to raise the motor because i didnt want to take a chance on the carb being higher than the pick up/tank.I also didnt want to raise the motor because I didnt want any unwanted prop wash over the horizontal/elevator.I did however uncover the mounts and saturate the heck out them with thin CA as well as the "bowl I dremeled.I have flown the crap out of mine,slow speed,high speed,inverted,high alpha on landings,knife edge,precision rolls(slow and point) and mine goes EXACTLY where I point it.The motor has never given me any trouble as far as going lean or rich in any position.Hope this helps!!

still4given

Hey Golfnut,

That is great news. I was really sad that I didn't get a chance to try more stuff with mine. I'm hopeful that I will get many more flights even though it's not as pretty anymore. The nose of mine bounced up and down all the way down the runway. It didn't dawn on me to to hold a little down elevator until it was up to speed. Too used to flying tail draggers.

Blessings, Terry

marktur

Hi Golfnut,
I wasn't sure if it was a good idea to dremel, so I now have my motor sitting about 3/16 higher than stock. Hopefully it won't make a difference. If it even hints of an issue, I guess I can add a 2-ounce header tank like my heli to be able to depend on constant pressure for the fuel...

Well see this weekend I hope.

I have to get longer mounting bolts tomorrow.

Did you use any left/right thrust in your motor, or not necessary?

Thanks,
Mark

lsu_fan

My Feedback: (43)

Marktur,
No left or right thrust.I forgot to mention that I mounted my tank facing foward with the lines "snaked" back to the motor.The way they call to mount the tank looks like trouble to me!
Jason

rastus21

Gday Marktur, you and me are on the same wavelength here, I also are building a retract version of the het f20, using Carls info, and yesterday received my bobcat....yeah! This bobcat is a hot looking machine for sure, may fly it this weekend, hopefully..... I'll use it for practise for the f20, cuz I've put a lot of work into the f20 so far.
Cant beleive how good the quality of the bobcat is, it looks like a much more expensive plane for sure, only paid $190.00 AU for it. Quite large to.

Anybody tell me a good prop for the 76???

Matt

still4given

Hi rastus,

I used an APC 11x7 and it seemed to fly it well. I will be getting a Graupner 11x8 when I get a chance. As I said earlier, I would add some glue to all of the formers and landing gear blocks that I could reach. when I endoed from about 20' up the whole servo mount came loose and broke both formers that were attached to it. I do not believe that would have happened if I had added some epoxy.

Blessings, Terry

MMallory

My Feedback: (1)

Terry,

Since this is a pusher, it shouldn't rotate until it has enough speed to fly. Just hold a little up and let her rip.

Mark

opjose

still4given:

Do you have the new "Retract ready" version?

My retract ready version came VERY well epoxied all around.

About the only place that I found which could stand a bit more epoxy was the area behind the rearmost former, that I could only access after cutting out the wing access holes in the fuselage.

Everything else had very thick beads of epoxy all around, more so than I usually see in ARFs.

Never-the-less I put even more epoxy down all over.

still4given

Yeah, well whether or not it should or shouldn't rotate, the nose wheel started bouncing off the ground after about the first three feet of roll. We have a dirt runway and there are a few small rocks. The bouncing didn't stop until it lifted off. I imagine the rear wheels are a bit close to the GC. Anyway. I would rather have to hold a little down elevator during roll-out than have it have a hard time rotating as I see in a few posts in this thread.


opjose

Yes this is the retract ready model. If yours is glued well then don't worry about it. Mine wasn't. One of the nose gear blocks was so loose I was able to remove it by just wiggling it. When I tried to put it back in, one of the formers came loose. I epoxied both formers and the blocks and I'm happy to say that that section survived the nose in just fine. Most of the damage to my fuse was caused by the servo tray and the two formers that it attached to coming loose. Both formers were busted up and as the servo tray moved around it busted up the gelcote where it hit. I believe if I had added some epoxy to them in the beginning the plane would have only had some scuffed paint.

Blessings, Terry