weighted shift knob?

[Austin David]

well, I was modeling my design on what I assume is an original, based on the knob I saw on a '68.  Eventually I was thinking of using wood, but I am presently distracted with prototyping to settle on weight and design.  I'm 3D printing the prototypes, figured I'd do wood myself the hard way, or outsource it locally.

 

That said -- on a whim I ran a rubber knob.  Sort of long story but the outcome is hilarious and amazing.  I used rubber mostly because that was in the printer already, and I broke the plastic test part while moving the threaded sleeve.  I took it for a spin tonight and it's AWESOME.  The plastic one (tested yesterday) feels pretty good, but sounds like a maraca under 45 or with partial throttle (I hadn't potted it, the lead was still loose).  I had a good feel for the weighted deadblow, and was moving the sleeve back to an empty model, and I broke the ball.  No big deal, but rather than swapping out the material I figured I'd just print off this rubber unit.  The rubber material itself is flat black, and is what I am using for the gapfiller / sleeve between the shift boot and the ball.  It holds the locknut to keep the ball from rotating.  It's about 95A which is sort of hard, about like a tire sidewall.  Feels good under skin, but it's not shiny and not really polishable, so I wasn't planning to use it for the actual knob.

 

So here's the surprising part: the model is hollow, with basically a baffle in the center for structure (running transverse left-right, straight up the axis of the stick).  I mostly wanted it to survive inserting the threaded sleeve, but ultimately the knob would be full of epoxy and lead so it doesn't need much internal structure.  With hard plastic all the little vibrations as transmitted directly; but with this rubber model, the internal structure makes it basically like a tennis ball.  I can squeeze it a little, or roll it forward/back a little, but it's PRETTY rigid.  Like I didn't notice the compliance until I was trying to figure out why it would shift so much better than the others.

 

So the accidental side effect: it is just a little bit compliant fore/aft, which soaks up smaller NVH when shifting up & down.  The effect is subtle, but has more benefit than adding 100g lead.  The surface is a little bit grippy, which isn't terrible.  It's not as smooth as the polished version but after a few minutes I kinda like it.  So now that I don't have to fill it with lead, I'm wondering if I should make a hybrid wood model with a compliant rubber sleeve...

[Davemk1]

Car makers have been smoothing out shifting with weighted knobs for a long time. It in effect it's a mass-damper that resists vibration. The extra mass also gives it more momentum once moving across the open gate so that it moves into the next gear with less force. It takes more force to get it moving but then it uses that force to move into the next gear.

 

I have a very light wooden knob on my Honda shifter and noticed it feeling a bit notchier than the stock alloy knob. I use it because on a hot, sunny autocross the metal knob can get really hot...but the wood feels much cooler to the touch. But the heavier alloy knob shifted a bit better.

 

dave

[Austin David]

so far, this one lucky shot seems to be the better of both options: it damps vibration through the various linkages, and doesn't get hot (or cold).  They're also pretty easy to make in this form, so if anyone wanted to try one (and can use M10-1.5 / Miata threads, or tap their own) I'd be happy to make extras.

[inchoate]

 

Got bored at work so I did a little research into the whole balsa wood shift knob thing.  We usually have balsa wood scraps lying around so I whipped one up.  I could probably get a little more weight out of it by lightening the aluminum threaded insert and making it a little bit smaller (it's currently 1.85" in diameter), but 17g is pretty darn light.

 

So if you want the lightest possible knob that's probably the way to go.

[Austin David]

how does it feel while driving?

 

I don't have a target weight.  if I wanted to save a few hundred grams I could leave my phone at home.  Having done some braining and some research I may try to fill it with silicone, which seems to be a good, inexpensive vibration dampener.  I wanted to test it in a Miata last week on a road trip, but the treads are 10x1.25 in the Miata, and 10x1.50 in my Caterham.

[inchoate]

I haven't given it a try yet but I'd imagine that it would be very notchy.  I made it more as "just to do it" kind of thing.