Some pics of my custom TRex-450 based AP bird.

[skeletor]

the weather has been horrible (for california :lol:) so I finally finished work on the custom 450 this weekend, after quite a lot of testing and one slight setback costing me a set of blades I think it is done.

anyway, it's based on the HDX-450 frame running 4S with a Medusa 28-40-2500 motor on a 10t pinion and Jazz 40-6-18 ESC.. the motor sticks out the bottom of the frame and the wires exit at the bottom of the motor so there wasn't any good way to attach the Askman mount.. I had a spare set of LG laying around and with some rubber gromets they fit perfectly.

head is microheli, HDX flybar cage and levers, Align washout block, microheli swash.. Hitec Fusion 9 RX, 401 & 9650 on the tail.. the boom is all custom 440mm with the new align metal tail stuff. main blades are MS comp 395's..

the graph shows a couple of short hovers with the new gear on, avg around 12-13A for a hover is ok although there was no camera on board and this was running a set of tech-mp.com 335 blades at 2400rpm. I plan on about 2000 rpm with the 395 blades.

rich.

[Tonystott]

Now that is different!

395 blades??? Aren't you going to run into tail rotor clearance issues?

Also, wouldn't there be less pendulum effect if you just added some spacers? I am thinking of (say) 1 inch long thick walled aluminium tubing that M3 bolts could thread into... Just a thought.

[skeletor]

I didn't notice any pendulum effect when I tested it the other day, but that was without the camera so it might. Spacers would deffinately be an option if that happens, I pretty much just used what I had on hand.. I'll try and get out tomorrow if the wind is ok and test it out with the camera on board.

the boom is almost 90mm longer than the stock Align boom so there are no clearance issues.

rich (sitting in cali listening to Triple J :) )

[MicroMan]

Thats a nice looking AP setup youve got there,

[oscillator]

Great idea. So what belt are you using to work with the longer boom?

The biggest problem with a Trex450 AP ship is the 450 is hard to Auto even without a load. If you ever have a forced auto with the camera on board (esp if you were in a hover up high) it isn't going to be pretty. I wonder how much longer blades will correct this problem...

[Tonystott]

I didn't notice any pendulum effect when I tested it the other day, but that was without the camera so it might. Spacers would deffinately be an option if that happens, I pretty much just used what I had on hand.. I'll try and get out tomorrow if the wind is ok and test it out with the camera on board.

the boom is almost 90mm longer than the stock Align boom so there are no clearance issues.

rich (sitting in cali listening to Triple J :) )
We we first flew my Trex AP ship, the camera weight really moved the heli around, until I stiffened up the damping of the camera mount gimbal (closed cell foam).

[skeletor]

Thats a nice looking AP setup youve got there,
thanks MicroMan, it's a toy compared to what most ppl here have but I am enjoying it anyway :D

We we first flew my Trex AP ship, the camera weight really moved the heli around, until I stiffened up the damping of the camera mount gimbal (closed cell foam).
how heavy is your camera ? I have a Samsung A402 which is around 110g and a Kodak V570 at 145g.

I tried all sorts of foam combinations and could never get it just right so I got a couple of RC car shocks from the LHS and fitted them to the gimbal.. The shocks allow preloading on the springs so it didn't get the pendulum effect when it was on my stock SE. I only have 2 shocks on there but it seems to work much better than the foam ever did. you can see the front shock in the close up shot above.

rich.

[skeletor]

Great idea. So what belt are you using to work with the longer boom?

The biggest problem with a Trex450 AP ship is the 450 is hard to Auto even without a load. If you ever have a forced auto with the camera on board (esp if you were in a hover up high) it isn't going to be pretty. I wonder how much longer blades will correct this problem...
The belt came from mcmaster-carr.com part# 1679 K681:

Trapezoidal Tooth Urethane Timing Belt .080" Pitch, Trade Sz 385Mxl, 38.5" Outer Circle, 1/8" W

I pretty much ordered a couple of these belts and then made the boom to suit the belt length out of some stock thin walled 12mm AL tube.

this pic gives you some idea of the blade difference (44mm wide vs 31mm wide) - the red ones are 335mm tech-mp.com blades. the 395's weigh in at 42g each and hold a lot more energy than the stock blades.

rich.

[Tonystott]

Thats a nice looking AP setup youve got there,
thanks MicroMan, it's a toy compared to what most ppl here have but I am enjoying it anyway :D

We we first flew my Trex AP ship, the camera weight really moved the heli around, until I stiffened up the damping of the camera mount gimbal (closed cell foam).
how heavy is your camera ? I have a Samsung A402 which is around 110g and a Kodak V570 at 145g.

I tried all sorts of foam combinations and could never get it just right so I got a couple of RC car shocks from the LHS and fitted them to the gimbal.. The shocks allow preloading on the springs so it didn't get the pendulum effect when it was on my stock SE. I only have 2 shocks on there but it seems to work much better than the foam ever did. you can see the front shock in the close up shot above.

rich.Rich, my camera is a pig at 160g. I didn't notice the oil shocks, forget everything I said about damping. You are right, the foam is a poor substitute for doing it properly like you have done.

[skeletor]

oh well, I took it out to fly and some people who shall remain nameless laughed at the landing gear legs.. so I got to thinking about what Tonyscott said and this is the result. it looks much better now.

rich.

[MLaBoyteaux]

I'm sure the legs were just as functional, but it does look a lot better :D

[GGoodrum]

Yep, it does look better. :D

This is actually a nice idea, doing a stretch and running 395s. I have a bunch of these sitting around. Maybe I'll do a stretch on an e325 Mini-Titan. :)

-- Gary

[aramsdell]

This is my landing gear for camera http://runryder.com/helicopter/gallery/45894/
The camera mount has changed slightly but the gear has only had 1/2" pipe insulation added to it. The legs are tail booms from crashed Blade CP's. the actual mount to the Heli's frame is soft sheet aluminum that I cut out with dremel shop. There is a 90 degree bend at top and (2) 2mm hex head botls hold it to the original LG attachment holes both front and back. The legs are held by tabs on the aluminum piece that are bent around the CF legs to a crimp fit. I fly a 9.2 oz camera with this no problem. I don't think it'll auto though at that weight.

[Tonystott]

Rich,
that stretch looks like the go to me! My only concern would be loads on the mainshaft and feathering shaft, but doing a strtch version for AP makes just as much sense for the little buggers as it does with bigger ones.

I think I will go the same route. Have you tried a practice auto at height yet?

[Longwing]

That is a great looking AP ship. I keep us posted on the results. I am very interested in your set up. Thanks for sharing

Blake.

[bat1]

what type of batteries are you using and what type of flight times?
Also what is the total weight with camera attached. Stretching is a good idea but I am concerned about what upgrades would be needed for the power system.

I am working on making my own composite blades and may be able to cut down the weight and change the dimensions of of the blades a bit to decrease amp draw.

[Tonystott]

what type of batteries are you using and what type of flight times?
Also what is the total weight with camera attached. Stretching is a good idea but I am concerned about what upgrades would be needed for the power system.

I am working on making my own composite blades and may be able to cut down the weight and change the dimensions of of the blades a bit to decrease amp draw.
Tommy, I can see this leading to a really useful AP Trex! Your plans to peel off weight, in combination with a stretched boom plus possibly longer composite flat bottoms could result in the nirvana for AP Trex flying -

autorotation capability!

395 blades would provide a 35% in disc area (I have assumed the same chord, but lift would increase further with a wider chord) while outwards force at the grips would increase 10% at 2200 (assuming the same blade weight)

Of course, battery would probably need to move to 4S, but this is very interesting indeed!

[bat1]

I have never autoed in my life so I would not know where to begin of course I have never flown a heli at a time where I both had aquired basic hovering skills, and or the heli was light enough to auto. Ap trex has always been a pig. Since I do not want to hijack this thread. I have some new Ideas about custom blade design for an AP TREX which I have running on another forum. for those interested the discussion is here
http://www.rcgroups.com/forums/showpost.php?p=6739078&postcount=32

[Tonystott]

Sorry I missed that thread. I'm there with bells on! :D

[skeletor]

Rich,
that stretch looks like the go to me! My only concern would be loads on the mainshaft and feathering shaft, but doing a strtch version for AP makes just as much sense for the little buggers as it does with bigger ones.

I think I will go the same route. Have you tried a practice auto at height yet?
no auto's yet, I'm just trying to break it in without breaking it. :) ESC is a Jazz with softstart so not sure if I can try auto's up high and get the motor spooled back up before impacting mother earth. I've tried a couple down low and the blades hold a lot of energy..

I went with the microHeli head and grips because the grips have thrust bearings and the feathering shaft is larger than the stock one. so far the main shafts seem to be holding up ok. I do have some problem with the head block at the moment which is causing all my pics to turn out fuzzy. I have replace the main shaft twice and I still have a very slight high speed vibration in the head. I think the head block may be tweaked, I need to get some time to work on it.

I just picked up a set of 385 blades, they were slightly cheaper than the 395's so I will continue testing with these. Flat bottom blades would be cool, I would be more than happy to test some.

I haven't done real flight time testing but it only draws 12 - 13amps in a hover, (4S packs), all my flights have been short. I also don't have the AUW and I no longer have a scale, will find out next weekend tho.

it flys very stable, more so than the standard 450SE I have.

rich.

[Tonystott]

Don't worry too much about having thrust bearings in the head (obviously beefier feathering shaft would be forth the price of admission alone:)). I recently visited UAV Vision (they make mega$$$ UAV turbine helis) and Mike Bailey looked up his bearing book, which showed that while a thrust bearing could take 10-12 times the side loads compared to a normal bearing, the side loads the latter could take were way in excess of the forces available anyway, at least in Trex sizes.

As regards the Jazz softstart, you could always cheat a bit with practice autos by setting the bottom of throttle in throttle hold to tick-over rather than fullstop.