Cog belt break tensioner

Andrew Burr, VP, LLc lead designer submitted the following introduction:

The following is an old photo from my racing past. This photo shows one of my early cog belt drives and engines that I built. I have other pictures that I will post when I have the time. This picture shows that building cog belt drive systems is nothing new to me, in fact I have been building them since 1992. The engine is also a one-off billet engine that I machined from solid billet aluminum. If you have followed motorcyle drag racing you will recognize my "Overkill Drag Engine" pictured below.

I think it is important to point out that I have been designing and building race engines since the 90's and that I have worked under such famous people as Ross of Ross Racing Engines who was one of my early mentors. Ross also helped me with technical advice during my racing years. I have a shoe box full of old photos from my raceing days. Not too many people learn to weld at the age of 10 as I did and the best part is I have the pictures to prove it.

Since I have had a passion for flying all of my life and have enjoyed a carreer as a commercial flight instructor and Jet pilot, it is natural for me to channel my love of engine design into the Rotorway helicopter power plant. What I have done is bring every component of this old design engine up to 2009 racing technology. By incorporating titanium parts as well as other state-of-the-art technology into the new Vertical Performance Systems, LLC engine we have cut weight, inertia losses, and internal friction which allows more horsepower transfered to the drive system.

We have also designed two versions of this new engine, one normally aspirated and the other turbocharged and intercooled. We are also nearly ready to produce our own engine cases, water jackets, and heads. It is our plan at Vertical Performance Systems, LLC to shortly produce our engine as a stand-alone package for the experimental aircraft industry. Our engines are able to be run both horizontally and vertically.

We have also begun preliminary design work on the Vertical Performance Systems, LLC main rotor transmission and tail rotor transmission which will replace the belts in the Rotorway helicopter. You can just imagine what is comming next. Stay tuned to this web site as we pour our hearts, talents, and finances into products designed to enhance your helicopter flying experience.

Andrew E Burr XIV
Vertical Performance, LLC
Po Box 213
Cassville MO 65625

VP Elastomeric Cog Belt tensioner System

Please note that VP is currently testing this application of this very tried and proven elastomeric tensioner. Only many hours of flight time will prove that this application is better than the engine oil/hydraulic tensioner supplied by the factory or the untensioned Pro-Drive cog belt system.

To date we know of 2 cog belt breaks that have occurred with the AP design cog belt system. Orv Neisingh was flying with Larry Stuckman when the cog belt on Larry's ship snapped as they were on their take-off run.

They were traveling forward at around 12 mph, and at around 6 feet skid hight with the nose of the helicopter lowered and accellerating when the belt snapped. Due to the normal amount of right anti-torque pedal needed to keep the ship's nose aligned with the direction of travel, when the cog belt broke, the engine torque was disconnected from the drive train so the nose of the helicopter immediately swung to the right and the ship dropped to the ground.

The helicopter hit the front left skid sideways and started to experience a dynamic rollover to the left. Somehow the pilot was able to keep the ship upright as it swung around and as it slid to a stop sliding backwards the tail rotor blades dug into the grass surface.

The helicopter had extended reinforced skids and actually did a pivot on the front left skid and landed backwards but the ship remained upright. Both Larry and Orv credit our extended and reinforced skids with aiding in the helicopter remaining upright. We are happy to chock up one more Rotorway helicopter save by our extended reinforced skid design. If you have not already added our skids to your helicopters safety features, now is the time to email us and order your set.

Below is a photo of Larry's ship as it landed facing back in the direction from which it came. The skids are deformed but the did exactly what they were designed to do, support the weight of the helicopter during an emergency landing.

In the photo above you can see that Larry had installed the extra support bracket and it adequately supported the stabilizer from breaking free duing the landing.

The photo below shows what Larry and Orv saw when he removed the covers

The following two photos show the front and back of Larry's cog belt following the break

Orv and Larry asked us to design a mount for an elastomeric tensioner that is commonly used for tensioning cog belts to replace the engine oil hydraulic tensioner that came with Larry's cog belt drive. See the photo below of the same setup that Larry had before it broke.

We consulted with a cog belt manufacturer that we have used for many years and whose belt has a higher HP rating than that used with the AP/factory system. VP constructed a new mounting system and shipped it to Orv for flight testing. Orv and Larry are presently testing this system. It has a larger diameter tensioner wheel that is also longer than standard to meet the engineering criteria for the cog belt that we are using. The belt is one that we have used on our drag race bikes for many hundreds of hours with excellent results and reliability.

Orv and Larry plan on putting many hours on this setup and after this first week of testing the results look very promising. This tensioner has been used on this belt in many other applications with great success so we have very high expectations as well.

We have shot a video of both the AP engine oil pressure tension system and the VP constant elastomeric tension system during the engine start up sequence. Links to both are found below.

On the AP system the start pulses of the engine allow for great variations in the tension of the cog belt during engine start because the Rotorway engine starts eratically due to not having a heavy fly wheel. It is our opinion that the lack of engine oil pressure causes a lack in tensioning of the cog belt, both on the tension side and on the slack side, during the engine start sequence. It is also our opinion that it is this lack of tension on the cog belt during the critical engine starting process that caused the cog belt to run slack and ride up onto the drive cogs of the drive wheel. It is our opinion that this scenario caused the hyper-extention of the support fibers in the cog belt which led to their failure.

The cause of the belt break experienced on Larry's ship, according to the belt manufacturer engineers, was exactly that, at some point the belt was run too loose under load. The belt was adjusted to the proper tension but the oil pressure tensioner does not apply tension to the belt until the engine is running.

The videos in the links below show both tensioner systems, with the cog belts adjusted to to settings reccomended by the factory, during the engine start. These videos were both taken at the Sho-Me Helicopters, LLc training facility on the same day within 5 minutes of eachother. We state this to confirm that both cog belt drive systems were at the same exact temperatures during the first start of the day for both systems.

You can make your own conclusions from what you see happening with the cog belts on the videos.

Following initial flight testing by Orv and Larry, VP is installing this cog belt tensioner on Frankenstein for flight testing with the new Vertical Performance Systems, LLC turbocharged/intercooled engine to gain operational hours along with the new engine system.

VPhelo has now installed our elastomeric tensioner and stronger cog belt on the Pro-Drive system and are flight testing this installation in the field. There have been several of these untensioned cog belt systems that have broken cog belts in flight causing substantial damage to the helicopters. With the prodrive system the secondary needs to be re-shimmed as the temperature changes to keep the belt tight. This is difficult to do and thus is usually ignored until a belt breaks from running too loose, usually in the colder weather.

The VP elastomeric tensioner system is now available for installation on the Pro-Drive cog belt system. Contact Andrew for more information and to order your VP Elastomeric tensioner today.