Quote:
Originally Posted by JohnFogarty
In my research of the 118 press-bearing system they still had some method of tensioning the chain if needed. I'm not a huge mechanical guy. My background is mainly in electrical and programming, but I've started learning this stuff to help my team design better. How would one make sure the chain is tensioned properly without the use of tensioner blocks...I would assume some pretty accurate calculations have to be made.
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Talking to 118 at IRI about their 2013 drive, they had no chain tensioners, they relied on the walls of the tube to keep from throwing chain once it stretched out. IIRC they used custom 17T sprockets like the 221 robotics systems ones, they are essentially two sprockets on one hub.
Because you are only running one chain, you could use regular 17T sprockets inside the tube and they should fit fine (This would also make it so your wheels arent cantilevered so far, which is important because with only 4 wheels, each wheel is taking a lot of weight). A chain run that long though may not be as forgiving in terms of stretching, but unless you are in a district model I don't think you will play enough matches for it to matter.
As for bearing blocks, you are probably fine without them, but if you can get something COTS like the VexPro ones I definitely would. Even if the spacing between bearings isnt an issue, what you also have to look at is the support on the outside race of the bearing. Sheet metal teams (like 971) often times beef up areas around bearings with something as simple as an extra bit of sheet riveted on just so there is a thicker face for the bearing to sit on. This may not be critical, but with only 4 wheels taking the whole weight, I would play it safe.