pic: Floating Zip Tie Chain Tensioner

[R.C.]

Originally Posted by rocketperson44

I meant for different chain sizes. #25, #35.

They work for either one, just like mcmasters.

[JesseK]

This is a fantastic and simple idea! Now let's hope they don't ban zip ties... We would want #25 chains, but probably only 1.25" in length because we have some short chain runs to deal with from the transmissions.

Have you done any efficiency experiments, e.g. how much efficiency is lost due to these tensioners when compared other methods? Examples include autotensioning (sliding a wheel out like 254/968/etc), simple rotary tensioners that use delrin or similar plastics, or the old adjustable bolt/sprocket method.

If you find that there's more loss (due to increased contact surfact area) you could experiment with teflon or oil-impregnated plastic surfaces. Also, you could change the geometry in the channel itself to be curved convex rather than simply flat. This is how the secondary tensioners on Harley Davidson motorcycles work -- turn a bolt and a convex-curved piece of teflon raises against the chain to fine-tune the tension.

< edit >
Another thing you could do is create a working relationship with a company such as AndyMark or a local plastics mold company, who can mass-produce these for teams and give your team a % of the revenue. The upside to this is that it should be low-stress supplemental revenue for your team. The downside to this is that you miss producing and selling these yourselves, which opens up a whole new can of worms in opportunities for more people from your community to learn and participate in your program.

Food for thought.
< /edit >

[Cory]

Originally Posted by JesseK

Have you done any efficiency experiments, e.g. how much efficiency is lost due to these tensioners when compared other methods? Examples include autotensioning (sliding a wheel out like 254/968/etc), simple rotary tensioners that use delrin or similar plastics, or the old adjustable bolt/sprocket method.

I can't speak for specifically how much loss there is between different types, but the method of sliding the wheel is going to be by far the most efficient, as it's the only style of tensioning that does not touch the chain and add more friction to the system.

[Tom Line]

Originally Posted by rc_cola1323

Also another question, would teams buy this if they were available???

There's an easy answer to that.

It depends on your price point.

Unfortunately, with something this small and this easy to make, your labor (or mill time) is going to KILL you on pricing. Now, if you could get a plastics shop to start cranking them out by the thousands off a small injection mold so that you could sell them for a couple of bucks for a pair... well... I'll tell you one team that would be interested!

Get in touch with AndyMark. I'm sure they go through this all the time and can help you out. Incredible idea!

[dtengineering]

An interesting design, and an interesting discussion on IP. (Intellectual Property... patents, copyright, etc.) The CD community does a pretty good job of giving solid information on the challenges and benefits of patents, and dispels some common myths such as the protection offered to engineering designs through copyright.

It looks like these could be mass produced fairly easily on a table saw with some fairly simple jigs. There are also some alternatives to UHMW that are worth considering. A local firm (North Vancouver, BC) produces a graphite/epoxy composite for lubricating the side of train wheels. This is an extremely hard-wearing, low-friction compound that can easily be shaped with wood-working tools, but has the added benefit of lubricating the chain (or wheels) as it slowly wears away. They gave us some and we used this to tension our chains three years ago, with a grooved sliding tensioner that was adjusted cam-style on just one side of the chain. It worked great. But I've lost their contact information, sorry.

As far as the profitability of marketing this design, the tensioners would end up being a fairly low cost item (the raw materials are commonly available and the machining steps relatively simple) so it would require a significant volume of sales to generate a large amount of revenue, and, as mentioned several times, a large amount of revenue is required to justify the cost of a patent.

However it is possible to file for a provisional patent at a much reduced cost ($500 is the ballpark figure that runs through my head), and while that only protects your design for a year, that may be enough time to test market it and/or license the design to someone who is willing to pay the costs of obtaining a full patent.

Whether or not this is a patentable or profitable design, it is a good one and one to be proud of. It may well be worth the effort of doing a patent search (google patents and freepatentsonline.com help the individual inventor get a start) as well as a search of the web for similar designs. (Remember that what matters is that you were first to invent, not first to patent. Even if you were to get a patent, if someone were to demonstrate that the device had been invented 50 years ago they could have your patent overturned... regardless of whether the original inventor had filed for a patent or not. There is a whole section of patent law on the issue of "first to file" vs. "first to invent", but your main concern here is to look for "prior art"... ie. has anyone done this before?) It may also be worth going through the exercise of setting up a small-scale production run, developing a brand name for your product, and marketing your product just as an educational exercise. If it turns a profit... great!

Jason

P.S. Also remember that a patent doesn't prevent someone from using your idea... it merely gives you the right to sue them for damages if they do... and a US patent only protects ideas in the USA. If a US patent is expensive, then protecting your idea world-wide is phenomonally expensive (any idea what it costs to get a patent translated in to Japanese?) That doesn't mean don't "go for it" if you want the experience... in many ways the educational value of developing your design is likely to be far, far greater than the commercial value... just as the educational value of building a FIRST robot is far, far greater than any commercial applications the robots might have.

P.P.S. Should you decide to patent in Canada, I can introduce you to some excellent Canadian patent agents who know a thing or two about FIRST.

[Cory]

Originally Posted by dtengineering

(Remember that what matters is that you were first to invent, not first to patent. Even if you were to get a patent, if someone were to demonstrate that the device had been invented 50 years ago they could have your patent overturned... regardless of whether the original inventor had filed for a patent or not.

I hate to be a downer, but this isn't the first time a chain tensioning device like this has been seen in FIRST. I know for a fact that I have seen it on at least 2-3 robots some time ago (like 5-8 years ago). Can't recall who.

[dtengineering]

Originally Posted by Cory

I hate to be a downer, but this isn't the first time a chain tensioning device like this has been seen in FIRST. I know for a fact that I have seen it on at least 2-3 robots some time ago (like 5-8 years ago). Can't recall who.

I wouldn't regard your comment as being a "downer". It takes nothing away from the designer, who came up with the idea independently and creatively, to say that other bright and talented people have come up with similar designs. In many ways it is a compliment to the effectiveness of the design.

From a patenting point of view it is also extremely helpful to know exactly what the "prior art" is so that you can describe precisely how a design differs from the prior art and what benefits your design offers. Perhaps this design is simpler to produce, is more reliable, uses less expensive materials, or is easier to adjust. If you don't know about prior art, and sufficiently differentiate your product from what has come before, you may spent a whole lot of time and money getting a patent only to discover that you can't enforce it due to the prior art... so knowing that there are similar designs out there in the public domain is useful for the inventor.

It is extremely difficult to come up with a revolutionary mechanical design. After centuries of designing developments tend to be evolutionary rather than completely new. Often those incremental improvements are quite profitable and quite worth patenting, even though they may only improve performance in some small way. I can see how this design offers some incremental improvements over what I've seen before... and the suggestion to use a hose clamp is possibly another incremental improvement.

Given that the discussion of patents, in the absence of a business plan, is purely academic, knowing that there have been similar desgins in no way marginalizes the "great idea" factor for the designer. So rather than viewing your comments as a downer, I'd view them as evidence that this design is on the right track!

Jason

[R.C.]

Originally Posted by dtengineering

I wouldn't regard your comment as being a "downer". It takes nothing away from the designer, who came up with the idea independently and creatively, to say that other bright and talented people have come up with similar designs. In many ways it is a compliment to the effectiveness of the design.

From a patenting point of view it is also extremely helpful to know exactly what the "prior art" is so that you can describe precisely how a design differs from the prior art and what benefits your design offers. Perhaps this design is simpler to produce, is more reliable, uses less expensive materials, or is easier to adjust. If you don't know about prior art, and sufficiently differentiate your product from what has come before, you may spent a whole lot of time and money getting a patent only to discover that you can't enforce it due to the prior art... so knowing that there are similar designs out there in the public domain is useful for the inventor.

It is extremely difficult to come up with a revolutionary mechanical design. After centuries of designing developments tend to be evolutionary rather than completely new. Often those incremental improvements are quite profitable and quite worth patenting, even though they may only improve performance in some small way. I can see how this design offers some incremental improvements over what I've seen before... and the suggestion to use a hose clamp is possibly another incremental improvement.

Given that the discussion of patents, in the absence of a business plan, is purely academic, knowing that there have been similar desgins in no way marginalizes the "great idea" factor for the designer. So rather than viewing your comments as a downer, I'd view them as evidence that this design is on the right track!

Jason

I would just like to say thanks to everyone and I am currently talking to AndyMark right now. Hopefully I can get this thing in the market.

[DonRotolo]

Originally Posted by Tristan Lall

So by copyrighting a drawing, you prevent someone from redistributing facsimilies of the drawing, but are not protected against someone reading it and implementing the object depicted.

Or, for that matter, someone re-drawing the drawing and distributing that.

Originally Posted by rc_cola1323

What if I just sell it to Andy Mark??

I know you're in discussions, so I won't comment specifically on that.

One option is to simply give them the idea for free (or some minor consideration, like a 20% discount on your next order). But, that depends on whether they 'want' something like that, or think it will sell. They have some small risk in the cost of manufacturing and inventory, but the risk is small only because the cost is low.

Another alternative is to ask AndyMark to market the product, and you simply supply it. They have little upfront expenses, aside from a web page on their site. You have a small expense, making several samples and a small stock for them to hold on to for orders. And you can make a few dollars for the team, or for yourself.

Just beware that if a LOT of teams want these, you may need to buy materials and make hundreds or even thousands* of them in just a few days - during build season. Getting a whole team to help - who gets the money? - might ease this worry.

I'm not meaning to suggest that AndyMark will do this, I'm just using their name as an example.

*We can only hope!

Don

[dtengineering]

Originally Posted by Don Rotolo

Or, for that matter, someone re-drawing the drawing and distributing that.

So long as it was not an exact replica of the drawing, then there would be no copyright protection. For instance the drawing could be re-drawn to a different scale, show dimensions in different locations, be in first angle rather than third angle projection, have some parts with slightly different dimensions, be a SolidWorks file rather than an Inventor file.... I would even go so far as to say that if the original drawing was drawn exactly to an established standard, then someone could re-draw it to that established standard and have a perfect duplicate without infringing copyright because no creative content went into either drawing. (The creatvity being in the design, not the drawing.) They may even be able to copy the drawing outright, just as they would a table of data, or a bare (non-artistic) chart or graph.

Oh, heck... here's someone who's written it up better and more authoritatively than I http://www.lawmart.com/searches/difference.htm

That is the value of a patent... it truly protects the idea of the design, which is the fundamental part of the invention rather than just an expression of the idea.

Jason

P.S. Good luck with manufacturing and marketing your design. It looks like a design that is extremely well-suited to mass production and once you get your jigs worked out you should be able to churn them out by the hundreds fairly quickly.

[Cory]

Originally Posted by dtengineering

P.S. Good luck with manufacturing and marketing your design. It looks like a design that is extremely well-suited to mass production and once you get your jigs worked out you should be able to churn them out by the hundreds fairly quickly.

I think it'd be best for him to step back and view this from an economical perspective.

Think about how many of these you need to make, how quickly each one needs to be made, and how much you need to sell them for to break even.

Then think about how many you think you can possibly sell.

If you do the math, I don't think it's a viable investment to try to mass produce these, or even make them on a fairly large scale.

To actually make money you need to be injection molding, not milling these. Injection molding is orders of magnitude more expensive than even the most generous estimate of demand for these.

Given demand, and cost of contracting these out to a machine shop, or time involved in making them yourself, I don't think you can come out on top. Especially given that anyone with a manual mill or even drill press with x+y table can make one of these in about 15 minutes.

Keep in mind that if you choose to make them or have someone else machine them, you have to be able to meet the criteria of a vendor, as well as be capable to potentially ship one to every team in FIRST, if they ordered one, within x time period (I think 5-7 days? can't recall).

[R.C.]

Originally Posted by Cory

I think it'd be best for him to step back and view this from an economical perspective.

Think about how many of these you need to make, how quickly each one needs to be made, and how much you need to sell them for to break even.

Then think about how many you think you can possibly sell.

If you do the math, I don't think it's a viable investment to try to mass produce these, or even make them on a fairly large scale.

To actually make money you need to be injection molding, not milling these. Injection molding is orders of magnitude more expensive than even the most generous estimate of demand for these.

Given demand, and cost of contracting these out to a machine shop, or time involved in making them yourself, I don't think you can come out on top. Especially given that anyone with a manual mill or even drill press with x+y table can make one of these in about 15 minutes.

Keep in mind that if you choose to make them or have someone else machine them, you have to be able to meet the criteria of a vendor, as well as be capable to potentially ship one to every team in FIRST, if they ordered one, within x time period (I think 5-7 days? can't recall).

That is why I am talking to Andy Mark, but Cory. Do you think these will sell if they are priced just right???

[M. Mellott]

Greg & Jason,

Thank you for setting me straight on the copyright issue, and for your thorough discussions.

I've mentioned this discussion to "those I mentioned in my post" who use this practice, but they swear it would hold up in court...oh well...

[JesseK]

Last night I took this into the preliminary CADs my team has for our '09 prototype bases, and we noticed an inherent flaw. Perhaps this is a flaw with all floating tensioners though.

If the two sprockets in the chain run are significantly different relative to their distance apart (e.g. 22-tooth to a 32-tooth, 6" apart) or their axes of rotation are not level with each other (e.g. transmission output shaft is higher than the wheel axle), this tensioner will have a tendendency to "drift" towards the smaller or lower sprocket and stay there without putting any tension on the chain. Is this correct or are we seeing something that isn't really true?

[Zflash]

Originally Posted by Cory

I hate to be a downer, but this isn't the first time a chain tensioning device like this has been seen in FIRST. I know for a fact that I have seen it on at least 2-3 robots some time ago (like 5-8 years ago). Can't recall who.

http://www.snapidle.com/chain_tensioners.htm We used these when I was working with team 507. they worked nicely however since then we have gone to other methods of chain tensioning and may or may not return to these in the future.