Do it yourself paraglider line measuring device

Note: This measurement device is not a proper replacement for having your wings regularly checked by an experienced inspector. There is more than just line lengths that effects your safety in the air. But having your own measurement device is fun and helps understanding the dynamics of paraglider line lenghts. And it is a great excuse for having a 3D-printer ;-)

The basic idea was to create a device that assists in measuring paraglider lines. The materials are all simple aluminium strips and profiles, cheap bearings, 3D-printed parts and screws. The equipment used are a saw, a machine drill (on stand), thread cutting tools (M3, M5), some files and a 3D-printer using PLA filiament. The 3D-printed parts replace the smaller, more complicated parts which are harder to make in metal.

There are two main parts, the riser attachment ruler with 5kg weight and laser target and the measurement ruler with the laser distance meter. The latter part is optional, but it greatly simplifies measuring.

This is the second version of the measurement ruler part, which replaces the aluminium later meter cage with a 3D-printed part. The attachment to the ruler-trolley is simplified, making the laser-meter a separate part.

Riser attachment ruler

The riser attachment ruler consists of two aluminium U-profiles. The inner one is just wide enough for two risers to be attached side by side. The lines emerge from the other side. The inner profile glides inside the outer on eight bearings, four vertical and two at either side. A wide pulley on the outer profile provides frictionless movement of the line to the counter weight. Four 3D-printed parts connect the bearings to the inner profile.

Outer profile dimensions:
Width 80 mm

Height 50 mm

Wall thickness 5 mm

Length 800 mm

Inner profile dimensions:
Width 60 mm

Height 30 mm

Wall thickness 3 mm

Wength 600 mm

Bearing dimensions (8 in total):
Outer diameter 16 mm

Inner diameter 5 mm

Length 5 mm

Brand 625ZZ Bearing 5x16x5 Shielded Miniature Ball Bearings VXB Brand

Measurement ruler

The measurement ruler is an U-profile with two L-shaped guards attached, so the laser meter trolley movement is restricted to one dimension; forwards and backwards. The 3D-printed carrage has bearings pointing in all dimensions perpendicular to this measurement axis.

The L-profiles are screwed with five Phillips flat head M3 screws, approx. 25 cm apart.

The center plate is connected by four M3 screws to the 3d-printed laser meter carriage and the basis for the Laser meter cage (this is an old version of the cage).

The line attachment point and handle are attached directly to the base plate. The prototype has a laser meter cage for the Leica GeoSystems D110 device. This device is Bluetooth enabled and can insert measurement data into a spreadsheet (on Windows 10, with a special driver installed. Alas not yet with Linux).

Measurement profile dimensions:
Width 50 mm

Height 30 mm

Wall thickness 3 mm

Length 1000 mm

Measurement ruler L-profile dimensions:
Width/height 10 mm

Wall thickness 2mm

Length 1000 mm

Measurement ruler center plate:
Width 30 mm

Length 120 mm

Thickness 4 mm

Bearing dimensions (12 in total):
Outer diameter 10 mm

Inner diameter 3 mm

Length 4 mm

Brand 623ZZ 10 Bearing Shielded 3x10x4 Miniature Ball Bearings VXB Brand

3D-printed parts

The zip contains both the STL and the original SCAD files. The files are created with OpenSCAD and slized with the Prusa version of Slic3r. Printing is done with a Prusa i3 MK2 printer.

highTwoWheels5.scad - attached to the inner riser attachment ruler. Two bearings are attached; one horizontally to the side and one vertically to the bottom. The latter uses the separate axis1.scad part.

axis1.scad - a 5 mm cylinder to be pressed in the highTwoWheels5.scad part.

laserTrolley3.scad - The laser trolley connects to the bearings on one side, and the base plate on the other side. All bearings are attached with M3 cylinder screws. Threading is cut onto the holes. The red bits are some of the bearings, not to be printed.

laserCage.scad - The cage for the Leica D110. It is separately of the handle/line-hookup-point attached to the base plate, so can be replaced by another laser meter device (with custom cage).

backWheelPlate2.scad - attached to the end of the outer riser attachment ruler profile to provide overhang for the counter weight pulley.

measureRailStopPlate1.scad - cosmetic plate to close of both ends of the measurement ruler. Prevents the trolley from escaping.

pulleyFiller2.scad - fills the space between the 16 mm bearings and the 18 mm (inner diameter) tube and keep the bearings in place.

targetPlate1.scad - the laser target plate

targetHolderPinch2.scad - the part connecting the inner riser profile and the target plate. It is padded with thin black rubber (actual bicycle inner tire, glued with super glue).

Remarks

the M3 screws used for the laser trolley upper and lower bearings (horizontal axis) should have a low-profile head, or a filed down head. There is room for about 2 mm.
the measurement ruler L-profile attachement to the U-profile is done at five points over the length of the 1000 mm. M3 screws with flat (sunken) heads are used. The length is 5 mm maximal, to prevent interference with the laser trolley horizontal axis screws.
the laser target part should have a very solid attachment to the inner riser profile. The current holder is not sturdy enough.
The riser attachment ruler uses 16/5/5 bearings and the measurement ruler uses 10/3/4 bearings. If I would redesign the riser atttachment ruler, I would use the smaller bearings. The 3D-printed axis aren't as sturdy as expected and the result would be more compact. But then again, attaching two full-size risers could use some more space...
more photo's and info on request. There are no drawings, the designs are "grown". Note: I do not produce or sell these devices. The item described is a prototype and made just for personal interest and it might entertain or inspire other people. All information is open source. But I am interested if you build your own version.
The Leica D110 is slightly tapered, and the laser bean is not quite parallel to the bottom surface. I fixed this by small strip of aluminium in the clip attachment hole. The dimensions are 20.5 x 19 x 2 mm. It is the 19 mm which makes the correction.

Inspiring video's and information online

Paragliding Laser line measurement Designed and build by Alan Ford
Rail-Check by Highadventure This might be the Rolls-Royce of paraglider line measurement devices
Andre Bandarra's video on the subject
Certika's video on line measurement (in french)
Useful information on how to measure your lines from BGD and what ranges are ok.
Christoph Faessler's low-tech solution (in german).
Manual for the device from Flugsport Service (in german).
Very luxurious device from Tomatosport in Slovenia
paraglidingforum.com For the latest news and pointers to interesting information.

fjkraan@electrickery.nl, 2018-11-03

	highTwoWheels5.scad - attached to the inner riser attachment ruler. Two bearings are attached; one horizontally to the side and one vertically to the bottom. The latter uses the separate axis1.scad part.
	axis1.scad - a 5 mm cylinder to be pressed in the highTwoWheels5.scad part.
	laserTrolley3.scad - The laser trolley connects to the bearings on one side, and the base plate on the other side. All bearings are attached with M3 cylinder screws. Threading is cut onto the holes. The red bits are some of the bearings, not to be printed.
	laserCage.scad - The cage for the Leica D110. It is separately of the handle/line-hookup-point attached to the base plate, so can be replaced by another laser meter device (with custom cage).
	backWheelPlate2.scad - attached to the end of the outer riser attachment ruler profile to provide overhang for the counter weight pulley.
	measureRailStopPlate1.scad - cosmetic plate to close of both ends of the measurement ruler. Prevents the trolley from escaping.
	pulleyFiller2.scad - fills the space between the 16 mm bearings and the 18 mm (inner diameter) tube and keep the bearings in place.
	targetPlate1.scad - the laser target plate
	targetHolderPinch2.scad - the part connecting the inner riser profile and the target plate. It is padded with thin black rubber (actual bicycle inner tire, glued with super glue).