Crazy AMT for Aerobatics – fliploops - MadSagitta / Madslide / Kulbutin - RC Groups
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Feb 25, 2008, 12:43 PM
Phil.Taylor's Avatar

Crazy AMT for Aerobatics – fliploops - MadSagitta / Madslide / Kulbutin

EDIT 17 March 08 - finally managed to do the fliploop/somersault thingies
see post 93

EDIT 11 March 08 - this thread is becoming a repository of "wisdom" about BPLR style "madflight" - especially the crazy fliploop/somersaults There's even a wonderful contribution from BPLR himself (post No.61). It started with a mad thought and an experiment though...

EDIT - now with video - see post No.41

Warning – this thread contains crazy stuff (but no furry coverings or milquetoast ) No slopers were harmed (well, not much) in the making of this mini-build experiment.

Many of us will have seen this king-sized Madslide video,
and wondered how on earth to execute the “flip loops”/somersaults – especially the consecutive ones…
The obvious answer is to get crazy movement on the All-Moving-Tail (AMT), as detailed here (the other video of formation slope aerobatics is pretty cool too):

What’s not clear is whether such crazy AMT movement will work on other designs – yes there’s been the Kulbutin (some like it, some don’t), but why has the idea not been emulated by others (anyone for a MadFish or MadWasabi?)

So – I have an unfinished kit for a Voltij – And I’m wondering… MadVoltij !!!
Will it work? – How to get the crazy AMT movement? – is it worth the effort to mod. it?
So - I though about it some more – and decided that an EXPERIMENT was needed before hacking about a perfectly good kit.
1x Sagitta – well used – which in standard form has a standard elevator, and also has 2x separate elevator linkages – and which I’d like to be able to return to its standard state afterwards...
1x AMT from another slope project – in cool looking chrome blue vs. flouro yellow
1x optimistic hour?, effort, headscratching & general cursing…
(beer would have been helpful, but none in the house )

“Mini-build” Photos below…
1. Well, the tail is approximately the same size – looking hopeful
2. And the rear tubes on the AMT are the same size as the rear joiner wires
3. Look! - crazy AMT movement !!!
4. But the links are a bit problematic
5. OK – here we go – fit the control horns to the AMT
6. Oh dear – screws too short – desperate search begins – trawls up Futaba servo mounting screws – perfect
7. Out with the soldering iron – off with the old links – some creative bending & soldering
8. Look! – joined up crazy AMT!!! – but only on one side – and the UP is not too crazy.

Well, its obviously going to need some more thinking, and more TIME – so here is where I quit (whilst still ahead - just) - off to bed – zzzzzzzzzzzzzz
Next part to follow...

(whos going for crazy movement)
Last edited by Phil.Taylor; Mar 17, 2008 at 07:43 PM.
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Feb 25, 2008, 12:50 PM
Phil.Taylor's Avatar
Round 2

9. Needs a bigger servol horn for more travel – haven’t got one in JR fit – mmm – Futaba servo? – looking good
10. But no-one ever told me that Futaba servos go the opposite direction to JR
11. And this is where I discover that the rudder trim on the Tx is going submarine – something coming loose – it’ll just have to wait.
12. Kinky links needed in order to clear the AMT to get lots of UP movement… (gotta love kinky stuff – its what goes flexy & wobbly & fluttery – but this is an experiement – no DS speeds here) and YES, success, crazy UP AMT movement
13. Now for the other side… major pause, considerably time, effort & more than a little cursing here, but eventually its all lined up, and…
14. SUCCESS !!! OK, so its not as much movement as I’d hoped for, but its still a crazy 55 degrees each way – hopefully enough for a flight test experiment ?
15. Oh, nearly forgot the re-programming – that’s 50% travel & 30% expo on low rates, and 100% travel & a huge 70% expo on high rates – looks/feels about right around the centre point i.e. flyable

Now, just need:
a. wind in a suitable direction
b. “slope time” – off from other mundane matters…
c. someone with a video camera to record the event (could be difficult – haven’t got one)

So – don’t expect a flight test “result” from this for a few days yet, and in the meantime, a few questions for you all:
i. Will the MadSagitta be able to fly fliploops/somersaults?
ii. Would you attempt this on one of your slopers?
iii. Suggestions please as to how to do this on a VoltiJ, in the neatest possible way, whilst still keeping the tails removable for storage & transport.

and of course the usual slope forum comments, general heckling & stuff…

(who’s got crazy movements...)
Feb 25, 2008, 01:23 PM
If it can-it will!
cliffhanger's Avatar
This we've gotta see!!

How about getting some more rudder movement ala Madslide?

I'm sure you've got the family digi camera with video facility- strap it to you're forehead with some duct tape

C'mon Phil brighten up our gloomy winter days

Feb 25, 2008, 01:53 PM
Phil.Taylor's Avatar
Can't get more rudder cos of the way its hinged - if this experiment works the MadVoltij will get more.
digicam (with short video facility) has gone into hiding - no-one knows where
H.Q. digicam doesn't do video, nor does my phonecam.
Got Tx back off - trimmer mount broken
epoxy now splooged around in there - fixed.
Last edited by Phil.Taylor; Feb 25, 2008 at 02:42 PM.
Feb 25, 2008, 03:09 PM
AKA Cactus
Phillybaby's Avatar
on the madslide i don't see huge horns and stuff, just a fixed part of the surface so the rods don't hit it as it moves and what looks like normalish servo throw with the horn right over the pivot point.
Feb 25, 2008, 03:21 PM
Phil.Taylor's Avatar
Originally Posted by Phillybaby
on the madslide i don't see huge horns and stuff, just a fixed part of the surface so the rods don't hit it as it moves and what looks like normalish servo throw with the horn right over the pivot point.
Yep, that's what I'm seeing too - my experiment doesn't use fixed surfaces (or cut-outs) cos I want to re-use (all of) the tail too - hence the kinky control runs & slight gap between the tail & fus. The catch is - how to do the "Madslide thing" & make it so the tail is removable. Is it worth doing? - don't know until I "chuck it & flip it"
Feb 25, 2008, 03:50 PM
AKA Cactus
Phillybaby's Avatar
why is a madslide tail not removeable? it only appears to be a single carbon joiner so must be fixed, but a little joiner at the back, bit of friction and your sorted
could go right upmarket and have magnets on the joiner ends and two buried in the tail halfs at the end of the joiner tubes.
Feb 25, 2008, 03:59 PM
Phil.Taylor's Avatar
but how to get a positive "drive" from one side to the other? - or use 2 sets of pull/pull cables - one set each side - messy!
Feb 25, 2008, 04:05 PM
AKA Cactus
Phillybaby's Avatar
rear pin? means cutting a fair bit of tail, but less so the closer to the pivot
Feb 25, 2008, 09:12 PM
Piscine Promulgator
surfimp's Avatar
Phil, right there with you on this subject my friend. I think it's well worth experimenting with, and that your plan of attack (using the Sagitta as guinea pig) is a good call.

One idea to maybe consider is the below, originally from Francois Cahour's website (currently not loading for me, but normally here: ). Basically it's a normal internal bellcrank driven by a pull-pull cable, using a turnaround pulley just tailward of the bellcrank. Won't work for every design, but it should work for many. I've included Francois's PDF as well, for extended discussion (in French).

Beyond that, to get maximum movement you need longer arms on your servo output shaft than you have on your bellcrank / elevator stab. Mechanical advantage and all that Given suitable ratios, you should easily get the rotation you need.

I would investigate using a square joiner rod for your stab, so you can dispense with the secondary pin.

Even though it's so "me too" to say it, I have been giving exactly the above quite a bit of thought the past few weeks. I plan to test some theories on my next builds, including my "Nemo" Voltij. Good times!

Feb 25, 2008, 09:53 PM
Fun ain't cheap!
droydx's Avatar
I'm liking that set up....tres mechanical!

Square joiner? Diabolical!

Latest blog entry: Douglas Silhoutte wing cores
Feb 25, 2008, 10:47 PM
Piscine Promulgator
surfimp's Avatar
Originally Posted by droydx
I'm liking that set up....tres mechanical!

Square joiner? Diabolical!

I think you really only need the turnaround pulley if you want your stab mounted higher up the fin such that you can't get a straight shot back to a double-horned bellcrank mounted right on the fin axis.

The square joiner rod thing isn't mine, it's been done on a number of planes including the Kulbutin if I'm not mistaken. But it's a "simple solution to complex problems" so of course I'm a fan

Another idea I've had towards the goal of maximum stab rotation is a cam-shaped bellcrank. The theory is that, with the "fat" side towards the pull-pull cable, you get fine resolution, but when you whack to full throw you get to the "skinny" side of the cam and the stab goes to "mad" rotation.

I'm sure it's been done before, but I haven't seen it.

Feb 26, 2008, 02:17 AM
Twisted and Confused
flyonline's Avatar
Why not go the whole hog and add TWF as well? That way you could fly with the fuse at wierd angles as well... heck, it may even slow down a little.

Feb 26, 2008, 03:40 AM
Phil.Taylor's Avatar
Hi Steve - thanks for the input. Interestingly, the pull/pull/turnaround thingy is what was originally supposed to be installed in the fus of the "project" glider the AMT was on - using a standard AMT horn. Its a Wildflecken from the early 1970s so the idea has been around for a while - I didn't build it that way though, I just used a snake / outer bonded to bottom of the fus - works just fine. (the actual build was 2004 - I got the kit part built - had been stored by previous owner/builder for 30 years or so!) The "project" bit was hacking the gf fus so it would fit 3 different wings - 120 inch thermal (the original) - 100 inch 4xservo - and 67 inch fully symmetrical.

The cam thingy looks an interesting idea - one full turn & you get mad movement - but isn't that pretty much the same as just using a small horn & rates on the radio?

Square joiner & some engineering - most promising - need to find suitable bits though. I see you're already on the "fishy" thread with one of these in it.

MadVoltij - I've wondered about just using the standard tail arrangement, but elongating (considerably) the rear slot, so it becomes a semicircle. Nasty structurally, but with reinforcement internally should be OK - what do you think? Not sure you need the full movement anyway - 50-60 degrees is probably enough for the crazy fliploops. But I wont know for sure until I've flown the MadSagitta.

Edit - mmm TWF? - that's a MadTWVoltij then - TW plus flaps - could be done - but just might never get started...
Feb 26, 2008, 03:56 AM
Long to be flyin'
Antonsoarer's Avatar
Phil, some more creative (or possibly destructive! ) ideas for your melting-pot (that would be your brain ), I didn't see these anywhere above:

1. Independently driven AMT's for opposite or complimentary aileron effect like the Russian fighters and F18s use. Not sure what the effect would be!

2. Canard AM planes

3. Canard AM fin


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