Make a 5-Speed Shift Knob the Old Fashioned Way - Page 5 - Rennlist - Porsche Discussion Forums



928 Forum
Sponsored by: 928 Specialists

Make a 5-Speed Shift Knob the Old Fashioned Way

Reply
 
Thread Tools Search this Thread
Old 03-12-2017, 06:29 PM   #61
Jerry Feather
Addict
Rennlist Member
Thread Starter
 
Jerry Feather's Avatar
 
Join Date: May 2008
Location: 2706 Skyline Drive, Grand Junction CO 81506
Posts: 3,995
Default

Quote:
Originally Posted by Bertrand Daoust View Post
You can also use a scale to do this.

- Put a bucket with water in it (at half maybe) on the scale.
- Tare (0) the scale.
- Then suspend the part in the water without touching the side or bottom.

The weight shown will be the water displacement (volume).

Use the smallest wire you can find to suspend the part to get as precise as you can.
If you don't have a scale you can tare, just take the weight with the part suspended less the weight of the bucket and water et voila!
Duplicate.
Jerry Feather is offline   Reply With Quote
Old 03-12-2017, 06:34 PM   #62
Jerry Feather
Addict
Rennlist Member
Thread Starter
 
Jerry Feather's Avatar
 
Join Date: May 2008
Location: 2706 Skyline Drive, Grand Junction CO 81506
Posts: 3,995
Default

Quote:
Originally Posted by Bertrand Daoust View Post
You can also use a scale to do this.

- Put a bucket with water in it (at half maybe) on the scale.
- Tare (0) the scale.
- Then suspend the part in the water without touching the side or bottom.

The weight shown will be the water displacement (volume).

Use the smallest wire you can find to suspend the part to get as precise as you can.
If you don't have a scale you can tare, just take the weight with the part suspended less the weight of the bucket and water et voila!
How does weight equal volume? What if the part floats? I think this will work, if at all, only North of 45 Degrees North Latitude.
Jerry Feather is offline   Reply With Quote
Old 03-12-2017, 08:10 PM   #63
Bertrand Daoust
Addict
Rennlist Member
 
Bertrand Daoust's Avatar
 
Join Date: Oct 2005
Location: Gatineau, Québec, Canada
Posts: 3,571
Default

It will work if it is completely immerse.
If it floats, you'll need to find a way to immerse it completely and deduct what you used to keep it under the surface.

The density of water is 1.
So one ml = 1g.

The volume the part takes will be equal the it's weight.
Edit: Not it's weight but it will be equal to the weight of the water displaced.

Last edited by Bertrand Daoust; 03-12-2017 at 11:17 PM.
Bertrand Daoust is online now   Reply With Quote
Old 03-12-2017, 08:19 PM   #64
Dave928S
Addict
Rennlist Member
 
Dave928S's Avatar
 
Join Date: Jun 2008
Location: Tasmania, Australia
Posts: 4,372
Default

Quote:
Originally Posted by Jerry Feather View Post
How does weight equal volume? What if the part floats? I think this will work, if at all, only North of 45 Degrees North Latitude.
A basic measurement principle in physics, with the moment of discovery attributed to Archimedes .... https://en.wikipedia.org/wiki/Eureka_(word)
Dave928S is online now   Reply With Quote
Old 03-12-2017, 08:45 PM   #65
Jerry Feather
Addict
Rennlist Member
Thread Starter
 
Jerry Feather's Avatar
 
Join Date: May 2008
Location: 2706 Skyline Drive, Grand Junction CO 81506
Posts: 3,995
Default

Quote:
Originally Posted by Dave928S View Post
A basic measurement principle in physics, with the moment of discovery attributed to Archimedes .... https://en.wikipedia.org/wiki/Eureka_(word)
OK, but there is no "Eureka" here! As suggested by Bertrand when, we suspend the object in the bucket of water and check the weight, the water, although now displaced around the object, is still in the bucket, so the weight of it will not change. The only thing that might change the scale reading is how much downward pressure one might be using to hold the object under, if it floats, and maybe a negative weight related to how much of the object is being held above the bottom of the bucket if it otherwise will sink. Neither weight indication is going to relate at all to the weight of the water displaced, since it is still in the bucket.

And maybe south of 45 degrees south latitude?

Last edited by Jerry Feather; 03-13-2017 at 12:33 PM.
Jerry Feather is offline   Reply With Quote
Old 03-12-2017, 08:51 PM   #66
Jerry Feather
Addict
Rennlist Member
Thread Starter
 
Jerry Feather's Avatar
 
Join Date: May 2008
Location: 2706 Skyline Drive, Grand Junction CO 81506
Posts: 3,995
Default

Quote:
Originally Posted by Bertrand Daoust View Post
The volume the part takes will be equal the it's weight.
I don't think so. The volume of the object will be equal to to weight of the water displaced.

How are you going to separate the water displaced from the water not displaced? Or otherwise measure it by itself.

Maybe doing what Randy suggested in the first place--with a graduated cylinder, or some similar substitute.
Jerry Feather is offline   Reply With Quote
Old 03-12-2017, 09:08 PM   #67
Bertrand Daoust
Addict
Rennlist Member
 
Bertrand Daoust's Avatar
 
Join Date: Oct 2005
Location: Gatineau, Québec, Canada
Posts: 3,571
Default

Just do what Randy suggest and you'll be fine.

We're not going anywhere here.

You can do whatever you want at the end... But my method would work.

Like Dave said, it's not mine, it's Archimedes!
Bertrand Daoust is online now   Reply With Quote
Old 03-12-2017, 09:29 PM   #68
Jerry Feather
Addict
Rennlist Member
Thread Starter
 
Jerry Feather's Avatar
 
Join Date: May 2008
Location: 2706 Skyline Drive, Grand Junction CO 81506
Posts: 3,995
Default

OK, I'll back off. I figured it out, but I haven't figured out why. I understand about Archimedes, but I can't figure out why the object suspended in the water appears to weigh the same as water no matter what it is.

I did a test to see if I could show what I thought was the case, with different density objects suspended in the water, and I found that You, Bertrand are exactly correct. I went out in the shop and found a chunk of 3/4 inch aluminum plate cut off of something and then cut a piece of wood to almost the exact same size. Then I suspended them each separately in a jug of water on my scale and they each show the same weight.

I'm not sure now what my scale is reading in, but when I figure that out I'll know what one of my ***** volume is. Here are some pictures of the test.
Attached Images
     

Last edited by Jerry Feather; 03-12-2017 at 09:55 PM.
Jerry Feather is offline   Reply With Quote
Old 03-12-2017, 09:54 PM   #69
Jerry Feather
Addict
Rennlist Member
Thread Starter
 
Jerry Feather's Avatar
 
Join Date: May 2008
Location: 2706 Skyline Drive, Grand Junction CO 81506
Posts: 3,995
Default

Here's the GTS mold full of molding compound in the upper half of the mold. I think it poured much better than the other one and I'm pretty sure it'll open without any bubbles.
Attached Images
 
Jerry Feather is offline   Reply With Quote
Old 03-12-2017, 10:08 PM   #70
Jerry Feather
Addict
Rennlist Member
Thread Starter
 
Jerry Feather's Avatar
 
Join Date: May 2008
Location: 2706 Skyline Drive, Grand Junction CO 81506
Posts: 3,995
Default

Based on Bertrand's revelation and my proving it to myself, I found that the early shift **** displaces .158 or so pounds. That comes out to 71 grams or 71 ml. When I get the GTS **** out of the mold I'll measure it the same way and then know almost exactly how much rubber compound to put in the 100 ml syringe. Thanks Bertrand. Sorry about all my ignorance.
Jerry Feather is offline   Reply With Quote
Old 03-12-2017, 10:29 PM   #71
Bertrand Daoust
Addict
Rennlist Member
 
Bertrand Daoust's Avatar
 
Join Date: Oct 2005
Location: Gatineau, Québec, Canada
Posts: 3,571
Default

The shifter shown here that weight .156 pound is 4.27... square inches. Less the wire that you use that is inside the water which I would not worry here.

Keep up the good work Jerry.
Bertrand Daoust is online now   Reply With Quote
Old 03-12-2017, 10:39 PM   #72
Bertrand Daoust
Addict
Rennlist Member
 
Bertrand Daoust's Avatar
 
Join Date: Oct 2005
Location: Gatineau, Québec, Canada
Posts: 3,571
Default

Quote:
Originally Posted by Jerry Feather View Post
I don't think so. The volume of the object will be equal to to weight of the water displaced.
Right Jerry.
Bad phrasing. Sorry.
I edited my post.

No need to be sorry Jerry.

Not at all.

Again, keep up the good work.

Last edited by Bertrand Daoust; 03-12-2017 at 11:15 PM.
Bertrand Daoust is online now   Reply With Quote
Old 03-13-2017, 01:32 PM   #73
Jerry Feather
Addict
Rennlist Member
Thread Starter
 
Jerry Feather's Avatar
 
Join Date: May 2008
Location: 2706 Skyline Drive, Grand Junction CO 81506
Posts: 3,995
Default

And there it is--freshly opened and a perfect mold of the upper half of the GTS ****. As with the first half, the wooden extension I had glued onto the bottom end stayed in the mold, but it has release on it so it will come out pretty easily by picking with a small chisel. Then I can smooth the transition with the chisel and files. The four round registration bumps I put in it also came or perfect.
Attached Images
  
Jerry Feather is offline   Reply With Quote
Old 03-14-2017, 12:24 AM   #74
Jerry Feather
Addict
Rennlist Member
Thread Starter
 
Jerry Feather's Avatar
 
Join Date: May 2008
Location: 2706 Skyline Drive, Grand Junction CO 81506
Posts: 3,995
Default

The weight of the water displaced by the GTS **** suspended in the water in the jug is .210 pounds. That is with the 3/4 inch extension broken off. I think that means that it is going to take something over 100 ml of rubber compound to cast it. What that means is that I'll need to mix up just under 200 ml of compound, then start with the original **** and inject its mold first from a full 100 ml syringe, then use the rest of the syringe into the GTS mold, then finish the GTS mold with another nearly full syringe of compound.
Jerry Feather is offline   Reply With Quote
Old 03-14-2017, 09:54 PM   #75
Jerry Feather
Addict
Rennlist Member
Thread Starter
 
Jerry Feather's Avatar
 
Join Date: May 2008
Location: 2706 Skyline Drive, Grand Junction CO 81506
Posts: 3,995
Default

It seems to calculate out that it will take nearly one pound of rubber compound to form two each of these shift *****. I have one pound and it costs nearly $50 on eBay. There is a better source online for 10 pounds for $344 including shipping. If this stuff works out with what I have I'll order that.

After I get the casting of ***** refined, to the extent that it isn't yet, then I'll have another effort to complete in making a somewhat similar set of forms to assist with the covering these with leather in much the same fashion as they were done by or for the factory.
Jerry Feather is offline   Reply With Quote
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Replacement shifter boot for GTS 5-speed? SQLGuy 928 Forum 7 03-20-2017 10:01 AM
"997 shiftknob to 968" cosmetic update -- so easy a caveman could to it... odurandina 968 Forum 9 05-23-2016 07:36 PM
5 speed shifter boot base loose prescott 928 Forum 6 03-03-2016 12:01 PM
TWM Weighted Shift Knob - Installation and Review KoB 996 Forum 10 01-16-2015 12:03 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump


All times are GMT -3. The time now is 07:57 AM.


Copyright © 1998 - 2017 Rennlist.com
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: