79 Eldorado Biarritz: Trip OD Repair -Speedometer Needle Removal question

[79 Eldorado]

Hello All,
I have a 1979 Eldorado and since I’ve had it the trip OD has never worked. Well the heater core went bad the other day so while I was changing it I thought it would be a good time to look into the trip odometer. The good news is I quickly discovered the problem; a broken trip OD drive gear. Now the challenge is fixing something that I look at every time I drive without damaging it. At first I couldn’t figure out how to remove the trip odometer extension because the service manual was a little vague without a graphic but I figured that part out and I will post some supporting photos. The next step appears to be removing the speedometer needle. I’m not a novice to delicate nature of ‘80s style speedometers and so I want to ask before I break something due to an incorrect assumption. Is the needle removed by gently prying under the needle itself or is there some other type of release mechanism? I saw a short youtube video where they used 2 spoons which seemed like a good idea.

Any advice or insight is appreciated
Thank you,
Scott

BTW The heater core replacement went smoother than I expected. I was able to move the dash/ instrument panel assembly back far enough on the passenger side that it did not need to come completely out of the car. Finding a replacement Copper/Brass core seemed nearly impossible but I finally found what appears to be a NOS part.

[79 Eldorado]

Ok well I looked at a lot of other photos of speedometer needles and it seemed the needle normally has a barrel which presses over a pin. For that style the 2 spoon method I saw someone on youtube use seemed appropriate and so I tried it. It worked. I won't start smiling yet because it needs to be fixed and it needs to go together without breaking anything. After taking it apart I also see there is a clip which slides in to hold the pin in place.

Interestingly the axle/shaft/rod which runs from the main OD to the trip OD which was missing the broken gear on one side also has the same PN gear on the other side. I didn't notice it at first but I took a photo to post and it looks like the other gear has a hairline fracture. Take a look at the photos.

[TMoore - NTCLC]

This is great information, and I would bet that a lot of the speedometers from that ears may be similar - thanks for taking the time to post this - I am sure it will come in handy one of these days.

[79 Eldorado]

No problem. I was hoping to have some insight from others but knock on wood things have gone pretty well so far and if it helps someone else out in the future that would be great. It's not easy to find parts for older cars so the fewer parts we break while trying to repair them the better. I tried searching for the broken gear and I couldn't find it. I believe it's nylon and I have a few ideas regarding repair but this is one situation where I won't get multiple tries if the attempted repair makes matters worse (distorts the shape for example). It also seems like a great application for 3D printing. Even the local Libraries around here have a printer now. The teeth on this gear don't seem to be something easily found in reference but I'm trying to take enough measurements to recreate it if repairing does not work.

I will list some of the measurement below. I measured metric and English separately in most cases as opposed to converting measurements. Having had three 1979 E-Body cars I know that these cars are heavily metric but you can still run into parts which are based on English standard so it's always difficult to tell what you will encounter. The point being if you find gear dimensions which seem to closely align to common numbers in one system or the other you can possibly tell which way to round things because designers like round numbers.

39 Teeth
OD: 21.63mm (0.850”)
Ring thickness: 2.11mm (0.083”)
ID: 3.05 <<Make smaller to drill to fit (0.120”)
Total thickness: 4.8mm (0.190”)
OD of hub: 9.35mm (0.355”)
Circumference at OD: 67.953mm (2.6704”)
Tooth pitch: 1.7424mm (0.0685”)
Approx diameter at root of teeth: 19.08mm (0.750”)
Approx tooth height: 1.275mm (0.050”)

OD needed to result in 1.75mm pitch: 21.725mm <<Thinking if it was metric it may have been designed to be exactly 1.75mm.

Hub is the same diameter and size on both sides of the main gear. The size measured above is at the “top” of the hub or farthest from the main gear. There is a small amount of draft meaning the hub diameter at the main gear is slightly larger; likely 2-3 degrees of draft.

[79 Eldorado]

Still working on this. Here is an additional measurement of the tooth angle. That angle is influenced by the OD, the root diameter plus the tip and root radius. I concluded it was about 52-53 degrees upon taking some additional measurements after the ones shown here. It even looks like it has a clocking mark; possibly to try to align the teeth from the same portion of the mold?

Edit: Unless what I think is a clocking mark is a 1 for cavity 1...

[79 Eldorado]

I had some help but we recreated the design and then 3D printed it. The broken gear is now replaced. The gear as printed had a few teeth on one side plugged near the gear face but a small file resolved that issue (3 to 4 teeth total where the surface of the gear bled into the teeth).

We designed the replacement with 0.120” center hole. The shaft is 0.125” or 1/8” but with a knurled spline. I expected and wanted it tight because it’s easier to enlarge the hole… I ended-up heating the copper colored rod, holding with a paper towel, and then while hot I slid it through the center of the new gear. Once it was cool it was very tight. One thing though be very careful to not insert too far as I did because the right and left supports for the shaft require a minimum distance which is extremely close to the normal installed position. I could not assemble it at first try. I was able to slide the new gear down the shaft by using a fork to span the shaft/rod pushing on the fork to distribute the push over more of the gear evenly.

I started to remove the unbroken gear but then I stopped because I was applying a lot of force and it didn’t move. Based on that I thought it may last and if it does not I will replace it later. If I hadn’t been working on this so late at night I may have made a different decision.

To remove the shaft with only the right hand gear I didn't need to remove or loosen the OD or Trip OD but once the two gears were in place I needed to temporarily slip the OD portion out. That was very easy. You need to lift up on the clip on the left side of the OD; no prying required as it just lifted off easily. Once the clip is off I slid it left to clear the right side support hole, moved the right side towards me and then slid the left side out.

To assemble the shaft once the OD was removed I started on the left side and slipped the rod under the left support. The right side goes in in one direction/axis. Once the shaft was in I was able to slide the OD back in place and replace the clip. I cannot recall if I pushed the right side of the axle in before or after the OD was back in but allowing it to be free allows you to change the position of the rod while the OD is inserted. I would say just don’t force anything because once you figure out the motion you should not need to force anything.

The speedometer needle just pushed back on but it was such a non-event I’m not 100% sure I fully seated it. I think so but the next time I would have taken a depth measurement with calipers before removing it.

Scott

[bcroe]

Nice work, looks like you are now in charge of solving all speedo gear problems. 
Bruce Roe

[79 Eldorado]

Thanks Bruce. If someone needs a gear I could send the "STL" file which is the file format popular for 3D printers. A friend printed this one for me but there are at least two local Libraries not too far from here and each has a 3D printer. They give a free class and they charge only for the plastic used. I suspect the same is true in other areas. I would have the confidence to repair one for someone but it seems like there is a lot of risk in shipping something like that.

While I was removing the applique panel around the stereo I noticed someone previously over tightened the top 2 Philips head screws and cracked the outer surface and the ears where the  screws go through. I decided to try a repair with a Polyvance plastic welder and some ABS plastic rod I found on Amazon. The Polyvance welder came as a kit with some stainless mesh like door screen. I first stitched cracks, from the back,  where I saw them and then I built the area up on the back of the panel. I then I placed a small piece of screen on the back. While holding the screen with a needle nose I used the welder to melt the screen into the plastic. I then went the front side and placed a short piece of ABS rod on the screen and melted it in. It worked very well. The only thing I would say is that you may need to "drill" the holes again. I made the mistake of actually drilling. The first one worked but the second one cracked a bit when the drill bit caught the screen. I learned from that though, repaired the area a bit, and instead of drilling I heated the drill bit and melted-in the position with the hot bit held in a channel lock. I believe if the screen was an issue the point of the screw may guide the screen out of the way whereas the drill caught it and tried to twist it. I took some photos so I will upload them later. I still need to paint the front side edge. I would also say that if all of the pieces are there it is possible to join the existing pieces from the back with the welder.

I bought Polyvance kit 5210 but I used ABS rod and not the filler in the package. I've now repaired polypropylene, polyethylene and ABS but all using the same filler as the original part.

Scott

[79 Eldorado]

Photo of panel ear repair.

[79 Eldorado]

Updating as there is some good related information in the thread below from Rick "Cadman-iac". It includes photos and a detailed explanation regarding how the segments of the barrel and the gears between the segments look and function:

http://forums.cadillaclasalleclub.org/index.php?topic=159596.0

Scott

[Cadman-iac]

Scott,
That's some pretty impressive work on making a new gear, very technical. I know I wouldn't be able to figure out how to make a new one. Probably requires a lot of math too. Not one of my strong suits.
  Can I call you if I need something made?

[79 Eldorado]

Rick,
If you need something you can contact me and I will try to help.

A lot of the time is often required to make certain your measurements are correct before you even start on the next step. To measure the gear I started by taking a photo and then I blew it up as much as I could on a copier. I then used a protractor. I really think that the original gear wasn't even perfect so then you need to decide which measurements are the ones to use. I measured the height, angle, root and tip radius on several teeth and then I just used my judgement.

Some parts are easier than others. I'm working on the FIV (Fast Idle Valve) now for the 70's EFI. So far that's taken about a year but not all active time. I've been researching the different aspects of it, looking for component parts and ideas for modern substitutions. Once I find something which seems to work theoretically I then need to figure out how I can get the part. Bruce Roe on this site has been a lot of help. He donated a couple of used FIV's and a spare throttle body. Those were very helpful because it's amazing how many times you need to go back and verify a measurement or test fit something. I don't know if I would have been lucky enough to take the parts off my functioning car that many times without breaking something.

Did you have a part in mind?

Scott

[Cadman-iac]

No, not at this time.  But i will definitely keep you in mind if and when I ever do need something made. I had considered buying a 3D printer at one point,  but I just don't know enough about them, and about what is necessary to make it work for me. It's another one of those deals where you have to decide what you want to spend your time and money on.
I'm like you I think,  I know I have way too many projects going and a limited amount of time and money. So I am going to have to figure out what I want, and what I need, and what I can do without, and go from there.
Thank you for the offer, it's greatly appreciated. And good luck on your valve project.  I hope you can make it work. I'd like to see it when you get it done.

Rick

[79 Eldorado]

The first 3D part I had printed was done at a local library. There's a 3D printer, small build volume, in each of two small towns not far from me. They even printed the first one for me after I provided the "STL" file. The second one I did myself at the library. I had help with the gear. It was either just before I bought my printer or if after a friend offered to print one (the teeth were pretty fine and I wasn't sure how well it would print). When I finally bought my own first printer I decided before buying it that it would be mostly for test fit parts. I had a couple of specific bent metal parts in mind before buying it. The initial measurements on those parts were really difficult to measure. In fact one of which I only ever had photos to go from but I have the mating part. I still haven't quite finished that project because I am off slightly and there are two different ways it could be corrected but without having ever had the real part it's nearly impossible to tell what should be altered.

I have printed a few functional parts especially if you count the ones a friend printed for me before I was set-up:
- The rubber connector on my coolant temp sensor was printed with TPU material and 2 of the 3D printed parts are on my own car. Thanks to the help of a member I realized that the originals were still available. At the time I found out I was already in the process of designing the mold.  I reverse engineered the connector and I was considering having it tooled.

- A sprinkler head for a watering can my dad had. The head was missing for years and it seemed to be an odd size.

- Interior door trim covers for the end of the pull handle which is riveted at both ends. Terrible sliding snap design which breaks really easily.

- A microwave door open button for my parents' microwave. The original had a snap looking catch which stops the button when it pops back under the load of a spring. That was difficult because it was an actual snap which needed to flex to be assembled but not really after. I redesigned it to extend the snap farther toward the face but one side always broke off due to the layers. My layer adhesion is good but it wasn't the best snap design to begin with. I wanted the face which people see to be glass smooth. It was glass smooth with that surface printed on my heated glass bed so I couldn't turn the entire button and still keep the mirror like original finish. So for the snap portion I modeled a second piece which slid over the 3 cylinders which guide the button. One of those cylinders also has the return spring on it. Anyway I was able to further improve the flex of the snap arm and just as important I was able to print that part laying down on its side so the layers were not in the direction which would easily break when it flexed. It really turned out incredible. It's not really possible to tell the difference between the replacement and the original. Giving credit to my mom she placed a piece of Gorilla tape on both ends of the button which stopped the button from flying out. So she MacGyvered it to work but it didn't look as nice

- I started working on some of the either hard to find or poorly designed interior clips for my Eldorado and Toronado as well. The ones which hold the metal molding on the sides of the headliner are nearly impossible to assemble. I want to design a replacement with enough flex to allow easier installation. I replaced the headliner once in the Toronado and it needs another. The thing stopping me is knowing what a horrible and risky job it is removing the surrounding trim pieces.

- Oh and we had an old Wilton vice at work which somebody cannibalized the jaws of. They had been missing for years and you could tell the vice saw a lot of work in its lifetime. We measured the jaws and we printed a set out of very basic PLA. We work with mostly Aluminum and Cu parts but those PLA jaws have been on that vice for over a year now. There are a couple of nicks in them but they are still in very good shape. We don't beat them with a sledge hammer but we're not that easy on them either. Our intent was to have some made but after using these we never did (actually probably available on Amazon but it is a very old vise). With our parts if we squeezed any harder we would damage the parts we are working on so the PLA jaws give us a little factor of safety... although even those will crush some of the parts.

In the General topics within this forum there's a 3D printer topic which started recently Mitchell made some really nice filler pieces which go under the headlights near the top of the bumper. He mentioned them once and I thought he was talking about some of the large very flexible parts. The aftermarket ABS and sometimes fiberglass replacements are not easy to fit and they aren't as flexible. I was wondering how TPU would work but TPU would be difficult to finish. It's like a high durometer rubber.

Scott