Engine casings

[keuk]

Hello,

 

Do anyone knows how Quattrini, Falc and SIP proceded to make their engine casings ? Did they use a 3D scan of an original casing and then make changes on a 3D model or did they recreate a full new and editable 3D model ? Maybe each one add a different technic ? It would interest me a lot to understand the process.

 

I don't know if the 3D scan technology is able to recreate plane surface, cylindric shape with axis (for the correct position of each elements of the bearings ...) that you can use after in a 3D software like solidworks to make sketches and new geometries.

 

I found this picture of the SIP model on google, the model is so close to the geometry of an original one that I have doubts and I would like to understand.

 

Bearbeitet 16. Mai 2013 von keuk

[FalkR]

If you scan the engine casings by computed tomography you'll get a data output type STL.

These files consits of many litte plane triangles (connecting 3 points) which mold the entire structure.

 

But there are quite a few people/companies who have the proper tool to work on STL files (very expensive programs)

Normally these files are "closed" and you aren't able to change anything. If you like to, you have to convert it into general CAD files ".step, .vda" e.g.

I stopped my quest to find any freeware or payable software to convert it.

So you have to bite the bullet and mold your version on your own.

 

I think SIP & Co. scanned some engine casing surely, but to design new parts or geometries in this complex structure it is beneficial to have a CAD part.

There some guys with many crazy skills to exactly replicate such plane structures in CAD. Often designers for textile and surfaces who create complicated structures like shapes of new car models.

 

Concering to the italian faction who cast new casings, the build some negatives with sand mould from available engines.

After that they changed a few things before casting. A pragmatic approach, but you won't spend to much time in designing CAD modells.

 

So far...

Bearbeitet 17. Mai 2013 von FalkR

[keuk]

Ok, thanks. So once you have the STL file, there are softwares able to recreate basics geometries, like plan, radius, // between axis, screw hole etc.. right ?

[FalkR]

I phoned a lot, but afaik there are explicit programs to recreate the geometries ( keyword : surface reconstruction, surface feeback program )

I'm going to search for the names of the programs. Anywhere i wrote the names down.

If you are interested.

Bearbeitet 17. Mai 2013 von FalkR

[BerntStein]

Hi there,

 

what is the purpose of the created 3D-model?

CNC-milling? exact copy? perfect casting model? 3D funmodel-look-alike, no hardware to be built?

 

I´d say a scan would help a lot creating a new casing. This new casing would be modeled right over the scanmodel.

Meaning: not modifying the scan, just use as a blueprint.

Things to know would be some absolutely exact measurements of the bearing-positions.

 

I am doing modeling on complicated pieces in catia. compares little bit to re-modeling such a "potatoe". can be a lack of fun sometimes.

 

i can tell you: i would not modify the scan!  generate an assembly in CAD and put the scan and your model exactly into it. depending on how precise you want to generate all the small corners and how godd you are: 40+++ hours (simplyfied CNC-copy, function 1:1 eventually in one week, not counting search for infos)

 

maybe someone with perfect software and lots of practise would take the other way in modeling.

Using the points of the model directly.

 

best regards

 

Bernt

[keuk]

Well at the beginning I intended to built a identical model with all casting constrains and when I saw the complexity to transpose a real model on 3D with accuraty I was beginning to wonder , dammed how did they do to have such a good result so close from the original with the same details that are proper to the old manufacturing process when 3d didn't exist.

But it appears difficult to have the answer, even if the 3d scan as a blueprint appears interesting.

Nevermind I kept going with my caliper... So the model is very close from the original base with some optimisations. But a 3d scan would have been perfect to validates the bearing positions for exemple.

Bearbeitet 19. Mai 2013 von keuk

[keuk]

Another model with a read intake and a VHSB found on internet.

 

 

Bearbeitet 26. Mai 2013 von keuk

[BerntStein]

sometimes it helps to print a section on a plotter dimensionally 1:1

then cut it and put it onto the original casing

never forget to control the plot on the paper. real plotters should be in+-o,2mm on 500mm

 

this method helped me with the rims and some other parts.

[Tim Ey]

Bearing position - check this out

www.germanscooterforum.de/topic/204191-smallframe-motor/

[keuk]

Many thanks, I knew I had seen it somewhere !.

[gommon]

I have try too.. in Catia V5.. But the cases are amazing to design.

[gommon]

see some of my parts...

[keuk]

Nice job, is that you ?

 

http://grabcad.com/library/stock-vespa-flywheel-mod-with-polini-evo-ignition-fan

[keuk]

I kept going on the casings but I have a problem with the carburator that touches the shock and the casing?

 

If I want to keep a standard shock I have to turn the carburator and it touches the flywheel area, and it will dicrease a lot the airflow if I increase the bump on the casing... I need to find something else... I was hesitating on inclining the cylinder more (like a px) to gain room ?

Bearbeitet 27. Mai 2013 von keuk

[Tim Ey]

At first: 

Use a Keihin

I would prefer to have a small buckle in the flywheelarea than to have an other cylinder-angle.

 

Are you painting this for fun or are you going to produce (and sell) it? When you are going to produce it, I have some design-Ideas: 

- Use bigger crankshaft bearings

- Use a crankshaft that is wider - for example a "Kingwelle" for the Quattrini-carter.

- Than you can use a Honda CR / NSR (Falc) or a Rotax Reedvalve instead of the RD350 Reed

- Make the sealing surface around the cylinder as huge as possible, so that for example Motocross cylinder can be mounted with ease.

[John F.]

At first: 

Use a Keihin

I would prefer to have a small buckle in the flywheelarea than to have an other cylinder-angle.

 

Are you painting this for fun or are you going to produce (and sell) it? When you are going to produce it, I have some design-Ideas: 

- Use bigger crankshaft bearings

- Use a crankshaft that is wider - for example a "Kingwelle" for the Quattrini-carter.

- Than you can use a Honda CR / NSR (Falc) or a Rotax Reedvalve instead of the RD350 Reed

- Make the sealing surface around the cylinder as huge as possible, so that for example Motocross cylinder can be mounted with ease.

Nothing wrong with Dell'Orto.( Keihin is for them who don't know how to set up a carb )

 

"Youre design ideas" already have a solution. It's called:  'Quattrinni carter'.

 

But a bigger bearing and more surface for the cilinder base is always helpfull.

Bearbeitet 28. Mai 2013 von John F.

[keuk]

It's just for fun, a kind of cad training. It would be a too big investment, not very interesting with all the solution already available for this niche market. Plus it would be a bit prententious with my small engine background.

 

For the reed this one is already too big, it's wouldn't help solving my problem. For the other suggestion, yes maybe later.

[Tim Ey]

"Youre design ideas" already have a solution. It's called:  'Quattrinni carter'.

You don´t say!

[gommon]

Nice job, is that you ?

 

http://grabcad.com/library/stock-vespa-flywheel-mod-with-polini-evo-ignition-fan

Yes, I have this parts too. ;)

[gommon]