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!
 
#38 ·
Edgar, the part looks excellent! I look forward to seeing the other part for the upper corner joints.

Alain says: (about the upper corner joint)
The width of the D-shaped part on Mark's picture reads 8 mm. I have measured on my car and it's 8 mm too.
Why not use this dimension for the next demo part?

Alain, I suspect that both parts initially had the same 10 mm wide 'D' shaped molding and after installation this dimension changes to 8 mm due to the curvature of the part. Alfa would typically make similar parts like this with the same profile.

Regarding the front bumper, there is only a much smaller rubber gasket that just covers the bottom of the 'banana'.

Mark
 
#40 ·
While searching for a picture of the banana base rubber gasket I found the following that may be helpful.

The banana gasket is rather thin (I would guess the exposed part is about 4 mm) but can be seen in the last two pictures at the end of this thread (since they are difficult to see, I'll take some close up pictures. If you have a Montreal parts book you can see this gasket there as well):

https://www.alfabb.com/bb/forums/alfa-romeo-montreal/661105-how-take-front-end-parts-apart-2.html

Also, the rear bumper is really not all that difficult to remove, once you find the hidden bolts as shown in this thread:

https://www.alfabb.com/bb/forums/alfa-romeo-montreal/587442-montreal-rear-bumper-removal.html

Well done Edgar!

Mark
 
#43 · (Edited)
Thank you for all feedbacks, comments and suggestions. Here are the next rendering pictures. We have made small corrections to better fit the bumper shape and the exposed region now moved from 5mm to 10mm diameter. We also changed the exposed region from a circular to a "D" shape format, following Mark´s suggestion. I think the "turtle head" format is the right one and will cover much better the space between bumper sections.

So, you can notice that the spacer for the lower straight section is ok. We can move to full 3D FLEX final printing and EPLD injection. We don´t expect any surprises in this spacer.

Now, for the upper corner spacer we will need to adjust the top and lower angles. We can not use the same "D" shape (180 degrees). The real angles are around 75 degrees (black lines).

Let´s move ahead. We are very close now.
 

Attachments

#46 · (Edited)
Thank you Danny!

Here is the upper corner spacer design we will 3D print for testing in the real bumper. It has 10mm modified "D" exposed region and adapted angles to perfectly fit the interface between the two bumper sections.

If it works perfectly this model will be the final injection mold fabrication template.
 

Attachments

#52 · (Edited)
Here are the pictures of the new spacers made in 3D printing using a flexible filament called FLEX and installed in the rear bumper. Thickness is 2mm. The exposed region is 10mm diameter and the angles were adapted to fit the interface between bumper sections. Of course you will not notice the 0.1mm 3D printer resolution fine lines in the final injected EPLD product, which will have a smooth surface.

As expected the results are very good. Comments and suggestions are welcome. If this design is approved I will proceed to final fabrication in EPLD material during next week.
 

Attachments

#53 ·
Hi Edgar,

I like the new design and think it is a good start but the exposed portion appears much too thick, or tall. The original exposed part of the gasket has a 10mm flat 'D' profile as shown in the following photograph. The new design appears to have a 10 mm diameter radius, which may not allow the bumper to fit into the recessed area in the upper rear of the car.

Automotive exterior Bumper Vehicle door Vehicle Car


Mark
 
#54 ·
The new design appears to have a 10 mm diameter radius

View attachment 1524976

Mark
Thank you Mark for the feedback. Understood and agree, except the "10mm diameter radius". The 10mm is diameter not radius. The "D" must be a "Flat D". Walkie talkie! Will reduce the "D" section shape to about 6 to 8mm turning it flat.
 
#55 ·
Hi Edgar,

You are right about the diameter being 10 mm and too large. Here is a picture of one of my old gaskets. The width of the "D" section as measured was 10 mm. The height of the D is only about 4 mm at the peak. Thanks for your effort and understanding to get this right.


Mark
 
#56 ·
Hi Edgar,

You are right about the diameter being 10 mm and too large. Here is a picture of one of my old gaskets. The width of the "D" section as measured was 10 mm. The height of this 'D' is only about 4 mm at the peak. Thanks for your effort and understanding to get this right.



Yellow Paper Measuring instrument Paper product


Mark
 
#61 ·
Hi Danny, the upper corner spacer has a negative angle to best match the two sections which adds an extra complexity in the steel tool. I expect to get the parts in two weeks maximum. So far, despite the complexity, tool cost is under control. Final price for the complete set of 4 spacers is still US$30.
 
#67 ·
Welcome Hans!

I hope your Montreal restoration is going well. Some photographs would be nice, if you can post them. I hope you have a copy of 'Alfa Romeo Montreal ~the Essential Companion' by Bruce Taylor.
It is an excellent reference source for anyone with a Montreal.

Mark
 
Top