Rhino track failier?

[team222badbrad]

If that's the case I think it would be better to change the screw so it has a smaller diameter and can be tightened without a socket such as a hex head, but I doubt you can source that in self threading style.

I just seems that's the area that needs to be modified to make the most strength in addition to the ribs.

Any thoughts on a material change such as Nylon?

[Breadbocks]

It seems like the fact that there's an edge rather than a chamfer/fillet where the well for the screwhead begins (radially out from the center) might be a point of failure. All of the fractures pictured are at the depth of the well, so I think having an edge there to bend around is contributing somewhat. Just a guess though.

[Kevin Sevcik]

Originally Posted by team222badbrad

If that's the case I think it would be better to change the screw so it has a smaller diameter and can be tightened without a socket such as a hex head, but I doubt you can source that in self threading style.

I just seems that's the area that needs to be modified to make the most strength in addition to the ribs.

Any thoughts on a material change such as Nylon?

Fastener Superstore apparently has them in flat head or pan head with (shudder) phillips drive. Assuming these are "Taptite" screws.

[Andy Baker]

Originally Posted by team222badbrad

Any thoughts on a material change such as Nylon?

We are thinking of this, but the shrinkage of nylon as it comes out of the mold is far different than polycarbonate. The whole mold would have to be remade if we were to go with nylon.

Andy B.

[team222badbrad]

Just to inspire some thoughts:

In the radio control truck/car world all manufactures use "standard" plastics.

Often these plastic parts such as suspension arms, bearing blocks, etc. will break easily and often.

It is known by many to upgrade these parts made by an aftermarket company called RPM. http://www.rpmrcproducts.com/

This company guarantees their products from breakage and are made of a Nylon material.

I've never broken one of their parts, but many OEM parts made from "standard" plastics.

I'm not saying you should change the plastic, but I'm just offering some experience I have with RC's.

They survive the impacts because of the flexible nature of the Nylon.

With that said I do not know how positively or negatively that may have an impact.

I also like the idea of inserting a bushing into the pulley until a more permanent fix is determined.

We will probably source something tonight as a bushing would at least allow the pulley to remain fully supported on the axle if a failure were to occur at the bearing.

[KrazyCarl92]

Originally Posted by Andy Baker

We are thinking of this, but the shrinkage of nylon as it comes out of the mold is far different than polycarbonate. The whole mold would have to be remade if we were to go with nylon.

Andy B.

This may not necessarily be the case. Nylon 6-6 (AKA Polyamide) can shrink at a wide range of rates depending on what filler is used with the resin. The desire to avoid fillers for fear of reducing impact strength was mentioned, but some fillers can actually improve impact strength.

So it may be possible to mold Nylon 6-6 parts with your existing mold and get close to the same shrink rate. However, the problem may be over-constrained due to the compounded effect of fillers on both shrink rate and impact strength (i.e. there may not exist a filler+resin for which the impact strength is improved, while maintaining your current geometry).