78 wiper linkage - I've joined the club

[Big_John]

It looks like @HombreCalgarian hasn't been on since June. Click on his user name and you'll see that.

You guys might want to try messaging him and he might get a notification email.

 

[Dobalovr]

I reached out to him to join our little group but no response.

 

[73 T&C]

Previous owner of my car cut off the offending part and replaced it with one from a Cordoba. Works great.

if you want see it go to my very long post.

 

[HombreCalgarian]

Hey Hombre,
I know AutoCad. Would you consider sharing your drawing and I will turn it into a 3d drawing and post it here. I also have a 3D printer here in Kansas City that will make them for me. Not sure on the material, but they assured me it was tough enough for car parts. I will find out more details and post them here.

Hey,
For some reason I never got the updates to this post (or my spam filter went berserk) and missed you message. My apologies. The sketch is long lost, I'd have to disassemble everything again to replicate the work. I might find the original part and try to measure it again and put it on the paper. Just need time to do this - and it is house updates time... Anyhow, better reach me via personal messages, I guess.

 

[mantlewearer]

I have this same "78 wiper failure" problem, I don't see on here if anyone ever posted the autocad for a replacement bushing? I have access to a 3D printer capable of printing the part if I can get a pattern. Thanks!

 

[HombreCalgarian]

I have this same "78 wiper failure" problem, I don't see on here if anyone ever posted the autocad for a replacement bushing? I have access to a 3D printer capable of printing the part if I can get a pattern. Thanks!

Looks like noone ever tried to. Now thinking of it, I'd say it would be better if somebody made a drawing of the pre-78 all-metal part, as it is a dead reliable and robust solution as opposed to another plastic part. Also thinking of the 3D-printed one, I am not entirely sure if the durability of the printing material will be on par to the task.

 

[mantlewearer]

Looks like noone ever tried to. Now thinking of it, I'd say it would be better if somebody made a drawing of the pre-78 all-metal part, as it is a dead reliable and robust solution as opposed to another plastic part. Also thinking of the 3D-printed one, I am not entirely sure if the durability of the printing material will be on par to the task.

I have access to a 3D printer that can do "automobile quality" with carbon fiber.
But I agree that if there was a drawing, pics, or a pattern a machined one would be even better.

 

[Jeff Henry]

My take at solving the dreaded 78 linkage insert problem. Should admit it is not for everybody.
Pros - does not need donor parts.
Cons - Requires time, patience and lots of tools.

My solution was driven by time constraints (driving season is here and it is short), no access to 73-77 donors (methinks this retrofit would have been the easiest and the most elegant solution from engineering standpoint) and no immediate access to a welder. But I had access to a lathe, my own drill press and a dremel with multiple attachments.
As for the material for a new bushing, after some research and consultations I bought a foot-long 1.5" OD acetal bar for less than 20 bucks.
Why acetal? It is tough, easily machined to a great precision, is self-greasing, resists wear, and is hydrofobic.
From a website: Due to its low moisture absorption rate, Acetal’s physical properties remain constant in every environment, resulting in an ideally suited and stable product for close tolerance mechanical parts and electrical insulators. Acetal is designed to resist damage from most chemicals and solvents. In high moisture or submerged applications, Acetal bearings outperform nylon 4-to-1.
Next best - UHMW, third best - extruded nylon.

I dusted off my draughtsman skills (I am an old-school paper/pencil type, can't do it in AutoCAD) and after some caliper-twisting cobbled up a drawing for the machinist. Machining the external shape did not take much time. But the rest took much time to plot, mark, carve, drill and tap - especially since the friendly machinist is 1,5 hours away and I only had 1 linkage to play with - I did not want to err on anything.
View attachment 464771

View attachment 464772


View attachment 464773

First test-fit:
View attachment 464774
I figured that no matter how I try to replicate the snap-on lock of the original part, with available tools and skill level it will not be a reliable solution. So to maintain the bushing seating on the motor shaft I drilled the shaft and tapped it to accept an M4 hex head bolt.
View attachment 464775
Note to anybody who decides to go the same route - the shaft is hardened on the surface to a point when any drill bit will not leave a trace on it no matter how you try. I managed to carve through this shell only with a carbide dremel burr. But then to finish the hole you still need the best available "cobalt" bits. I went through at least 4 milwaukees before I was done.
And go extremely easy with the taper tap. Lots of oil, one cutting revolution at a time, then back off, clean, oil, repeat. You do not want the tap to snap in there.

Since the bolt has to move in relation to the bushing, I put an extra nylon washer between the bushing and the steel washer.
So far it runs well.

Hey Hombre,
Can you share your drawing with me? I know Autocad and can create a digital file so these hard-to-find cams can be 3D printed. I am happy to pay for your time and the drawing.

You can also reach me at jeffh@agencyh.com

Thanks in advance for your help!

 

[Fred A]

My take at solving the dreaded 78 linkage insert problem. Should admit it is not for everybody.
Pros - does not need donor parts.
Cons - Requires time, patience and lots of tools.

My solution was driven by time constraints (driving season is here and it is short), no access to 73-77 donors (methinks this retrofit would have been the easiest and the most elegant solution from engineering standpoint) and no immediate access to a welder. But I had access to a lathe, my own drill press and a dremel with multiple attachments.
As for the material for a new bushing, after some research and consultations I bought a foot-long 1.5" OD acetal bar for less than 20 bucks.
Why acetal? It is tough, easily machined to a great precision, is self-greasing, resists wear, and is hydrofobic.
From a website: Due to its low moisture absorption rate, Acetal’s physical properties remain constant in every environment, resulting in an ideally suited and stable product for close tolerance mechanical parts and electrical insulators. Acetal is designed to resist damage from most chemicals and solvents. In high moisture or submerged applications, Acetal bearings outperform nylon 4-to-1.
Next best - UHMW, third best - extruded nylon.

I dusted off my draughtsman skills (I am an old-school paper/pencil type, can't do it in AutoCAD) and after some caliper-twisting cobbled up a drawing for the machinist. Machining the external shape did not take much time. But the rest took much time to plot, mark, carve, drill and tap - especially since the friendly machinist is 1,5 hours away and I only had 1 linkage to play with - I did not want to err on anything.
View attachment 464771

View attachment 464772


View attachment 464773

First test-fit:
View attachment 464774
I figured that no matter how I try to replicate the snap-on lock of the original part, with available tools and skill level it will not be a reliable solution. So to maintain the bushing seating on the motor shaft I drilled the shaft and tapped it to accept an M4 hex head bolt.
View attachment 464775
Note to anybody who decides to go the same route - the shaft is hardened on the surface to a point when any drill bit will not leave a trace on it no matter how you try. I managed to carve through this shell only with a carbide dremel burr. But then to finish the hole you still need the best available "cobalt" bits. I went through at least 4 milwaukees before I was done.
And go extremely easy with the taper tap. Lots of oil, one cutting revolution at a time, then back off, clean, oil, repeat. You do not want the tap to snap in there.

Since the bolt has to move in relation to the bushing, I put an extra nylon washer between the bushing and the steel washer.
So far it runs well.

Hello, Is this still working? Are you able to make another one.

 

[Fred A]

Hello all,
Have not posted anything here for quite some time - there was not much to report, really. We just drove around without any issues. Did a winter run in December in between big snowstorms before Xmas. Chinook cleaned and dried the roads. So it was still a bit nippy, but dry.
View attachment 460124

Old Mopars can do ice-skating
View attachment 460125

A couple weeks ago Wife took the car a wee bit above 150 km/h indicated (about 95 mph in imperial money). Reported later the car was smooth as butter and very stable.

Yesterday I took the car to a car wash to remove the bug cemetery from the front. During the final wipe-off the wipers stopped midway, accompanied by a clunk from where the linkage is.
View attachment 460126
Further inspection at home revealed this. The left arm just fell off the motor, hence the clunk.
View attachment 460127

View attachment 460128
So I assume the 78 big cam disease struck me too.
As a permanent fix willing to go the 74-77 mod route.
Can some(C)body help out with the 74-77 donor parts? Actual parts, or pointers where to buy/source?
View attachment 460129

And finally - is there a way of putting the engine hood in a service position of a sort, old Mercedes-like? Like pulling both 'legs' forward past the notches and raising the hood at the same time?

Thanks a lot for all tips and answers.

Hello, I have the same problem. How did you fix?