Paramotor Safety

Safety Cage Add-On w/Video

Aug 26, 2009 Jeff Baumgartner Safety Ring Modification | Cage Intelligence | A Better Paramotor

You can now buy a safety ring, suitable for many brands, from Skycruiser Manufacturing for $65. Thanks to Leon Wacker for working with me on this and making it available. Shipping adds approximately $15. It comes in 3 segments with connectors and Valco snap buttons. This is just one of several pieces of prevention. You are always the most important one.

Besides the kit you'll need four 4 1/2" hose clamps with a 1/2" to 5/8" range to connect the hoop to your radial arms (spokes). If you build it yourself, the parts list is supplied below.

Leon's version has a flat area at the bottom which looks good but that is not necessary if you make your own. It is there because a tube bender needs a flat area to start and finish bending. What is important is that the radius be about 1" less than your prop for maximum protection. In other words, the hoop should be 1" inside the prop.

This video shows how to mount the hoop (watch it on YouTube here).

Building It Yourself?

Here is what you would need.

1. Twelve feet of 1/2 inch .058 wall aluminum tubing. Here is one source.

2. One foot of connector tubing, 3/8 inch, .058" wall aluminum, available from McMaster-Carr #89965K348

3. Package of snap buttons for telescoping tubing, available from McMaster-Carr #94282A250.

4. Four hose clamps, 5/8" diameter.

Skybolt Version

Skybolt designer Jeff Baumgartner also developed a retrofit for the same purpose for the Skybolt. Either one works. We do recommend that whatever solution you adopt goes all the way around to the bottom. There have been at least two hands chopped from the bottom of the cage--both by highly experienced pilots who didn't think it was possible. These increase strength where its needed most—just forward of the prop tips and in front of the radial arms and will work on many different brands. His design, based on the "Better Paramotor" safety ring, was improved after witnessing a pilot suffer a prop strike injury. As the video below shows, he has succeeded.

In the accident that spawned this, the pilot's quick action prevented a catastrophe that still cost him several days in the hospital and a large scar on his arm. Thankfully, he will have full movement of his arm and hand when it all heals up.

The retrofit puts a hoop around the most vulnerable section of cage, where the netting would otherwise be easily pushed into the prop.

The idea of this design is that by putting on a solid hoop forward of the prop tips, you provide both rigid strength there, at the closest spot to the prop tips, but also keep the netting farther away. Quite a few prop injury accidents would have been prevented by this design.

It is still critical for the pilot to exercise intelligent starting technique—insuring that the throttle is at idle before attempting to start and bracing yourself in a way to handle unexpected thrust.

it's always safest to start the motor on your back so, if you don't have electric start, and there's a willing someone around, use them.

These accidents happen in a lightening quick flash of inattention. Treat the motor with enormous care when starting.

I've also created a 3D model of the "Better Paramotor" design that's intended to show more accurately how some changes could be made to existing (and future) designs that keep the paramotor's general character while dramatically improving safety. A screenshot is shown at right but it will be done as a quick video with narration highlighting each of the suggestions. There are many other ideas listed on Better Paramotor web page but these will be the most important. The model will be included in parts of the Master Powered Paragliding series.

Note: This was done for testing only,
never use the cage to hold your paramotor for starting or runup.

 


This is one easy way the ring can be fixed to your motor. Only two of these are needed on each side since the radial arms (spokes) provide support.

 

 

 


1 & 2. Computer model of a paramotor with safety ring and other features that could dramatically improve prop safety.

2. The PPGPlans.com Skybolt with safety cage designed by Jeff Baumgartner.

Aerodynamics of the Ring

I asked Dana Hague for an assessment of the Safety Ring's drag, assuming that airflow would be much faster at full power due to the prop. He did not disappoint. Here it is:

The drag coefficient of a cylinder at the Reynolds numbers we're talking (~20K) is around 1.0. Temperature variation between 59°F and 0°F are small enough to make no difference in the coefficient of drag (Cd), and only minor effects on air density (approx 0.5% between 60 and 100F).

So: Drag is ½pV²CdA where p=.002378 (air density) V is velocity in ft/s, Cd is drag coefficient, A is frontal area (unlike a wing where you use projected wing area). So, your 1/2 dia x 141 tube has an area of 0.49ft², and 40mph is 59 ft/s, thus the drag is 2.03 lbs. At 60 mph, it would be 4.6 lbs. Etc.
 


© 2016 Jeff Goin & Tim Kaiser   Remember: If there's air there, it should be flown in!