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ASK13 1/3 Scale

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Peter Balcombe
Posts: 1289
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: ASK13 1/3 Scale

Post by Peter Balcombe »

Hi Tjarko,
The drive pivot square tube/axle needs to be accurately located in order to allow the 2 arms to rotate smoothly as will cause extra friction or binding to occur at some point during rotation as is the case for any Schemp-Hirth brake setup.
I have used a peg & slot coupling between the servo disc & the square tube drive disc to achieve a degree of flexibility in the coupling, so the servo just needs to be notionally centred.
I just connected the discs before marking & drilling small starter holes for the servo screws, then screwing the servo into place.
Peter

Keith
Posts: 101
Joined: 07 Jan 2019, 18:18
Location: Lincolnshire

Re: ASK13 1/3 Scale

Post by Keith »

Hi Peter, the arms and drive assy.

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Cliff Evans
Posts: 425
Joined: 29 Dec 2019, 15:13
Location: Bristol
Contact:

Re: ASK13 1/3 Scale

Post by Cliff Evans »

3d printed drive arm for ASK-13 air brake
3d printed drive arm for ASK-13 air brake
3d Printed servo coupling for ASK-13 air brake
3d Printed servo coupling for ASK-13 air brake
https://lasercutsailplanes.co.uk
https://patteaklegliders.co.uk

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Peter Balcombe
Posts: 1289
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: ASK13 1/3 Scale

Post by Peter Balcombe »

Ok Keith, hopefully the following will do the job:

One pic below shows the blade parts (with internal ply spacer discs fitted, plus the 3D printed arms (with 5/32” bearing tube fitted at blade pivots & 5mm brass tube fitted at non-driven centre pivot - driven arm has a 1/8” square drive slot included in the printed part) for the as yet unbuilt RH brake assembly. 1st pic also shows the 3D printed drive disc + servo & std output arm fitted with 2 screw pegs for drive coupling to the 3D printed drive disc.

The other pics show back & front of the LH brake assembly installed in the test brake box, with & without the servo in position.

As per the standard plan arrangement, the blades are attached to the arms using 1/8” brass pins & then held in place with dabs of epoxy on the outside.
The non driven arm rotates on a fixed 4mm pin (could be secured on final installation with dabs of epoxy).

A short length of 1/8” brass tube is secured into the 3D printed disc at one end & pushed through driven arm via short 5mm O.D. brass bearing tubes epoxied into each side of the brake box wall. (The 1/8” Sq. brass tube runs nicely in the 5mm tube bearings).

If the square drive tube is fixed into the drive disc, then it cannot go anywhere as the servo stops it going one way & the brake box, the other.
The separate servo/drive discs arrangement allows any servo to be coupled to the square drive, rather than having to print correctly splined/fine detail drive discs for each servo option.

(The standard plan arrangement uses brass sheet arms with 3/16” & 5/32” brass tubes for main pivot & blade pivots respectively - everything being soldered together to ensure perfect alignment before separation into the bushed arms.
The pins are then 5/32” & 1/8” respectively for main & blade pivots)
1/8” square brass tube is slightly too big across the external diagonal to fit in a 3/16” (4.76mm) tube, hence the move to 5mm tube & 4mm pivot pin for this direct drive option.
Attachments
Forward side of box
Forward side of box
Rear side with servo
Rear side with servo
Rear side showing drive disc
Rear side showing drive disc
Set of CNC & 3D printed parts
Set of CNC & 3D printed parts

Keith
Posts: 101
Joined: 07 Jan 2019, 18:18
Location: Lincolnshire

Re: ASK13 1/3 Scale

Post by Keith »

Thanks Peter, i have the same setup on my Jaskolka a mate has made me some 3d arms and i have made new moulded blades, (ill post pictures soon) i like the drive system and will try and incorporate it in my Jaskolka. Nice build of a nice kit from Cliff.

Keith

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Peter Balcombe
Posts: 1289
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: ASK13 1/3 Scale

Post by Peter Balcombe »

Ok, getting ready to fit the brake blade assembly into the 1st wing .....
As there is very little room between the front 0.8mm brake box side & the main spar web, I decided to fit the 2 vertical main pivot support strips, drill through to the correct size for my installation (5mm & 4mm) & dry fit the 5mm driven end bearing tubes before fitting the brake box sides. Note that the support strips are not full width as they go between the 1/8” wing surface spars.
I couldn’t see how I was otherwise going to be able to accurately drill the holes through the support strips once in the wing!
I can now at least tweak the holes in situ if needed once hole alignment is checked, before fixing the tubes in place.

One pic below shows the rear box side with the support strips in place, drilled & tube in place, whilst the other shows the front side clamped in position in the wing.

Note that it is imperative that the 0.8mm sides sit cleanly onto the rib tabs, else the resultant gap to accept the blade assembly will be smaller than expected!
Attachments
6305DBE8-DD2A-4843-B656-A5C4CA5AC47E.jpeg
6FAC4198-503C-4480-B25D-3B9609C5DF88.jpeg

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Peter Balcombe
Posts: 1289
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: ASK13 1/3 Scale

Post by Peter Balcombe »

The first airbrake is now installed in the wing & operational :)

As expected, the resultant space between the two brake box faces produces a rather neat fit for the blade assemblies.
I ended up shaving a little off of the arm pivot bosses in order to get them to slide in (11.5mm).
However, the axles lined up nicely & the arms rotate well - at least until the blades start going into the box when there is a little bit of rubbing due to the blades being not exactly central/perfectly straight & the gap being only 2mm larger than the nominal blade width.
This area will need a little attention later, but is basically ok.
Note that I needed to re-position the servo with long axis parallel to the wing surface to keep the support plate edges under the wing surface.
Attachments
7B526C7B-E826-46C7-8BC8-479C04C30C1A.jpeg
4CDCD2A4-E82A-4E56-9E5D-BABD90D2DE60.jpeg
CEA76F25-F40B-4216-A637-844152BDB69E.jpeg

jack
Posts: 98
Joined: 20 Mar 2015, 21:55
Location: chepstow,south wales

Re: ASK13 1/3 Scale

Post by jack »

very nice work peter,l am about to take delivery of a k-13 kit from cliff....,will post a build blog as l go,the brake set up is a neat addition,....l have his petrel finished and ready for paint,just cant get it to him :evil: ,the k-13 looks to be a good deal bigger though ;) ;)

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Peter Balcombe
Posts: 1289
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: ASK13 1/3 Scale

Post by Peter Balcombe »

Hi Jack,
Yes you will need a bench that is 2.5m or so long for both the fuselage structure (without rudder) & each wing.

I’ve now put together the basic structure on each part except for the RH wing. Everything seems to fit nicely & the design seems well thought out.
You just need to be very careful to get the brake blades nice & straight in the vertical plane as I’ve found on the 2nd brake assembly build. If the 2 sets of blades do not come together nicely in line, the bottom of at least one blade will hit the outside edge of the box! ( I’ve just taken apart & re-assembled one assembly because the non-driven pivot arm was slightly off square ;)

The root end handful of ribs are only registered by notches in the false leading edge (rather than also by the main spar web), so you need to position these carefully to ensure the root rib is at right angles to the joiner tubes.

Happy building,
Peter

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Peter Balcombe
Posts: 1289
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: ASK13 1/3 Scale

Post by Peter Balcombe »

A little more done on the fuselage.
I had forgotten to add the rear fuselage internal. Cross bracing between formers F13 &. F18, so this has been done. Note that this goes as the waist stringer (S2) level. Together with the upper CNC ply plate & the upper fuselage skin, this forms a strong box structure to resist rear end flex.

Fuselage servos now fitted (rudder horn length to be extended) & tow release.
Meanwhile, the main joiner tube & rear incidence pin tubes have been installed.
Attachments
72232BA8-F8B0-4F9A-A6A5-4CBC8BC6BC82.jpeg
4A724727-8E65-4394-8274-1452E7E3348F.jpeg
6BDAA78D-B4A6-4A57-ACD3-1A88A2E3C2E9.jpeg
BDBE0CDA-61F4-429D-8A44-D20C7D70F8EF.jpeg

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