Alfa Romeo Forums banner

Rear bumper rubber spacers

19K views 167 replies 27 participants last post by  EdBorto 
#1 ·
Here is my original message posted at Montreal Parts (johni6020) thread:

"Two steel molds are being developed and I expect to get a pair for my car and put the rest here for selling at cost which is US$30 a set (4 units) just to get the molds payed. I am planning to use EPDM and be ready early September. I will run some tests in my car bumper using 3D printing prior to final prduction"

So far I received 20 sets confirmation - each set contain 4 units - which means I am moving forward.

Thank you!
 
#6 ·
Thank you for your interest in the rubber spacers. I am sending PM to each one of you and I will keep you informed about the progress of this project. There is no need to send any payment at this time.
 
#10 ·
Just to let you know I have the digital Solid Works drawings and will 3D print using FLEX polimer. If it works fine next week the two molds will be manufactured and in the week of Sept 3rd the final parts injected using EPDM material. Any suggestion is welcome at this time because this a cocreation process. Please notice that the peripheral cord is 5mm in diameter while the rubber spacer thickness is 3mm. If you feel these dimensions should be adjusted please let me know.
 

Attachments

#11 · (Edited)
Hi Edgar,

Thanks for your work on this project. The inside 'web' shape part of the gasket looks good. I suspect the web portion is only 1 or 2 mm's thick, at most. Unfortunately I've already put my gaskets back on the car and did not take any measurements.

However, the shape of the exposed gasket part (the part seen when the bumper is installed on the car) that covers the gap between the bumper segments appears to have the wrong profile in the attached drawing. I measured the best gaskets on my car and the exposed part measures ~8 to 10 mm wide, although some appeared to have shrunk and curled up some. The profile of the exposed part of the gasket is more the shape of a flattened out "D" on my parts.

Here is a link to some pictures of the bumper gaskets on my car. I hope this helps. If you have any questions, please let me know.

https://www.alfabb.com/bb/forums/alfa-romeo-montreal/564658-rear-bumper-rubber-spacer-gaskets.html

Here is a photo of the exposed gasket that measures 10 mm wide.

Hand Finger Arm Wrist Measuring instrument


Mark
 
#16 ·
Hi Edgar,

Thanks for your work on this project. The inside 'web' shape part of the gasket looks good. I suspect the web portion is only 1 or 2 mm's thick, at most. Unfortunately I've already put my gaskets back on the car and did not take any measurements.

However, the shape of the exposed gasket part (the part seen when the bumper is installed on the car) that covers the gap between the bumper segments appears to have the wrong profile in the attached drawing. I measured the best gaskets on my car and the exposed part measures ~8 to 10 mm wide, although some appeared to have shrunk and curled up some. The profile of the exposed part of the gasket is more the shape of a flattened out "D" on my parts.

Here is a link to some pictures of the bumper gaskets on my car. I hope this helps. If you have any questions, please let me know.

https://www.alfabb.com/bb/forums/alfa-romeo-montreal/564658-rear-bumper-rubber-spacer-gaskets.html

Here is a photo of the exposed gasket that measures 10 mm wide.

View attachment 1522264

Mark
Mark, thank you for your comments and ideas. I still have the original rubbers but they are not reliable to take any measurement due to the poor conditions. We agree to change the circular exposed segment diameter from 5mm to 10mm and also its shape, adopting the "D" for the straight bumper joint. We will run a 3D printing test for both models and send some pictures. My car bumper is out so is easy to do it.

Thank you again!
 
#14 ·
Rear bumper rubber spacer

Hi edgar!

I will take 2 sets = 8 pieces for my 2 montis.
Greetings and thank you for your Engagement in remanufacturing .
Gernot
Thanks for supporting this project Gernot! Will send you a PM.
 
#13 ·
Hi Edgar,

A couple of things are probably apparent from the attached sketch. Unlike Paulo Labres, who has mad computer skills, I have none. Secondly the "flattened D" shape of the exposed gasket is attached to the 'web' area -tightly compressed between the bumper segments.

On my original gaskets, the rubber shrinkage was so significant it resulted in the exposed 'D' shaped gasket retracting between the bumper segments. This was similar to a turtle pulling his head back into its shell. Once the bolts that hold the gasket segments in place were removed, I was able to reposition the gaskets so that they covered the joints between the bumper segments again.

Drawing Sketch Cylinder Artwork


Edgar, do you have a set of original bumper gaskets or are you working mainly using the bumper profile?


Mark
 
#18 ·
Hello Danny, can you get close pictures from the straight and the upper corner exposed rubber sections? Can you measure to confirm aproximate diameter of 10mm? Thanks for offering to send the part but I think we don´t need it in this moment.
 
#17 ·
My pleasure Edgar. I wish that I had taken measurements while the gaskets and bumpers were off my car. I am glad you were positively receptive to the suggestions. I had hoped that others would add their comments or suggestions as well.

The material originally used by the factory for these gaskets has an alarming shrinkage rate. This was probably exacerbated by my cars long term storage in a hot storage unit in Arizona. I don't think there would be similar issues with the use of EPDM or I would have suggested increasing the diameter of the bolt hole, since it tended to trap the gasket in position, pulling the rest of the shrinking gasket inside the bumper seams.

Mark
 
#19 ·
Rear bumper rubber spacer




Mark, thank you again for the comments and suggestions. Yes, I agree about the original material. During the restauration I tried to use a material called "plastic debrum" very popular in the 60´s and 70´s cars to cover the space between two body metal parts. But it did not work.
 
#20 ·
I would like to report that Alfa has corrected issues with their rubber but this is not the case. Currently the 1992, 164-S that I purchased when it was new, is being refurbished. The rubber shift bellows for the gear selector on the transmission has turned to hard broken chunks of rubber, several of the plastic electric connectors are deteriorating and falling apart. I'd like to think that things are better now for the 4C, Giulia and Stelvio but I wonder if anything has really changed. Italians must take a lot of pride in being metallurgists; to be a polymer engineer must not be considered as an important career.

Mark
 
#22 ·
Danny, in the TAV.129 part list page I am seeing only the left side indication as follows: upper corner rubber 105.64.59.490.00/02 and botton straight bumper spacer 105.64.59.490.00/01. There is no indication of these parts at all in the right side. If you are seeing something different, like 4 part numbers, please let me know.

The "set" we are developing comprises two rubbers for the left and two for the right side. So, with one set you are ok for the entire rear bumper.

I am planning to upload the first 3D parts this evening so we can check together how it fits.
 
#26 ·
What a find Danny! Yes, VIPLA is a well known material. BTW plastics in the 70´s were just starting after second WW developments of Catalin, Bakelite and Plaskon.

Here is the first 3D run of the two parts made out of a rigid plastic printing thermoplastic filament called PLA (Polyactic Acid) which is made out of sugar cane in Brazil and for this reason is biodegrable.

I expect to make corrections including the proposed 10mm exposed region and generate a second set of parts but printing in a different material which is flexible, called FLEX.

For comparison there is a 8mm diameter pencil.

Mark, I will install these PLA parts in the real bumper tonight and send pictures for your evaluation.
 

Attachments

  • Like
Reactions: IRONBLOCK
#31 ·
Rear bumper rubber spacer



This is an interactive time consuming task that will pay off because we will reach a better result. Not just another repro but the best one.
 
#32 ·
Rear bumper rubber spacer



TAV.128 shows two different parts, left and right. I never had a part like this in my hands before. I will need pictures from a real part to make an evaluation. I propose we finish the bumper rubber spacer and then we start another thread for this one. Maybe Mark could bring some ideas about that part. Is it available anywhere? What do you think?
 
#28 ·
Hi Edgar,

Those parts are exciting to see. Is there a flattened D in cross section; I can't tell from the picture.

You are right there are only two different gaskets for the rear bumper:
one for the upper rear corners
one at each end of the lower center part of the bumper.

All four gaskets appear to be made of the same material. I found another photograph I took of the upper rear bumper gasket which sort of conforms to the shape of the bumper. There is a tight 'inside corner' that honestly leaves very little room for the gasket, so it tends to get distorted.

Bumper Automotive exterior Vehicle Auto part Car


Mark
 
#30 ·
#33 ·
Here are the two initial pictures of the demo part in place:

Material: 3D printing PLA rigid
Thickness: 3mm
Exposed rubber: Circular shape with 5mm diameter

What do you think?


The next 3D demo will be:

Material: 3D printing FLEX flexible
Thickness: 2mm
Exposed rubber: "D" shape with 10mm

We expect to close the project with the second demo so next week we can produce the molds and inject the final parts using EPDM.
 

Attachments

Top