Custom Billet Shift Knob for Toyota Tacoma (2-1/4" diameter). ***Utilizes factory boot.***

I'm probably getting ahead of myself, but for those following along this is probably important decision making material.

The only issues I see for this 2.0 design would be Delrin in cold environments. Thermal expansion coefficients for delrin are going to greatly differ from that of any metal it is mounted to. Given that most buying delrin are in warmer environments, it is not an issue for any that have been sold to date.

My worry is that even though DuPont claims toughness of delrin down to -40C, that it might become brittle enough to split under the force of the interference fit that is created due to shrinkage (lol?) in the cold. I suppose this means we should also keep them out of the pool in the summer, ammirite?

I make the ring attachment at .0005-.001 slip fit (and then of course three 1/8"x .4375 dowel pins @ 120 degrees apart).

The collar over the knob I made to about .005 slip fit for myself, and if I know it is going to a colder environment I can increase the ID of the collar to compensate. This is only if delrin is desired, as I can always make it out of any material in stock. There is nothing to worry about with all metals.

All of the speculation in the world isn't going to help, just need to test this at some point when I figure out how I can do that.

 

Everyone is an early adopter at some point, even myself!

I will probably never stop fiddling with these designs, it is too fun.

 

Wow, this is awesome!
Now I want a Ti 2.0 version.

 

So there is a chance the delrin ring could crack in cold weather?

 

edit: math fix

Extreme cold, sure ... but you shouldn't have anything to worry about. The math doesn't look bad, and you probably don't see anything much under 0F. Inside of a truck there is no worry of wind chill.

Coefficient of Linear Thermal Expansion
Delrin: 6.8 x 10^-5 (.000068 per degree F)
6061 Al: 13 × 10^-6 (.000013 per degree F)

The parts were machined at 70F, so

at 0F you are looking at .0047 change in delrin, and .001 for Al. .0037 difference. Double that for a diameter and you're at about .0067 interference fit when subtracting the nominal slip fit gap. I've seen success with up to 1/16"/1.5mm press fit into delrin (well, acetal in general) bushings, so it is plenty strong enough to handle a 1/10 fraction of that. The main concern is when you are approaching the operating temperature failure point (-40 F/C). It should perform within specs to that point. Looking to you Canada and Minnesota.

I am also ignoring a lot of variables, like the metal knob base should help regulate temperature changes, and probably countless other things. I just do not see a point in giving it more thought than it requires.

Somebody please feel free to check my math on this, I might have fudged a conversion or something. The numbers make sense based on my anecdotal experience, so I'll leave it at this.

 

That looks killer. Nice work!

 

This is some seriously impressive work! My truck is getting built in a week, and I really think I'm going to need one of your shift knobs... All the best on the new gig, and let us know when you're back to selling these.

 

Thanks! I will do my best to get back to this asap.

For now, I'll put a perfectly good knob in danger again to "knurl" it. I just couldn't quit this feature.

 

Worth it.

 

If ya squint, it could be escher-esque. Actual, Escher was all about math in his art. The knurl is the product of an algo, so...


Very nice Rick!

 

Escher? Nice. And I haven't even reached my final form.

 

http://www.mcescher.com

 

http://www.mcescher.com/gallery/mathematical/

 

I know who he is, my gf was an art history major. I dunno, it's a stretch but I'll take it.

 

It's so beautiful...

 

Dropped back in now that my internet is up and running. Still love my knob and it still looks great. How much does one of those little lathes cost, anyway?

 

Welcome back dood...hows the new digs!

 

There is so....much...work to do. The people who lived here before me were here for 30 years and made some questionable decisions. Like venting the bathroom directly into a tiny attic, or installing the hot water heater still on its shipping pallet. But they did leave me a 5hp, 80 gal air compressor in the "garage". I'll have to post some pictures of the first floor/garage. I can park like, 4 tacos in there and still have room.

 

Those are some pretty sweet shift knobs. May have to get one when I'm focusing on the interior customization!

 

I’m interested in one once your up and running again