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Gas Powered Thoughts Advice for Gas Helicopter Success from Carey Shurley


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Old 11-27-2017, 06:29 PM   #21 (permalink)
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Is this model popular? Honestly surprised to see this being a gasser option. I've never seen or heard of a TSA heli till finding this thread.
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Old 11-27-2017, 07:54 PM   #22 (permalink)
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Unless the ball links were loose (which they should not be) there should be no difference, especially with an FBL machine. More likely it was just differences in the CG of the machines. There's no magical difference in linear movement that's passed though a bellcrank.
I have hard a lot of people say that but I can only go by what I have noticed. I swapped out my YS60 into a used furry that I got from here and now all 3 helis fly very similar.

My CG was perfect on the trex 600N.
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Old 11-27-2017, 08:41 PM   #23 (permalink)
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How does bell cranks behave with regards to stripping servo gears ? Where you can use sacrificial arms on DSC, does plastic discs do the same for bell cranks ?

Just curious.
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Old 11-28-2017, 07:17 AM   #24 (permalink)
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Metal arms are more viable on a bell crank machine. Generally youíll just have a link pop off and the servo will be fine. Not every crash, but most Iíve had on bell crank helis the servos have come through unharmed.
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Old 11-29-2017, 10:13 PM   #25 (permalink)
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Originally Posted by joecass2 View Post
I have hard a lot of people say that but I can only go by what I have noticed. I swapped out my YS60 into a used furry that I got from here and now all 3 helis fly very similar.

My CG was perfect on the trex 600N.
Rush 750 V1 has bellcranks and it's renown for being a very well flying machine.
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Old 11-29-2017, 10:24 PM   #26 (permalink)
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Metal arms are more viable on a bell crank machine. Generally youíll just have a link pop off and the servo will be fine. Not every crash, but most Iíve had on bell crank helis the servos have come through unharmed.
On a bellcrank machine I would be more inclined to use a simple nylon servo horn like the ones that come with most servos. The pushpull links equalize the load which means less chance of the arm flexing (it will never flex under normal load conditions) and it functions as a mechanical fuse.

I put my Rush 750 into a tree full speed reverse and it bent the mainshaft at a 45 degree angle, none of the servos were damaged. On the elevator servo one of the two pushpull links tore the arm of the plastic cross type servo horn it was attached to completely off with the ball still attached.
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Old 12-17-2017, 07:03 PM   #27 (permalink)
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Have the servo shaft supports also been eliminated? Those are actually pretty useful on an IC heli as they have the same effect as pushpull links (preventing soft mounted servos from rocking in the grommets) while allowing for a direct link to the swashplate.
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Old 12-18-2017, 09:40 AM   #28 (permalink)
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There are many gasser designs being flown by hundreds of pilots over 10s of thousands of flights that have direct to swash servos, and none of them have issues with servo rock causing adverse flight characteristics AFAIK.

Really, its a non issue.
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Old 12-18-2017, 11:54 AM   #29 (permalink)
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Originally Posted by jharkin View Post
There are many gasser designs being flown by hundreds of pilots over 10s of thousands of flights that have direct to swash servos, and none of them have issues with servo rock causing adverse flight characteristics AFAIK.

Really, its a non issue.
Maybe it's a West coast thing....
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Old 12-18-2017, 05:16 PM   #30 (permalink)
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Maybe it's a West coast thing....
Just because it's not absolutely necessary doesn't mean it's not a nice thing to have anyway. Soft mounted servos *will* move under load you have only to press on the swashplate to observe this.
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Old 12-21-2017, 07:05 AM   #31 (permalink)
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Just because it's not absolutely necessary doesn't mean it's not a nice thing to have anyway. Soft mounted servos *will* move under load you have only to press on the swashplate to observe this.
Hmm, you mnust have them all mounted sideways, or you are running the grommets way to loose.

With the servos oriented vertically (i.e. long dimension of the case parallel to linkage rod), I can push down on the swash hard enough to pop a link and the servos start screaming and the plastic arms start to flex, but the case doesn't visibly move.

I can shoot a short youtube tonight to prove it if you are in doubt.


And even if they do flex a faction of a mm, there is a lot of other slop in the system with less than brand new ball links , etc.... If Extrapilot where he he would likely give us a treatise on how none of this matters in flight once the system is loaded with flight forces.
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Old 12-21-2017, 10:07 PM   #32 (permalink)
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Well I have a TSA Infusion 700E right now that I got used at a good price and don't let the single sided slider on the TSA tail unit fool you it has less slop than the two sided slider on my Trex 550 and about the same as the JR style fork and ring slider on my Rush 750. They haven't upgraded to a two sided design because they don't need it. I haven't taken it apart yet but I suspect that the ball snaps into the plastic bellcrank like a ball link. The tail pitch mechanism is slightly draggy though it's a smooth "hydraulic" drag not a "sticky" drag. A setscrew collar is used on the right side of the tail rotor shaft (on the inside) rather than stepping it down from a larger diameter like on an Align tail rotor shaft.

Tail gears are 25T mod 1, the gears and shafts for the tail rotor and front TT drive are sold separately and fix to the shaft with a pin and setscrew in the end of the shaft. They also have a metal front TT drive gear though only the spur gear is aluminum and it seems to me that all it would do is wreck more expensive auto rotation gears.

Tail grips have zero lateral slop and only about 0.5mm of axial slop so very nice there. I like that the hub side bearing is a 6x12x4. The blade side bearings are a 5x10x4 radial and thrust bearings with the thust bearing in the center rather than on the end and the tail hub uses M4 nylock nuts instead of screws. The tail unit and grips comes in plastic and aluminum versions. I think if I were to trash the aluminum tail grips I'd probably just replace them with plastic. Likewise the "upgrade" ballraced tail pitch links probbaly aren't any better than the stock ones that use brass bushings.

They have an upgraded aluminum hub for the auto rotation gear (the stock version is all plastic). The plastic gear for this hub is different than the stock gear, it's like a smaller maingear that bolts onto the aluminum hub.

Tail mechanics on TSA helicopters are symmetrical, center is 0 degrees (with the belllcrank at 90 degrees) and they have the same maximum pitch in both directions.
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Old 12-22-2017, 06:36 AM   #33 (permalink)
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Here you go, hopefully this should remove any controversy about rubber mounting:

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Old 01-01-2018, 07:09 PM   #34 (permalink)
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Found out that if you use the "pro" tail links (plastic with brass bushings) with the aluminum tail grips and slider you need to put an M2x0.2 shim under the bushing on the tail grip side due to an alignment issue that causes the slider to become sticky toward the pitch limits. Seems that the ball bearing links are meant only for the aluminum grips and slider and the plastic ones with bushings are meant only for the plastic tail grips and slider.

Thing is though that the ball bearing links have a lot of sideways slop in them compared to the cheaper ones that use bushings.
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Old 01-01-2018, 07:16 PM   #35 (permalink)
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One thing that concerns me is the lack of a shim between the outer radial bearing and the thrust bearing (which is in the center). In this configuration there is usually a 5x7 shim in between the bearings to prevent the outer race of the radial bearing from contacting the thrust bearing (with this configuration the load passes through the center of the radial bearing to the thrust bearing so they use a shim that matches the ID of the radial bearing)

Checking inside the tail grips on the 700e revealed that it's not an omission in the manual, there really isn't a shim there and testing with the two bearings on a 5mm shaft seems to indicate that the bearing outer race actually does touch the thrust bearing. I suppose you could fix it by putting a 5x7x1 shim in between the bearings and using a 5x10x3 radial bearing in place of the 5x10x4.
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Old 01-02-2018, 05:47 PM   #36 (permalink)
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The head has a spindle teeter hub like the Synergy 766 and the Gaui X7 Formula heads that prevents spindle lag. In this case they have used POM bearings instead of ball bearings on either side of the head to support the teeter hub. I actually like this, a ball bearings are really unnecessary here and the POM bearings are more durable. There is also an oblong plastic piece behind the dampers that seems intended to prevent the spindle from hitting the aluminum inside the hub.

The grips had a bit of side to side play in them, less than 0.5mm but it was definitely there. It seems they designed it with no preload, this bothered me so I added a 10x12x0.1 shim between the damper spacers and the blade grip bearings and it tightened up the head without introducing any drag into the grips. It should also be noted that the stock dampers are very soft (50 durometer) and it may be that this lack of preload may not have existed with brand new dampers and bearings. I did change out the bearings with new AVID ones and the play seemed to be slightly less with the new bearings. It might also not be a problem with the harder dampers. Regardless if it bothers you it's simple to fix.

I actually think I prefer this to how some helis have super tight heads with a lot of preload. This way you can fine tune it so that the head is tight but the grips don't start to drag.
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Old 01-03-2018, 07:23 AM   #37 (permalink)
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I love how you completely ignore the fact I answered your question about slop in rubber mounted servos, and just move on to dissecting something else in the design.

Its almost like you are having a separate discussion with yourself........
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Old 01-03-2018, 08:29 PM   #38 (permalink)
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Quote:
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I love how you completely ignore the fact I answered your question about slop in rubber mounted servos, and just move on to dissecting something else in the design.

Its almost like you are having a separate discussion with yourself........
Dunno why you take this so personally but whatever...
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Old 01-03-2018, 08:41 PM   #39 (permalink)
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The M2 cap heads used here and there on this model are not stock M2 screws, they are special small diameter head Allen screws. These are used for the M2 linkage balls (they are two part balls like the old Thunder Tiger ones) and the screws that hold the two halves of the auto rotation hub together. You cannot use stock M2 cap head screws in place of these. Especially with the auto rotation hub the side of the head would bite into the side of the hub at the bottom (the chamfer near the screw holes) if you used a stock screw. TSA also doesn't seem to sell these screws separately, if you ever need to replace them you will need to track down some suitable screws.

Axial brand m3x8 and m3x14 self tapping button head screws look like a suitable replacement for the self tapping screws. As far as I know they don't sell those except with spare parts either. Or at least there was no hardware kit listed in the spare parts list in the manual.

Synergy M3 dress washers look like an exact match for the TSA dress washers (again, not sold separately)

EDIT: I wasn't aware of this but there are actually two different auto rotation hubs, one which uses a sprag clutch ($90) and two radial bearings and a less expensive version ($38) which uses a one way bearing and two 16x23x2.6 brass bushings in place of the radial bearings. The sprag comes with the Platinum kits and the cheaper one comes with the "Pro" kits (which also have fiberglass frame sides, plastic bearing blocks, plastic main and tail grips and a plastic motor mount and a plastic tail case. The cheaper hub also doesn't have the custom M2 screws either, it's a single piece hub with the one way bearing and the upper brass bushing pressed in. The lower bushing can rotate freely inside it's seat and it'd probably be a good idea to use some green locktite to fix it in place so that it rotates on the steel sleeve rather than rotates inside the housing as this would wear down the aluminum over time. The steel sleeve is just as solid inside the hub as with the sprag version (i.e. no side to side slop) however it does rotate with a little bit more drag so it's possible you may get a few seconds less hang time in auto rotations with this hub.

Replacing the one way bearing in the less expensive housing looks like it will require a blind hole bearing puller. I have used that method to replace the clutch in the Rush 750 auto rotation hub. It looks like there is plenty of room between the top of the clutch and the brass spacer for the flange to catch it so that it could be pressed out of the hub.

Last edited by Atomic Skull; 01-05-2018 at 05:44 PM..
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Old 01-31-2018, 05:49 PM   #40 (permalink)
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After dealing with the Infusion 700E elevator arm I have to say I agree with removing it. It's a fiddly design and getting it working smoothly was a pain in the rear. Though if you don't care about scratchy bearings or having the assembly move with no drag it might not be as big of a deal to some people.

The main problems with the elevator arm design are undersized bearings and inconsistent thickness of the CF side pieces. The bearings are 3x6x2.5 with a 0.6mm flange and the CF side pieces range from 1.85-2.10mm CF (not within the same piece but from piece to piece) and because the bearings are inserted with the flange on the outside you can end up with an excessive side load on the bearings if the CF is much thicker than 1.9mm. In addition I feel that the 3x6x2.5 bearing are undersized, the typical static load rating for that size bearing is around 12 lbs. They should have used 3x8x3 flange bearings inserted from the inside rather than the outside (so that the thickness of the CF would not matter) or just used a traditional elevator A-arm with a ball link at the top.
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