Which way is the mold tapered?

[Kinser Racing]

Is the inside or the outside of the wheelbore larger due to the mold taper?

 

[GravityX]

For what it's worth, here is a cross sectional cut of a 2009 BSA wheel. The image does not depict any sort taper that I can see, but this is only one sample. But I guess if we are only looking for a .001" taper I may not see it anyhow.

 

[~JBD RACING~]

I have noticed a lot of inner hub tapering .. But I don't think if affects speed or performance

 

[bracketracer]

Mr Kinser, on the stock BSA wheels I have seen, the outer hub has a smaller bore than the inner hub. Not by much, maybe .0005-.0007" smaller.

 

[Guest]

For what it's worth, here is a cross sectional cut of a 2009 BSA wheel. The image does not depict any sort taper that I can see, but this is only one sample. But I guess if we are only looking for a .001" taper I may not see it anyhow.

It has to have taper or it would not release from the mold.

 

[GravityX]

BSB that makes all the sense in the world. You just never know what you're going to learn here. In your opinion BSB, do you believe the .0005" - .0007" taper, as suggested, is a reasonable value to allow proper release of the mold? Now you have me as curious as Kinser about this, I certainly don't know.

 

[bracketracer]

On a semi-related note, does anyone know who makes the wheels here in the states for the Scouts?

 

[Guest]

BSB that makes all the sense in the world. You just never know what you're going to learn here. In your opinion BSB, do you believe the .0005" - .0007" taper, as suggested, is a reasonable value to allow proper release of the mold? Now you have me as curious as Kinser about this, I certainly don't know.

http://www.plastics1.com/Articles/articles.php?Department=cim&article=62 I think .0005 to .001 would be a reasonable amount of draft in the length of the bore to have the wheel release. If you look at the inside of the wheel you will see three round marks. These are marks from the ejector pins which aid in getting the wheel out of the mold.

 

[GravityX]

If I have done my math correctly and assuming the draft angle is at a minimum of .5 degrees, as suggested in the article, and the length of the bore is approximately .300" in length, the calculated taper would be around .0026" or my math is wrong. /images/boards/smilies/crazy.gif

 

[bracketracer]

BSB that makes all the sense in the world. You just never know what you're going to learn here. In your opinion BSB, do you believe the .0005" - .0007" taper, as suggested, is a reasonable value to allow proper release of the mold? Now you have me as curious as Kinser about this, I certainly don't know.

http://www.plastics1.com/Articles/articles.php?Department=cim&article=62 I think .0005 to .001 would be a reasonable amount of draft in the length of the bore to have the wheel release. If you look at the inside of the wheel you will see three round marks. These are marks from the ejector pins which aid in getting the wheel out of the mold.

I'll be darned. I would have guessed those marks were from the gates! Learn something new every day!

 

[Guest]

Hey GX,

I checked your math and you are right on.

However, My pin gages say that this is not right.

I have noticed the same numbers as Bracket posted on my pin gages.

Perhaps due to shrinkage of the material after cooling?

 

[5KidsRacing]

If you look at the inside of the wheel you will see three round marks. These are marks from the ejector pins which aid in getting the wheel out of the mold.

I think those are the 3 spots where the wheel was injection molded, not where the ejectors hit....

 

[Guest]

If you look at the inside of the wheel you will see three round marks. These are marks from the ejector pins which aid in getting the wheel out of the mold.

I think those are the 3 spots where the wheel was injection molded, not where the ejectors hit....

You might be right. I would have to see how the spru set up is on the mold.

 

[GravityX]

If you look at the inside of the wheel you will see three round marks. These are marks from the ejector pins which aid in getting the wheel out of the mold.

I think those are the 3 spots where the wheel was injection molded, not where the ejectors hit....

Agreed...

 

[Guest]

If you look at the inside of the wheel you will see three round marks. These are marks from the ejector pins which aid in getting the wheel out of the mold.

I think those are the 3 spots where the wheel was injection molded, not where the ejectors hit....

This was the way I thought it worked too. I heard that the old wheels were injected from the tread (which left sprue marks on the tread) . These are the marks that most scout rules are talking about when they say that the tread can be lightly sanded to eliminate imperfections.