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Old Jan 27, 2013, 05:31 AM
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fg1972's Avatar
Australia, Melbourne
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Front retract is a real pain in the A..
I've spent many hours looking, thinking, trial and error and have come up with this. Wheel closes forwards and I've added a couple of locating pins to straighten the strut as it closes. Now the next challenge is to get it inside the fuse without too much hacking.
By the way, I've put on a slighter smaller front wheel and if all goes well it should retract flush or close enough with the fuse.
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Old Jan 27, 2013, 08:52 PM
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It can be difficult to set up right but....
If your incoming pushrod to the steering rod slider is rigid at its incoming height, the that will automatically make the leg go to straight as it folds up.
This is because (if you did all positions correct) it is then like a fixed horizontal rod, and the steering rod slider must also stay at that given height. That means the steering rod must be (eg in yours) just below the pushrod height - just the distance of the slider/clevis hole to hole. If the correct height - it stays straight. If too low...it goes a bit 'left', a bit high goes 'right' (or those in vice-versa), as it folds in.

If a servo is mounted ahead of the folding leg, then all this stuff goes BELOW the bush (not above as in yours), but the end results are all the same.

When a servo is very close, like yours, you possibly lose ability to control that pushrod to be rigidly level. eg, if the steering servo is back in the plane body, you can use a pushrod/sleeve setup and the end of the the sleeve is fixed at the nose gear end and thus sets a rigid height.
Or even if a nearby servo has enough distance to get that done in time.
On a very close servo, like yours, if you make the control horn hole a perfect fit to the pushrod, and make sure the pushrod Z bend is also an accurate 90deg in its mid section that goes in the control arm hole (or whatever angle the install needs for that Z-bend mid angle) then that will keep the pushrod at the required height to still enforce the leg to be straight on retraction. You can even use complex kinks/bends etc in the pushrod still.

F-22 pics:
Annoyingly you can't see the quite complex steering pushrod shape in the pics - the leg stays straight across its travel range. The pushod comes off the servo control horn and immeditely heads 45deg out sideways and then turns back to parallel just at the inner foam side wall - so it goes maybe 10mm outwards first. As soon as it goes parallel again, it goes 45deg 'downwards', relative to true up.down, then 45deg back to level - so again about a 10mm change in position.
This is all done to bring it into the steering slider rod at the exact required height alongside the retract so that it has that control over the leg steering STILL as it folds up. Basically it is 'steering control' - not via servo but via the pushrod controlling what HEIGHT the steering rod remains at. Because when retracted the height of the pushrod controls the rotation of the leg then. (any servo motions then are just making it slide along the steering rod)

Because I use 1.6mm pushrod wire, and drill a 1.6mm 'clean' hole' in the servo arm, and nylon is very strong really, it maintains that height position operation fine over the long term.
But even better is when you can BRACE the pushrod somewhere near the steering arm end... you can use a slotted bit of 'anything' that allows side to side freedom, but not height change. Even half way from servo the the clevis.
IF you can fit that in there - very often you can.

An issue with correcting steering ATHE END is that it can have flopped to an angle by any amount BEFORE getting to those, and already having hit the fuselage sides whilst retracting - so you really want a way that control steering to be straight ALL the way.

Extra Note:
And one more thing to aim for.... is matching the 'required pushrod height' to being mid way (approx) down the steering rod. This just so happens to be an almost 'must be' resultant of this setup anyway - but you want this so that there is enough steering rod for the slider to slide from end to end along it, before the servo steering (if you used that when retracted) drives it to one end and binds then. AND that the steering rod LENGTH is truly long enough too allow that.
Many supplied 'ready to go' retract steering arms are just a bit short, though many are JUST long enough. If not long enough... make your own to replace that.
If this is not done correctly you will get 'servo buzzing' on retraction.

A lot of WORDS needed to explain it all, but once you know this stuff it is easy and second nature to aim for in your pushrod steering setup!! A properly done pushrod steering ROCKS!! 100% solid and accurate steering and wheel retraction.... just like a real plane! LOL (pull-pull wire... super sucks!!)

...
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Last edited by PeterVRC; Jan 27, 2013 at 09:03 PM.
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Old Jan 27, 2013, 09:11 PM
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PS: The F-22 does not have the added 'slotted guidance bit', because with the three 45deg steps in it, there is not enough length in the 'final straight' to the steering rod slider to fit one!
The pushrod moves something like 20mm but only has 15mm of straight left - due to the distance used by the clevis attaching etc.
The servo arm is at the rear end of the servo - but I could have hacked rearwards into the fuselage bottom another 20mm (easily), to move the servo more rearwards.
If the steering rigidity ever flounders over time I will do that then. Or V2 of the F-22 if I ever got another one, LOL.

I will start my second Meteor in a week or two (the schedule so far anyway)....
It will be 6S and I am starting to even dislike 5S !
4S... HATE big time.... useless rubbish for good EDF's (cost and battery abuse etc). Currents are just too high when decent power.
5S... quite good really, verges on adequate for the majority of cases.
6S.... ahhh, "current demand ease" for outputs equal to 5S, and even a bit more. Though it will take a bit more time to pass to get a better assessment of the pro's and cons of it all.
4S is hands down out the window. But 5S is still 'very good'. Yet to decide on any 6S problems.
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Old Jan 27, 2013, 09:43 PM
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Where do you find the metal steering arm??
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Old Jan 28, 2013, 12:57 AM
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fg1972's Avatar
Australia, Melbourne
Joined Jul 2010
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Thanks Peter,
I think I understand what your'e saying and if I do understand correctly, in my picture #2 is it better for the pushrod to be parallel to the steering rod? If this is the case I can do another pushrod with the z bend in the right place to achieve this or I can fit a linkage stopper on the servo horn that will place the pushrod further away from the horn.

I've tried really hard to keep the steering rod slider to sit in the middle of the steering rod to get ample servo travel both ways when in the retracted position but as you can see in pic#2 the slider sits more to the left. If I make the steering rod any longer it will touch the retract base in open position, if I unwind the pushrod clevis to make it longer then the servo needs to be further away from the retract but back to square one in relation to the slider being more to the left instead of centre.

One thing I've found really annoying (giving me the sh!ts really) is that you cant slowly move the retract trinion by hand to see what its trying to do. Instead you have to operate the retract with power which is full open or full close which is way to fast to get a grip on whats going on. Maybe I can dig up an old retract to use as a dummy and remove the threaded shaft so the trinion can be moved be hand.

@TheCure,
The steering arm was in my parts box, not sure where it came from originally but pretty sure it came with a set of struts that are now long gone.
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Old Jan 28, 2013, 05:24 AM
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fg1972's Avatar
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MK II
Changed Z bend to linkage stopper to get servo push rod parallel to the steering rod in the retracted position. After setting it like this, the strut doesn't twist when closing (thanks Peter). I'm leaving the locating pins just in case.
Also lengthened the slider rod a few mm to just clear the strut base when extracted which provide a bit more servo travel when retracted.
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Old Jan 28, 2013, 08:13 AM
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Yes, that linkgage stopper would be good to allow rotation at the arm, but no height change in the pushrod.
I mentioned in the prior post.. it just geometrically works out that if your slider (of your type used - small) is in the correct spot for the folding aspect to work, then it ends up roughtly mid way of the slider rod, IF the rod is long enough. Well usually all works out close to right.
I guess part of that is how much pushrod travel you are using to steer - the greater thatis the more change the steering rod length will run out when steering if the leg is retracted.
Maybe yours has a lot of pushrod travel? Too much steering ability?

I also use an extra channel to mix from the rudder for the nose steering, and I enable/disable that from the gear swicth position too. Thus it cannot steer once the retract switch is used anyway. Fine IF you have a spare channel to 'waste' on that. (I pretty well use 8ch RX in all aircraft bar some sub 1000mm ones)
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Old Jan 29, 2013, 03:52 PM
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fg1972's Avatar
Australia, Melbourne
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Ok, I'm happy with the front retract configuration.
Setting up nose wheel retracts (0 min 22 sec)
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Old Jan 29, 2013, 03:55 PM
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Have dremmelled away some foam in the nose of the fuse to slide the assembly in place from the battery tray.
Originally I was going to glue a thin piece of plywood into the fuse, then slide my retract assembly into position & secure it via screws so it can be removed if unnecessary but it is a bit awkward to do so I might just epoxy the base of the assembly into position and if I need to get something out, can cut away a section of foam from the bottom of the fuse and just glue it back.
I'll have another look tonight, might change my mind or come up with another idea.
Also have done some very light glassing inside the nose area and wheel well where I have removed a fair bit of foam.
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Last edited by fg1972; Jan 29, 2013 at 04:00 PM. Reason: extra info
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Old Jan 29, 2013, 04:42 PM
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That has all worked out very good there!
It would be a handy thing to have a complete removable unit, in situations where that can be viably done. Probably more often easier in larger aircraft.
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Old Feb 09, 2013, 04:43 PM
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HK Meteor - Grass Field

Hi,

I'm looking at buying the HK Meteor, but where we fly is a grass oval or a gravel carpark in country Australia. I've got a HK f-86 that I can't launch for this reason - can the Meteor handle grass takeoffs or am I wasting my time?

Thks Dingo
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Old Feb 10, 2013, 03:41 AM
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fg1972's Avatar
Australia, Melbourne
Joined Jul 2010
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The stock wheels are a descent size so Gravel might be ok.
If grass is short and surface is reasonably smooth it may also work.
Either way, if wheels don't work too well, this plane flys extremely well without wheels.
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Old Feb 10, 2013, 08:04 PM
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I used to take-off from a football oval. The stock legs are just 'spring wire' and that is actually best for grass anyway. They still bend, but are easy to bend back straight as required.
So it is likely you too will be fine from grass in its stock form.
I would not want to be taking off an EDF from any dirt or gravel strip!! That would be asking for a fan disaster sooner or later!
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Old Feb 11, 2013, 05:37 AM
RC Airplane (Recently Crashed)
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Quote:
Originally Posted by fg1972 View Post
The stock wheels are a descent size so Gravel might be ok.
If grass is short and surface is reasonably smooth it may also work.
Either way, if wheels don't work too well, this plane flys extremely well without wheels.
How do you launch it without wheels? - I tried and have a bent nose for my efforts
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Old Feb 11, 2013, 07:39 AM
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hehe, there are videos of people hand-launching them... not too far back in this thread.
Generally a very steep upwards angle launch. Which would seem too steep for its power in many cases, but they all work.....
Holding mine, I donlt like the feel of it for a hand-launch! It feels like it would struggle, but maybe it just does it easy anyway. (900w 5S CS10 system).
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