Gilera Bi4 Nordwest 3d scanning/modelling

[marco70]

always more beautiful good !!

[Duranti]

marco70, I am glad you are enjoying the parts, thank you for your support and for following this project! 

Today I finished scanning the right hand side carburetor, and I have included a picture of the scan inside the scanning program, the results are pretty good! Tomorrow I will scan the left hand side carburetor, after that I will import these parts into Fusion 360 and start the modelling process, should be fun, and I will post update as soon as I have something of interest to show you guys! 

[Matte]

Concerning the assembly shaft/sprocket, you could use this solution, even if it's not correct. What do you think about it?

[Duranti]

Hello Matte!
Yes, I think it would be possible to use a straight sided spline, I would have to do some test-prints to see if I am able to achieve the desired resolution, as well as figure out the best tolerance, which is quite tricky with a combination of small dimensions like this (approx. 8.5 mm diameter) and 3d printing, but I will give it a try. 

It is also worth considering that the final drive shaft is hidden from view thanks to the large washer holding the pinion in place, so it will not be visible to the eye once it has been assembled, and due to the scale (and plastic material) a simplified alternative to spline (aka hexagonal) might be a more durable solution, I will do some tests and we will see. 

[Duranti]

Hello friends,
First of all; WOW, this thread now has over 3000 views, thank you all for your interest in this project, and for following this rather lengthy build!!! 

Hopefully I will be able to finish the 1:3 scale engine before the end of November, if I am able to find the remaining parts, but hopefully it will be worth the wait!!! 

I finally got the carburetors scanned, it was a difficult task because of all the geometry and areas that were out of range from normal scanning angles, but I have enough information now to start modelling the carburetors! Also the scanned carburetors will aid in designing the new NW replacement manifold I am working on, which is starting to take shape! 

[Matte]

Good work, as always

[Duranti]

Thank you Matte, I appreciate it! 

Have a great weekend Gilera friends!

[vninja]

Tks Tiranti, too you!

[bigbore]

ok Trond, this is your final test! 3DPrinting those carbs will be a rather complex task IMHO.
I think it's mandatory printing a single carb at a time and... maybe splitting in half (vertical plane) then glue togheter those two halves?

[Duranti]

bigbore,
You are completely correct; printing the carbs might be the most difficult part of this entire build!
This also applies to the modelling process, since there are very few flat/straight faces due to the die casting process of the carbs, and there is alot of geometry that needs to be accurately captured in the 3d model.

Also, you and me think very much the same with regards to printing the carbs, I will print the carbs individually, and due to the nature of a single head FDM 3d printer (any overhanging angle below 45 degrees will be of lower quality surface) there will be compromises, so you are correct about maybe having to split the individual carbs into two pieces during printing, and combining them afterwards using either glue, internal clips, hidden screws, interlocking geometry, or a similar solution. This way we can achieve the highest fidelity compared to the original 1:1 geometry. 

I am also considering making a negative silicone mould to cast the carbs, individually, in one piece, I will explore this option as soon as I have completed the carbs in a conventional 3d printed format.

Either way, if I am able to achieve an acceptable quality final result for the carbs, I will be happy, because it will indeed be a difficult task! 

[Matte]

If you decide to cast the carbs, I suppose you will go to use a bicomponent epoxy resin......

[Duranti]

Good evening Matte,
Regarding casting of the carbs; I have not investigated enough yet to decide which material to go for, but I have seen alot of excellent results using polyurethane, perhaps something like this would be a starting point for finding the best material for this application:
https://www.freemansupply.com/products/liquid-tooling-materials/fast-cast-polyurethanes/repro-fast-cast-urethanes

First though I will give my 3d printer a chance, with the correct settings I should be able to get good results, time will show! 

[Matte]

Hi Trond, I confirm you that polyurethane should be a good alternative to the resin. Let's wait and see what your 3Dprinter will do.

[Duranti]

Matte, thank you for the confirmation, I have very little experience with casting resins, and good advice is always appreciated! 

Here is another link to a company called Smooth-On, which seems to be one of the big players in the casting resin industry, they seem to have just the right products for the Bi4 application:
http://www.smooth-on.com/product-line/smooth-cast/

Back to modelling the carbs now, they are very intricate aluminium castings with lots of features, and the non-proportional shrinkage (very difficult to get proportional shrinkage due to different cross-sections) during solidification which leads to slight ovality in the circular areas. So it's all about figuring out the design-intent during replication/reverse engineering, a challenging task, but great fun! 

[Gatto Silvestro53]

No news?
Maurizio