Changing 600Pro Tail Gear Ratio

[OnTheSnap]

For more info on why this important, please see the original tail blow out thread here:http://www.helifreak.com/showthread.php?t=315856

Credit to Black Titanium for spotting this gem first.

As many new owners of the 600 Pro know, Align unfortunately dropped the tail gear ratio on the Pro from 4.5 (all other 600 class machines) to 3.85. The logic behind this move is to allow for extreme RPMs on the head, >2400. the problem is even the top Pro's flying 600's in competition run 2250 max doing the most demanding 3D routines on earth. So the standard hack that wants decent tail authority at world class headspeeds of 2250 has to run 105mm tail blades. There are nothing but downsides to running 2500. Less flight time, much harder on the Heli components, blade failure, etc.

Also note that Align always gears for no governor. But in this case we are over geared just enough to run 2200-2350 gov'd. So in fact the gear ratio is "perfect" for the governor fans among us.

Well it turns out Align snuck in a poorly described part in May that fits the deeper one way bearing of the pro but keeps the old mod .6 tooth count and works with the old tail drive gear.

Parts:

http://grandrc.com/p7255/H60121-Torque-Tube-Front-Drive-Gear-Set/product_info.html
http://www.align.com.tw/shop/advanced_search_result.php?keywords=H60020A&osCsid=14b3d9ded83937147f0a99a10f30d89f&x=43&y=14

I bought one at : http://www.experiencerc.com/store/h60020t_autorotation_tail_drive_gear_t-rex-p-8897.html

You need both the new auto gear and one of the older tail drive gears. Both linked above.

I've actually installed the new gear already on my 550 and can confirm it fits the 600 Pro OWB, and has the old mod .6 tooth count.

Pros:
Lets you run 95mm tail blades
2250 gets you the same tail holding power as 2500 on a stock setup

Cons:
Increases vibration since the TT runs 15% faster
Auto gear is mod .6 instead of mod .8. So not as strong


For me personally I will stick with the 105's since the vibration reduction is worth it.

[backburner1955]

That second Align Link goes to a Taiwan only site that wants you to log in, can you link to something state side that we can order from?

[Commodore8888]

Just ordered one from AlignTrexParts.com

They usually have the hard to find stuff being that they literally walk over to the align warehouse in CA to pick things up. Also great CS.



http://www.aligntrexstore.com/Autorotation-Tail-Drive-Gear-set-H60020A-_p_485.html

Front TT gear is the same old 550/600 20t that some folks already have lying around. They have them if you don't.

Grand RC might have the stuff too. Haven't checked.

[microhelijon]

Hi Snap,

with the 105 tail blade with the rest stock,
can I run as low as 1900-2000rpm on the FBL

[OnTheSnap]

Hi Snap,

with the 105 tail blade with the rest stock,
can I run as low as 1900-2000rpm on the FBL

Works as well as any 600 machine. Just make sure your ESC doesn't overheat.

As far as links go for the auto gear, the part is still scarce. Hopefully that changes in the next few weeks.

[Laddy]

On The Snap, thanks for doing the test for us.

[backburner1955]

Thanks for all of the info OTS, can you post comparison pics for those of us that want to do the change... Thanks again.

[rotaryguy]

For me personally I will stick with the 105's since the vibration reduction is worth it.

I went with 105's as well and this option far outweighs the potential vibration penalty for upping the tail rotor speed with the alternate gearing.

[matchbox]

Hey OTS, about the issue with vibration at higher tail speeds. I am not sure how many of you have notice that all the Align TT's have only one of the four spline points that spin the TT in the centre of the tail boom.
This might be hard to explain.
1) place the boom into the front tail clamp
2) then insert the torque tube in from the open end
3) push the TT spline into the gear spline
4) Now move the auto-rotation gear to make the TT spin in the boom
5) unless your lucky and got it right the first time, you will notice the TT spins off center
6) If it does, pull the TT out a little and turn it 90 degs and push it into the next spline.
then spin it again to see if it is more on centre.

If you try all 4 spline points you will notice only one spins true to center. Once the front spline is done you will have to make a mark on the gear and TT, then do the rear gear as well.
This slight offset on the TT splines can cause excess vibration and power loss at high tail speeds. Its a bit of messing around, but it all helps performance.

[OnTheSnap]

Hey OTS, about the issue with vibration at higher tail speeds. I am not sure how many of you have notice that all the Align TT's have only one of the four spline points that spin the TT in the centre of the tail boom.
This might be hard to explain.
1) place the boom into the front tail clamp
2) then insert the torque tube in from the open end
3) push the TT spline into the gear spline
4) Now move the auto-rotation gear to make the TT spin in the boom
5) unless your lucky and got it right the first time, you will notice the TT spins off center
6) If it does, pull the TT out a little and turn it 90 degs and push it into the next spline.
then spin it again to see if it is more on centre.

If you try all 4 spline points you will notice only one spins true to center. Once the front spline is done you will have to make a mark on the gear and TT, then do the rear gear as well.
This slight offset on the TT splines can cause excess vibration and power loss at high tail speeds. Its a bit of messing around, but it all helps performance.

Holy smokes! If this is true Align has made a huge mess of their torque tubes!

My intuition disagrees with this idea. Looking at how the TT mates with the umbrella gear, I just can't see how there is any asymmetries. ?!

And of course nothing like this is mentioned in any Align manual AFAIK?!

[matchbox]

I'v been setting my torque tubed Align helis up like this from the days of the first 600e and they are still like it.
I think the issues comes from the Delrin plastic gear spline in the gear and not the machined spline on the TT itself. Delrin is a very hard plastic and when it cools in the die there can be shrinkage of the part in different areas. This could cause the the slight offset. Remember that it only takes a small offset in the plastic gear spline at the front end to throw the rear end out by heaps, due to the length of the tube.
Check out your TT helis for yourself !

[cb3d]

So Snap, Did you witness an increase in vibration personally or are you simply stating that this is a possibility? Great job again on this issue.

[davehour]

Hi:

I've found when the torque tube bearing is glued with CA to the torque tube, the bearing can stick off center or not perpendicular to the torque tube due to the play between the torque tube and bearing inner race diameter.

It's easy to check if the ball bearing is not right in the torque tube: When the rubber cover is installed over the bearing, or even without it, as the torque tube is rotated, rubber cover or bearing will be moving or "dancing" depending how off the bearing is on the torque tube. This in fact, will generate a lot of vibrations. In addition, this could be one reason why the torque tube doesn't run true after it's installed in the boom.

I found peculiarity when I installed the ball bearing of my 600 Pro. What I did to fix it was to force the bearing until it was perpendicular to the torque tube, and the rubber cover didn't move anymore. So summing up, the bearing should be glued with a little amount of CA so you can rectify it in case it doesn't stay true while the CA sets. Then, it will be possible to correct the bearing on the torque tube, and after it's right, more CA could be applied to secure it in place.

David

[OnTheSnap]

So Snap, Did you witness an increase in vibration personally or are you simply stating that this is a possibility? Great job again on this issue.

Thanks! It's just speculation based on experience. I didn't do any formal testing with the vbar spectrum analyzer to confirm it.

With the sensor mounted in the front of the heli on the Pro, I doubt it would be a major issue anyway. But spinning the entire assembly 15% slower should have some benefit with the vibrations. Who knows, it could be worse depending on resonant frequencies, etc.

[Commodore8888]

Just ran it with the higher tail ratio. No substantial vibe increases however anyone with even small vibe issues will see a noticable increase in tail vibration. Nothing that wont affect a well setup machine though or be outside of the scope of normal vibrations.


Other than that...I dare anyone to try blowing it out with 105's and that ratio. Tried even at 2k and below headspeed for funzies. No dice :bacon

[OnTheSnap]

Careful. A 4.5 gear ratio and 105's may over stress the tail gear design and strip them in flight. You're at 700e loads now, without the beefy 700e tail gears.

[Commodore8888]

If I go to run 2.1k+ headspeeds I'll drop down back to stock gears or 105mm blades only. Curious if there are stronger gears that will fit in that tailcase.

[Helico-pteron]

Even at 2500 HS the tail will blow out during fast tail in maneuvers.

Happened today and that was the fastest I have had it tail in since I bought it. I agree with the OP that 105 tails is the best option here.

[OnTheSnap]

Even at 2500 HS the tail will blow out during fast tail in maneuvers.

Happened today and that was the fastest I have had it tail in since I bought it. I agree with the OP that 105 tails is the best option here.

Very surprised to hear that you could get it to blow out at 2500 with 95mm.

If you decide to go with 105's I'd be cautious about going faster than 2300. I'd be concerned that you could overload the umbrella gears.

[Helico-pteron]

No plans to switch up to 105 until I get my gearing sorted. Even then I mat stay with 95, I just dont fly that extreme.

[matchbox]

Do you guys that are using the 105 blades, finding that you have to be a little more carefull on auto's, so as not to touch the tail blades on the ground and risk braking the front gears.

[Helico-pteron]

Do you guys that are using the 105 blades, finding that you have to be a little more carefull on auto's, so as not to touch the tail blades on the ground and risk braking the front gears.

If you want the heli to sit higher, replace the landing struts with standard 700 struts instead of the 700 FC3 struts the kit comes with.

[matchbox]

Na, i want to keep it as low as stock. I just ment the 105mm tail blade sits as low as the vertical fin and touchs the ground if we are not carefull when landing.

[Helico-pteron]

Na, i want to keep it as low as stock. I just ment the 105mm tail blade sits as low as the vertical fin and touchs the ground if we are not carefull when landing.

Put a 700 fin on then...

[matchbox]

Thats another option! Might have to order one.