Doug, Thanks for the advise about the injection molding. I agree that a long through hole is a pain but possible if you design around it. That is one of the reasons I liked the overmolding design. You do not have to worry that problem. It also makes a much cheaper mold. I am hoping to use of the shelf pins with grooves for snap rings. But one that fits is a little tricky. That is one of the draw backs of using the roller chain is I need pins that match the rollers. If I designed my own connecting link it would open up the ability to design around a pin. But that would mean custom links, and custom sprockets to drive it. I would prefer to avoid that. If the trade off is designing and fabricating the pins, or the link / sprocket I would pick the pin. They are very simple parts. Also, the quanties that I am thinking about are around 15,000 treads. So that would be 30,000 pins. In that quantities I can't imagine not being able to get the pins as cheap as any of the shelf product I could find.
I know that this sounds quite high quantities. I could do less, but the price per part goes up then. 15,000 treads is only 625 feet of track. Or about 300 kits of 2 foot tracks. Anyway, hopefully my works 3d printer is not busy the next few days. I want to print some test parts and do a pilot run of molded parts in rubber. Plastic tracks just don't feel quite right. Josh On Tuesday, February 10, 2015 at 3:43:13 PM UTC-5, RocketMan wrote: > > One thing I learned about injection molding is that you can't mold a part > with a long hole through it. Even a 1" long hole would need a substantial > cone shape to it to provide enough draft to release the part form the mold. > It makes sense when you think about how the mold works and the parts are > produced. You can use a 'sliding shutoff' technique, but that would produce > a part with a lot less strength right where a track link needs it - along > the joining pin. > > - Doug > > > ------------------------------ > *From: *[email protected] <javascript:> > *To: *"rctankcombat" <[email protected] <javascript:>> > *Sent: *Tuesday, February 10, 2015 3:34:15 PM > *Subject: *Re: [TANKS] New Track Idea > > One thing I learned about injection molding is that you can't mold a > part with a long hole through it. Even a 1" long hole would need a > substantial cone shape to it to provide enough draft to release the part > form the mold. It makes sense when you think about how the mold works and > the parts are produced. You can use a 'sliding shutoff' technique, but that > would produce a part with a lot less strength right where a track link > needs it - along the joining pin. > > - Doug > > ------------------------------ > *From: *"Frank Pittelli" <[email protected] <javascript:>> > *To: *"rctankcombat" <[email protected] <javascript:>> > *Sent: *Tuesday, February 10, 2015 1:59:41 PM > *Subject: *Re: [TANKS] New Track Idea > > All the more reason to make everything from molded plastic as much as > possible and, more importantly, to use a design where a small number of > parts (say 4) can be used to build a variety of different track widths > and configurations. With a slight modification of Garnet's T011 design, > such a goal is achievable. If you develop the following parts: > > - 1 inch long pad > - 1.5 inch long pad > - simple link > - horned link > > they can be combined to build virtually any tank track configuration > used during the last 100 years and could also be used to develop tracks > for a wide array of robots. Design a plastic sprocket to mate up with > the links and it's a complete system. Best of all, assembly and repair > would only require inserting and removing straight pins that either > press it into the links or that have slip rings on the ends. In either > case, such pins are stock items. > > And, from a business standpoint, you maximize revenue by producing all > the parts yourself. Modular, all-in-one solutions are the goal of all > product companies because that's what the market always wants. > > > On 2/10/2015 11:18 AM, Joshua Updyke wrote: > > I am looking at being able to make these in small batches myself, but > > mostly at trying to make them in bulk and sell to hobbyists. > > -- > -- > You are currently subscribed to the "R/C Tank Combat" group. > To post a message, send email to [email protected] <javascript:> > To unsubscribe, send email to [email protected] > <javascript:> > 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 [email protected] <javascript:>. > For more options, visit https://groups.google.com/d/optout. > > > -- -- You are currently subscribed to the "R/C Tank Combat" group. To post a message, send email to [email protected] To unsubscribe, send email to [email protected] 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 [email protected]. For more options, visit https://groups.google.com/d/optout.
