CB750 Engine - 1/4 scale

[Brookesy]

So I've finished my first engine and designed the second - see pic. So far I've 3D printed the parts and made minor changes to the prototype. Hopefully start cutting metal soon. In the meantime the brain is working overtime...

I own a 1971 Honda CB750 - finished rebuilding about 5 years ago.
Brain thinks: What about a 1/4 scale replica engine? The whole bike?

While I was restoring the bike I drew most parts in CAD but only in 2D and never quite got finished. Raised eyebrows in the house when I started putting wheels, engine parts etc. on the kitchen table to take measurements

The budget does allow for a 3D scanner at present so it's going to be a long process but the plan is to continue the project in 3D.
Has anyone got access to a 3D scanner and a CB750 engine? not likely...

Anyway, I just I'd share my thoughts

 

[pjpickard]

Here are a few files:

https://grabcad.com/library?page=1&time=all_time&sort=recent&query=CB750

 

[napoleonb]

I saw your post on the CYB Facebook group as well but you stated there it is going to be a full 1/4th scale CR750 model with working engine.

How faithfully are you intending to copy the internals / externals of the engine and entire bike? Are you contemplating on making your own oil pump / transmission gears and carbs for that matter?

3D scanning is quite fun as is old fashioned 3D modelling by measuring the parts but when making a (scale) engine it comes down to the machinability and production methods on hand. Cutting corners makes for better machinability with lesser equipment or knowledge, no disrespect ment, and probably less machining time as well.
Also keep in mind that scaling length by 1/4 means scaling area by (1/4)^2 and volume by (1/4)^3 so to make a nice running engine you have to cut some corners or rely on proven designs if you're not willing to do all the calculations.

 

[napoleonb]

Most of the models from the link to Grabcad are mine.
So I do own a lot of original CR750 parts (which cost a small fortune) and modeled them in 3D (lots of time involved).
Most of the standard CB750 parts which I replaced by CR750 parts or standard parts checked to re-use in my bike are modeled in 3D as well, so I have quite the database.

But I am a bit hesitant to just "give" or let others use my models, but I'm sure you can understand my point of view.
Didn't want to burn you in the previous post but if this is something you are really considering to do and if you're willing to invest and help the community in some sort of way I might be willing to help some.