Frank, Thank you for the details about the horn design. That is exactly what I was looking for. I really do appreciate your help despite it seeming like it is falling on deaf ears I truly am taking your wisdom into account. Also, thank you for the suggestion about the plastic to use. Now that I think what you said it makes sense. I finally got some new resin and parts for my Form1 3d printer. All the parts I have show were printed on my Makerbot which is cheaper and faster to use, but less accurate. I currently have some parts printing on the Form1 which I will use as the master for the silicone mold. Then I can test out the over-molding process, and get parts that are in the correct durometer rubber. I also plan on using the Form1 to make masters for the horns and cast them out of polyurethane. These should be single part molds and easy to make. Fingers crossed.
* - This brings up another question I had; I am going to mold them in a Shore A 70 rubber, which is basically the same as car tires. That was my best guess at what would be a good material for things. * *Why Roller Chain?* I will again restate the reasons for my design decisions. The idea of using roller chain as the foundation of my design gives me a few key aspects which I am fond of. It is a standard design with many off the shelf parts working with it. Most notably the sprockets. Using standard roller chain means that I do not have to make custom sprockets. This might seem like a small thing if you only planned on using one sprocket size. But I really like the idea of using any size sprocket. These sprockets are also already design with many different methods of attaching to shafts. McMaster has about 100 sprockets for #40 roller chains. Diameters range from 1.67" all the way to 15.57". Idlers with built in bearings, machinable bores, finished bore with keyway, nylon, metal, bushing, taper lock and more. In addition to the sprockets, you have tensions, idlers, and the design tools that help you select the perfect spacing of multiple sprockets in a chain system. I am still thinking robotics an not just tanks. If I were to design a system that has a molded connecting link this would be an additional part to design and I would have to make custom sprockets too. Like I said before I could design one sprocket, or maybe 10. But then I have the cost of making them, storing all the sizes, tooling costs, and I am never going to have 100 types for each size chain. In addition to the sprocket and accessory aspect, roller chain is very durable and has known tensile ratings. This is similar to the metal bands that are placed in the solid rubber tracks found on construction vehicles. The rubber tracks I am getting injection molded are not taking the loads. The chain will take it. I like that aspect as well. One final thought about the roller chain links is the cost. Roller chain is $13.92 for 10 foot of #40 chain. #40 chain has a pitch of 0.5", so that means 240 links. That is 5.8 cents per link. I don't think I could get links made that cheap even in quantities of 60,000. Maybe I am wrong. Or maybe I am missing something obvious to you guys that know more about this. But those are the design aspects which made me like this idea of using roller chain. You mention the width of the track not being flexible in this design. I agree with that. I have not found a good way of doing that. It is much cheaper to injection mold over a dowel pin then to make a hole. Talking with the injection molding companies I work with, having a hole will make the mold tooling and per part cost go up substantially. I even asked about molding over a metal tube. But that is problematic as well. I think for now I will have to settle for picking a single width for each size chain I want to work with. For now that is #35 chain being 3" width, and #40 chain being 4" width. - Do you think you could use an idler sprocket that meshed with the drive chain as bogie wheels? You might not need horns with that design. I have never seen that on tanks. maybe I am missing something obvious? As always thanks for the comments guys. I have got a lot of great suggestions, information and mostly just some place to talk about tank track. My couple friends are not really very interested in talking about bogie wheels, tread design. They just nod and say yeah that sounds cool. -- -- You are currently subscribed to the "R/C Tank Combat" group. To post a message, send email to rctankcombat@googlegroups.com To unsubscribe, send email to rctankcombat+unsubscr...@googlegroups.com Visit the group at http://groups.google.com/group/rctankcombat --- You received this message because you are subscribed to the Google Groups "R/C Tank Combat" group. To unsubscribe from this group and stop receiving emails from it, send an email to rctankcombat+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
