Bowden cable replacement -> servo

[mjcp]

Hi all,

Any bright ideas for replacing a bowden with a servo?

More specifically, options for getting the servo wire to where the servo will be:

options I can think of:

Try to run the new cable down the bowden sheath?

Try to extract the sheath and draw the servo cable as its removed.

"drill" a new cable run and draw the servo cable through to the new servo location.

The wing is foam / wood veneer / glassed / wooden spars

I have plenty of servo cable and the tools to properly terminate, so I can split into 3 and make to length etc.

Thanks,
Marc

[Philkiteflyer]

Try to run the new cable down the bowden sheath?

Thanks,
Marc

In keeping with my moto (K.I.S.S) that would be my choice. Solder the servo wire to the Bowden (if you can) or use the bowden to pull a string that can then pull the servo cable. Don't want to mess up a wing with more holes . . . just creates weakness.

Good Luck,
Phillip C
New Zealand.

[Peter Balcombe]

Try to run the new cable down the bowden sheath?

Thanks,
Marc

In keeping with my moto (K.I.S.S) that would be my choice. Solder the servo wire to the Bowden (if you can) or use the bowden to pull a string that can then pull the servo cable. Don't want to mess up a wing with more holes . . . just creates weakness.

Good Luck,
Phillip C
New Zealand.

I would also vote for that approach in order to use the existing foam penetration path. As long as all 3 conductors go through then fine, but I suspect the bowden tube hole may be a little small to get decent size cable through - even if done as 3 separate cores to optimise fit.
As Phillip says, slide a single piece of wire through tube to act as a pull cord for servo wires, soldering wires to pull cord to get a good attachment in a minimum diameter. Lubricating the wires with a a smear of soapy water may also help them slide through rather than do it dry.
Bowden tubes are often stuck pretty well to the foam cores, so getting it out may be difficult, particularly if long/ curved

[roo Hawkins]

The problem is that servo wire might be to thick to slide inside bowden cable. The way I do my servo channels is by heating and long metal rod of round 3 or 4 mm with a blow torch and push it in to the foam from the root to the servo box .

[roo Hawkins]

The problem is that servo wire might be to thick to slide inside bowden cable. The way I do my servo channels is by heating and long metal rod of round 3 or 4 mm with a blow torch and push it in to the foam from the root to the servo box .

[mjcp]

Thanks all, I concur with the preferred idea of using the bowden tube as a conduit for the servo cables; the existing cable is freely moving, so the route is snag free and low radius etc.

I'll see how three servo strands fit and go from there!

Marc

[FrankS]

I did this on my old Pat Teakle HP18, I used a larger diameter tube and then "drilled" around the existing bowden cable. After first cutting out the servo boxes so I didn't have to drill round the curve.

HP18 flew like this for several years, and the final crash wasn't a result of these mods