Ali's build thread

[alilee]

Originally Posted by Groucho_

These fit:

http://www.fast-lad.co.uk/store/mik4...mm-p-5458.html

So no concerns about getting the single-arm servo arms sitting orthogonal to the servo?

If I understand this, it would show up as swash-levelling adjustments inside VBar (if I keep the three links at equal length and there isn't any variation in the servo mounting positions on the frame), and some travel adjustments to level the swash at collective extents..

They look nice and I can get them from my LHS so I'll get them to compare.

Originally Posted by Mercuriell

Not sure if you're gonna get in the green range on vbar with those shorter arms.

The manual suggests 16-18mm so 16.25mm is inside the spec. Again, if I understand this, it will be harder to get high pitch in the green range, but perhaps I'll get 10-12 deg. at 100 for collective which should be fine given my ability and target airspeed. I'll definitely report back.

I'll measure the Mikado ones above and show their numbers back here too.

[CyprusFlyer]

Originally Posted by Mercuriell

Look interesting - I like the FutabavT arms as they are soft and strip the spline rather than the servo gear in event of a blade strike. Not sure if you're gonna get in the green range on vbar with those shorter arms.

PS Also like the Mikado glass filled plastic arms Groucho linked to, these are used on the Exxtreme

+1 on that, had a mishap a while ago and the splines shredded in the servo arm hub, easy and cheap to replace those arms. Also you can see which of the 3 arms line up and cut the others off, close enough and minimum correction required on the Vbar (Trim setup).
IMO stock Futabo arms are very good for the TDR.

[Groucho_]

Originally Posted by alilee

So no concerns about getting the single-arm servo arms sitting orthogonal to the servo?

If I understand this, it would show up as swash-levelling adjustments inside VBar (if I keep the three links at equal length and there isn't any variation in the servo mounting positions on the frame), and some travel adjustments to level the swash at collective extents..

They look nice and I can get them from my LHS so I'll get them to compare.

The concern for arms not being at 90 degrees are there for all servo and arm combinations...

You adjust for this with your TX in a flybarred heli normally, and with your FBL controller in a flybarless heli...

I normally get an extra pack or two of servo arms, to have more chance of getting them all as close as possible to 90, therefore necessitating the least amount of correction.

On the TDR, although I got those mikado carbon fibre arms to which I linked, I ended up using the stock Futaba servo arms.

[alilee]

Originally Posted by Groucho_

as close as possible to 90...using the stock Futaba servo arms.

So I blooded three attachments on the rotary tool, and cut, ground and cleaned the Futaba arms. I also took delivery of the Mikado arms, and they are nice arms - small and hard. In fact, I question whether the splines will fail more like plastic or aluminium.. They seem to line up well with the neutral position on my servos pretty well (but not quite perfectly matched like the Futaba ones).

In terms of geometry, the manual says 17.5mm radius is optimal, but the best hole in each differs quite a bit:

Futaba: 18.4mm
Mikado: 16.75mm
Du-Bro: 16.0mm

So I think I'm going with the Mikado ones for now based on the smaller throw and yield some pitch at the extremes. Thanks everybody.

[donskills]

I use the Mikado arms and got what I thought is a 2perfect" set up!! My TDR has flown amazingly from the first hover!!

[alilee]

Progress is slow I know - not feeling confident enough to rush ahead..

I've put the servos in, but I'm not sure my eyeballing positioned the link from the elevator servo close enough to vertical. It's threadlocked in, so I'm going to live with it for now. Any tricks if I decide to have another crack at it?

Also, assembling the motor I put the 0.5mm spacer between the pinion and the 700-52 motor and a couple of 0.2mm spacers between the counter bearing at the end of the pinion per the manual. Those spacers rattle around there as the pinion is nowhere near the counter bearing (see picture). The counter bearing support and motor fastening plate are tight against the motor.

I'm going to add the 1.0mm spacer to move the pinion down away from the motor but I don't think that will completely bridge the gap leaving the two 0.2mm spacers mobile but I think it will move the pinion into better alignment with the intermediate gear. Shall I just remove those two spacers and run with the pinion floating? Thanks for any advice..

[CyprusFlyer]

Something is wrong there, way out, have you mounted in the frames to see how it aligns with the gear?
The biggest gap on mine is between the pinion and motor, undo the grub screw and see how it lines up when mounted.

May be some differences of opinion (again) ref pinion shims, IMO just add shims on the bottom to get the pinion level with the gear, only tighten the grub screw when:

You have the pinion level with correct no of shims and
the motor mounting bolts are in finally tight.

That way there are no loads on the motor bearings and the counter bearing prevents any downward force as well as axial movement. Thats all I done, 45-50 flights and all is still well!

[alilee]

I haven't soldered anything yet but having the engine in position has afforded the opportunity to see how cabling might go.

In this picture, the ESC inputs feed under the motor counter bearing and fold under the ESC plate, trying to keep clear of the crown gear, and run under the zip-tied plate to the power switch. The switch input cables come out the front for easy connection to the battery.

There is not much (2-4mm) clearance between the battery and the switch. Even though there is space in between the zip-tie cross bars, the cables enter and exit the switch on the same plane making it hard to mount it up in there (it's not mounted in the picture - just resting on the battery). I'm not sure if the switch accumulates heat.

The cables between the motor and the ESC are very neat and the signal line comes out of the ESC further aft which means there will be more play for routing that cable too.

I'd be happy with this if I can make it work..

[ZuvieleTeile]

Originally Posted by alilee

Progress is slow I know - not feeling confident enough to rush ahead..
I've put the servos in, but I'm not sure my eyeballing positioned the link from the elevator servo close enough to vertical. It's threadlocked in, so I'm going to live with it for now. Any tricks if I decide to have another crack at it?

It was hard to see for me too, so I went with "feeling".
I fire the system up and feel, if the black plastic tube around the elevator rod is still nicely rolling. The same with full pitch/elevator and the same on the negative side.
If it gets stuck somewhere or is hard to roll, then there has to be some adjustment of the servo.

As for the power switch and associated cables.
I made myself a longer ESC plate and mounted the switch underneath the plate.
There is about 51 mm space between the switch and battery tray bars.
Looks almost like yours.

[alilee]

Originally Posted by CyprusFlyer

...how it aligns with the gear? The biggest gap on mine is between the pinion and motor...

Thanks - your post has encouraged me to study the manually much more closely. I believe the intent is to pack the gap between the pinion and the motor so that it aligns with the intermediate gear. On mine that will be a 1mm and a 0.2mm spacer. This deviates from the exact language of the manual which states that a 0.5mm spacer must be used.

The manual notes on p.23 that between the pinion and the counter bearing there should be a gap of 0.1-0.2mm "so that there is no axial pressure onto the counter bearing" so a 0.2mm and 0.3mm spacer go there.

Now, it fits perfectly.

[alilee]

Originally Posted by ZuvieleTeile

...if the black plastic tube around the elevator rod is still nicely rolling.

My plastic tube is not really mobile as it is under pressure from the ball links. Does it need to be mobile? This might work itself out when I change the length while levelling the swash.

[Mercuriell]

There's been a couple of reports of elevator linkage breakage associated with loose sleeves, but I wouldnt want to preload the links though, snug but not tight IMHO

[alilee]

Originally Posted by ZuvieleTeile

...for the power switch... I made myself a longer ESC plate

Thanks very much for the pictures - illuminating. I see you mount the aluminium cover upwards (rather than the PCB) which means the wires flow better over the studs.

I'm not up for crafting a plate, but I can see the benefits of your tailored notches and holes (btw, I also know about the CR-Modelltechnik plate). At this stage I'm expecting the switch will mount fine inverted under the standard plate (with shortened wires to the ESC) except that the switch and ESC will be back-to-back and heat may build up in the plate. Is this one of the main reasons for your custom plate?

[alilee]

I'm happy with my tail. Interesting it turns the tail clockwise on a right-hand implementation unlike say, a Squirrel. What production helicopters are like that?

Three points to note:

• I struggled to get the final 0.2mm washer between the spacer and the bearing opposite the gear and in the end left it out so there is a tiny bit of axial play inside the gear. I could have used a second 0.1mm washer.
• I think I threaded either the nut or screw fastening the threaded link-ball on the bell crank. It is being held there by thread-lock.
• I filed down that same screw to ensure clearance above the boom, and it sits perfectly so I only used one of the spacers (939e) on the bell crank.

Any of these likely to bring down the ship?

[Mercuriell]

That bit of axial play not an issue, better than preloading radial bearings - dont like the sound of stripped threads on a vital link like tail control - threadlock not adequate to secure a stripped thread, disassemble, check it out and replace if necessary!

That rotation of the tail with the downwash gives the TDR much of its distinctive sound

[alilee]

So I know for over the last three months of the build this helicopter has pretty much made me its prison lover.

Two challenges have been taunting me on a daily basis - first, soldering the banana connectors between the motor and the ESC and the SPS switch; second, drilling the hole for the SPS switch in the skid plate.

One of the main reasons I have embraced Anderson Power Poles is so I wouldn't have to solder (and for me that means learn to solder). I flirted with the idea of APP's between the switch and the ESC but because that would not work for the motor, I got a bit paralyzed for a while. Eventually I ran into a guy (Aiden - thanks!) who works for a LHS (ArkRC) in another city who I immediately trusted to do the soldering for me. I sent the box of parts, but happened to be travelling so I got to see him do it and bought some knick-knacks while I was there. The charge was nominal but the peace of mind was sublime.

I have the Dremel, but without a press I didn't like my chances drilling the plate accurately and neatly (SPS switch requires a 16m hole, plus six screw holes around the big one). Plus I didn't really want to risk breathing in or leaving any carcinogenic CF dust around. The soldering energised me, and I eventually found an automotive engine shop willing to do the task. Unfortunately they sat on it for a week or so and then declared they were too busy.. but I found another one who promptly did a pretty good job on their high-speed drill press or milling machine. Their minimum labour charge was severe (I should have organised myself to do half a dozen).

Obviously I'd preferred to have done these things myself on my model but I am actually pretty happy with the outcome, and don't think about the shame very much at all now...

[CyprusFlyer]

Glad you got the soldering done, those Power Poles are not up to the task IMO, hada few friends swear by them but all change when they went into melt down on a Logo helicopter, I do not think they are gold plated either which means corrosion/tarnishing sets in quick.
I recently cut a hole in CF plate for the SPS switch, just drilled small holes cut out with a special junior hacksaw blade for CF, then a metal file works nice on CF, just have a vacuum cleaner going to suck up the dust! Another mod I did was to solder the ESC wires direct onto the SPS but not really necessary.

[Groucho_]

Originally Posted by alilee

Plus I didn't really want to risk breathing in or leaving any carcinogenic CF dust around.

CF dust is carcinogenic?!

[jhunter]

No it's not. Myth. I'm not saying you should try and breath it but its not carcinogenic

[desertstalker]

Originally Posted by Groucho_

CF dust is carcinogenic?!

If the particles are fine enough and are inhaled deeply enough. A bit like fibreglass, no where near in the same league as asbestos (though they do work via similar mechanisms).

If you do a lot of work with CF wear a mask and use water to keep the dust down. Washing it away (of the floor or whatever) is sufficient to clean up really. Small quantities are not really an issue (you are probably at bigger risk from cancer from eating bacon )