134 replies to this topic

[69k1100]

Oh and a good radius is great for airflow but an ellipse will give you that bit more.

[Mini Manannán]

Oh and a good radius is great for airflow but an ellipse will give you that bit more.

 

I know it maybe isn't the absolute ultimate shape but it if you have other ideas give us some clues, "an ellipse will give you that bit more" isn't a great help.

"

[69k1100]

http://www.profblair...lmouth_Sept.pdf

Or instead of getting narky you could use your common sense to do some entry level research. Here you go, all warmed up and ready to be spoon fed.

[Mini Manannán]

Who's getting narky?  

 

I printed off Professor Blair's thesis on two-stroke design (here: http://www.dragonfly...trokeDesign.pdf  ***Mahoosif PDF - 400 pages IIRC***)   As I understand it David Vizard's bellmouth was an extension of his work, my 'design' is an extension of Vizard's.

[GraemeC]

Could you design a way to slot the mounting holes so it could be slid under bolt heads and then nip them down to secure?

[Alex_B]

Yeah that would be easy enough, but there would still need to be a modification as you cant get a tool in there to nip anything up as it stands 

[Mini Manannán]

Could you design a way to slot the mounting holes so it could be slid under bolt heads and then nip them down to secure?

 

My first try was like that Graham:

 

 

It still has legs, we were going to slim a 1/2' spanner down for the job.  Depending the new slim-bell works I might (have to) try that again.

[Mini Manannán]

Yeah that would be easy enough, but there would still need to be a modification as you cant get a tool in there to nip anything up as it stands 

 

Have you offered it up for fit to your 44 yet Alex?

[Alex_B]

 

Yeah that would be easy enough, but there would still need to be a modification as you cant get a tool in there to nip anything up as it stands 

 

Have you offered it up for fit to your 44 yet Alex?

 

Aha nope! been at uni all day today and had a presentation to finish for today, I will see if I can do it tonight when I get home or tomorrow as I am only at home tomorrow finishing an aerodynamics assignment 

[vx220]

Not sure if this is helpful, but you can get thin spanners from bike shops (and occasionally FOC with a washing machine!)

Usually 3-4mm thick?

[Mini Manannán]

 

That version looks like there will be the same fitting issues, if it was me I would be making the trumpet longer to allow a spanner behind. Also watch out for clearance on the inner holes, on the one I printed there isn't any as the body of the bell intersected the hole due to the thickness mostly but a narrower throat would be an idea.

 

You run into clearance issues with the airbox, that's why I kept it so marginal.  The newer design goes very thin at the edge, hopefully it'll deform enough to get fingers underneath.

 

 

The thing is, you lose when you go longer, according to the yellow bible anyhoos.  I've already done a longer, wider-throated trumpet for mounting on the outside of my virtual airbox, here it is:

 

 

It could be resized, redrawn, whatever.

 

 

This the latest Carb bellmouth, lots of midnight oil burnt last night, still not solid for printing though 

 

[Dusky]

 

 

That version looks like there will be the same fitting issues, if it was me I would be making the trumpet longer to allow a spanner behind. Also watch out for clearance on the inner holes, on the one I printed there isn't any as the body of the bell intersected the hole due to the thickness mostly but a narrower throat would be an idea.

 

You run into clearance issues with the airbox, that's why I kept it so marginal.  The newer design goes very thin at the edge, hopefully it'll deform enough to get fingers underneath.

 

 

The thing is, you lose when you go longer, according to the yellow bible anyhoos.  I've already done a longer, wider-throated trumpet for mounting on the outside of my virtual airbox, here it is:

 

 

 

It could be resized, redrawn, whatever.

 

 

This the latest Carb bellmouth, lots of midnight oil burnt last night, still not solid for printing though 

 

 

 

Is there any printable material that could withstand like 10 nm torque?

Captive nuts or similar might be an option too, I don't think these things should be torqued very hard..?

A kind of printed stud could work too if it owuld be printable?

Edited by Dusky, 05 January 2015 - 06:52 PM.

[Mini Manannán]

The new version is done.  I scaled a circle into an ellipse, cut holes and slots out then extruded the whole lot by 2mm. Then I extruded the centre wall by and then drew the profile of the bellmouth:

 

 

A prod of the Follow Me tool and 5 seconds later I had it:

 

 

 

Solid for printing first time

[Mini Manannán]

I looked at a Gilera Runner engine tonight and had a brain wave   

 

 

I've called them radial slots.  Easiest mounting yet

[Alex_B]

Updates!

Finally had some time to play with the print. 


 

It fits!