Bearing Tooth Gears

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Presented By:
Steve Knotts
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Tell us briefly about your project. Is it a work of art or does it serve another function?

The Bearing Tooth Gear is actually a functional technology that uses bearings in the construction of the gear teeth and of course bearings are being used for axle bearings to mount the gear housing. Currently there are 2 U.S. Utility Patents on the Bearing Tooth Gear (BTG) technology (5,371,704 & 5,704,248) and further Patents are undoubtedly available, if a market could be established for the BTG technology. The BTG technology use bearings inside the bearing teeth, or, the bearings are set in the gear housings. The bearing teeth are in rolling contact, instead of sliding contact, like conventional gear teeth designs. While it is obvious that rolling friction is much lower than sliding friction and therefore less energy is needed to rotate the gears; there are actually a number of other advantages to using rolling contact, instead of sliding contact. I will go into further detail regarding the advantages of the BTG technology in the following questions.

When did you start working on this project and how long did it take you to complete?

I worked for Boeing as a Design Engineer in the 1980’s and early 1990’s and during that time I saw an article in a Popular Science magazine that talked about a gear design that was known as Squirm-Drive gears. Their gear design was a type of worm-drive gear, where they had some roller bearings coming in contact with a large screw tread. As it turns out, conventional worm-drive gears have a very large frictional loss, maybe as high as 70%, in worm-drive gear designs. Because of these high frictional losses, in conventional designs, the screw cannot be turned by rotating the gear, instead, only the rotation of the screw itself, can move the gear assembly. Although, with the Squirm-Drive design the frictional losses were so low, the gear could actually turn the screw! Again, driving the screw with conventional worm-drive gears is impossible. So after seeing this Squirm-Drive design, I wonder why other gear types with rotating gear teeth, weren’t explored. I left the Boeing Company back in 1991 and I started a consumer products company that designed and manufactured unique fireplace equipment but in the early 1990’s I explored the patenting of the BTG technology. I fabricated a prototype 1 to 1 BTG design (see photo) and I got a video made up regarding the merits of the BTG technology. This video is not downloaded on YouTube yet because of its size (about 10 minutes long) but I can supply you with a CD/DVD of the BTG video, if this would be useful. Anyway it took about 2 years to get the first Patent approved, the prototype constructed and the prototype and video completed.

What was your goal in building this project?

My goals with the BTG technology was to see if I could get an existing gear manufacture, to take on the production of a wide range of bearing tooth gear designs. And of course, that company would need to pay me a royalty to manufacture that wide range BTG’s. So I contacted a number of existing gear manufactures and I actually got a number of parties expressing some level of interest. Unfortunately the companies that were seriously interested wanted further proof testing on the BTG technology, but I didn’t have the needed capital to build and test any full scale BTG designs.

Does your project help to solve a problem? If so what problem?

As to solving problems, the BTG technology can solve a wide range of problems, especially for large gear sets. One of the nice things about the BTG technology is, it can easily be serviced in the field. Back in the late 1980’s I found an ad in a Thompson Guide that talked about the cost of the downtime on some types of gears. At that time the ad mention the possible downtime costs being as high as $10,000/hr. Of course current day downtime costs would be much higher than the 1980’s cost estimates. So consider the current downtime costs of a gear set in an offshore drilling rig, or a large mining crane, or what happens if a gear fails inside the transmission of a U.S. Navy ship? I would assume those numbers could be in the hundreds of thousands of dollars per hour, not only $10,000/hr. Again, back to that gear ad; that company touched on how quickly they could service that 10.0 ft diameter gear but of course it still took a lot of time to service that gear. The gear had to be taken out of the transmission; then the gear had to be shipped back to the gear manufacture’s facilities; the gear manufacture would need to weld the old/new teeth back to the gear housing; then the gear would need to be machined and re-heat-treat; the repaired gear would need to be shipped back to the facility and finally they had to reinstall the reworked gear set. Of course large gears are normally quite unique, so they normally don’t have new 10.0 ft diameter gears ready to ship. Now consider a BTG; the BTG gear housing could be designed not to fail but instead the bearing teeth would fail first, since these parts could easily be shipped within a day. And if a facility, such as an oil drilling platform, wanted to play it safe, they could keep replacement BTG teeth on site, so the rework could be done in less than an hour.

What makes your idea unique?

The reason the BTG technology is unique from standard gear sets is not only the rolling contact but because of the numerous advantages that result due to this rolling contact. Again, if you examine large gear sets, you’ll note that the convention gear designs have relatively small gear teeth versus the size of the gear housing. You might ask, why are the gear teeth so small? If the gear teeth are too big with a conventional gear set, then there are several ways this gear set can fail. When the size of the gear teeth are too large, the sliding speeds between the mating teeth, will increase; when this happens there can be micro welding or scoring between the mating teeth. Also, pitting and general wear of the teeth will be more prevalent on large gear teeth, due to the higher sliding speeds and higher contact loads. So that’s why a 5.0 ft in diameter gear may only have 2.0” tall gear teeth. But the BTG types don’t suffer any of these failure types because the teeth are in rolling contact, not sliding contact. So much larger BTG teeth can be made. Also, because of the rolling contact, other type of materials can be used on the teeth, such as elastomers. With these larger teeth and the elastic materials, the gear sets can now take much larger impact loads without failure.

In what capacity are you using bearings and what type of bearings?

The BTG technology can use a wide range of bearing designs (e.g. ball, roller, etc.) to mount the bearing teeth. The bearing sets can be enclosed in the teeth or in the gear housing and seals could be added so that the bearings would not be exposed to harsh environments. And since the BTG teeth are in rolling contact they don’t need to be lubricated on the outside of the teeth. So again the teeth of a BTG can be exposed to dust, grit and moisture, while the bearings are being lubricated and sealed off from the environment.

What is the most important thing you want people to know about your project?

What would be nice for people to know is, the BTG technology can be used in a wide range of gear designs; from smaller gear sets, such a truck differential that’s not lubricated; to a large gear set for a ship or heavy machinery. To give you an idea of the need for such systems, I had a friend who was a Senior Chief on a U.S. Destroyer. My friend Hal and the Captain, were the only two that had a key to the transmission room. The reason they had such control was to prevent entry from a sailor that might have had a beef with the ship’s officers. If a steel wrench was thrown into the ship’s transmission, then whole ship would be down. And that ship would need to be towed back to the shipyards to be repaired. Kind of an achilles heel for war ships. As another example, consider a large crane where a major load shift on the cable could damage the gearing in the wench. Again the BTG teeth can be bigger and the teeth can employ elastomer structures, to where the BTG teeth would rarely fail but if they did, the BTG assembly could easily be serviced.

How will you use the $5,000 prize?

The $10,000 prize would be much appreciated but it will probably take some more capital to launch some of the BTG designs. Currently I set the BTG endeavor on the side but if Boca Bearings would like to get involved with the BTG, I am very open to focusing on the BTG technology again. But as to how I’d use the $10,000 prize, I’d probably employ it in another technology. The YouTube video I suggesting was for the SEM (Solid Ejection Material) shock technology. The SEM shock technology employs the high pressures that are needed to initiate the flow of polymers (e.g. plastics & elastomers). These flow pressures can range from 2,500 psi up to 35,000 psi! So relatively small structures (e.g. piston areas) can still deliver extremely high restraint loads. We’ve already run a number of high load drop test efforts and several full scale vehicle impact tests. If you would like to see some of our test videos and test reports, just type in SEMshocks into a Google search. So in summary, I’d like to make the point that both the Bearing Tooth Gear (BTG) and the Solid Ejection Material (SEM) shock technology have a great deal of payback potential but I haven’t gotten the needed investment capital to launch some of the initial startup markets. To give you an idea of one of those markets, consider the current bumper shock market. Some 70 million cars are produced each year and if we just got 5% of that market and 4 SEM shocks were used with each car and each of those shocks cost $15; then that one market would product $210 million per year in gross sales. Thank you for your time and consideration.

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