Sand casting unobtainium parts at home.

Most of the hot rod ones are copies of the of the original Ford ones. I would say they would be closer to 6" wide at the fan part.
The Robri one you posted looks like it is close to 3x the width of the part that fits the tailpipe.
So I would say multiply whatever maximum size tailpipe they say it fits by 3 to get your overall width.
Bit different in appearance, but from a cost perspective these skull cast alloy tips are around $150 AUD each including postage off Amazon.
So a comparable cost to the Robri ones.🤷‍♂️

images (6).jpeg
 
Thank you GP. I'll have to fly by the seat of my pants and freehand a sample pattern until I have pleasing proportions. My pipe size is 50mm but I don't want to end up with 150mm overall. I'll have a lash today and see what I can come up with.
 
Thanks but I'll be right, I'll freehand a pattern. I'd assume your sample would be for a smaller pipe size anyway..? I'll just upscale until I have pleasing proportions, after all this is just a bit of minor bling.
 
56 Fregate said:
Thanks but I'll be right, I'll freehand a pattern. I'd assume your sample would be for a smaller pipe size anyway..? I'll just upscale until I have pleasing proportions, after all this is just a bit of minor bling.
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Yes, smaller indeed: 4CV pipe size. About 1" in Christian units.
 
Hmm, at first glance it looks like it will indeed end up being 150mm wide for a 50mm pipe size. I don't wan't it to be too ostentatious but I'll persist with developing the shape as the day progresses.

IMG_6431[1].jpg
 
56 Fregate said:
Hmm, at first glance it looks like it will indeed end up being 150mm wide for a 50mm pipe size. I don't wan't it to be too ostentatious but I'll persist with developing the shape as the day progresses.

View attachment 222501
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Once you taper it all down the width will look OK.
Anything much smaller is going to look too narrow gutted on a 2" pipe.
If anything needs a bit of bling it's a Prius.
 
It has some merit I suppose. My foam block is degrading rapidly from the solvent based glue
I used so I'll switch over to a block of softwood in due course but not today.

IMG_6433.JPG
IMG_6432.JPG
 
Here you go. A genuine Robri #314. Pipe diameter 30 mm. Lovely thing. The underside is flat/planar and there isn't a "saddle" area on top. Let me know if you want any other angles.

Robri 4CV tailpipe 30 mm pipe diameter 2.jpg
Robri 4CV tailpipe 30 mm pipe diameter.jpg
Robri 4CV tailpipe exterior 2.jpg
Robri 4CV tailpipe exterior.jpg
Robri 4CV tailpipe interior.jpg
 
Ahr lovely, that gives me all the detail I need. My version will naturally be fatter in the neck to suit a 50mm pipe.
 
56 Fregate said:
Ahr lovely, that gives me all the detail I need. My version will naturally be fatter in the neck to suit a 50mm pipe.
Click to expand...
It doesn't have to be MUCH fatter, does it! It's quite elegant I reckon, and quite simple.
 
With the wizardry of the digital age I deduce that these are the required dimensions..give or take. I'll work my version along these lines. JW can I have an overall height/thickness from the flat underside to the highest point?

Untitleda.png
 
56 Fregate said:
With the wizardry of the digital age I deduce that these are the required dimensions..give or take. I'll work my version along these lines. JW can I have an overall height/thickness from the flat underside to the highest point?

View attachment 222528
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It's more cunning than I realised. At the ROBRI badge, 34 mm. At the pipe clamp area, definitely 29 mm, so it rises relative to the flat base along its axis, more or less linearly, then drops away a few mm past the ROBRI badge as the fin rises relative to the base. The fin has a maximum height of about 5 mm. So it bells out more than is immediately apparent. I'll send another photo. Back to the workshop!
 
OK more subtly. There is a beak! The first photo shows the flattest part of the basal plane in the vice, with a gradual curve from there to the end of the fitting. You can see that the "beak" has some tapering across the fitting too, in the second photo. So about half of that lower edge is planar and then it curves one way for the subtle beak and quite a bit for the top that fits over a wee bit less than half of the pipe outside diameter.

It's one very 3-D item.

Robri 4CV tailpipe profile.jpg


Robri 4CV tailpipe profile 2.jpg
 
Okay thank you Sir, now it's clearer. My foam block from this morning has stabilised from the solvents and is still usable. I'll fatten it up where needed with body filler and develope the shape more closely on the morrow.(y)
 
Is that a +/- 3mm wall thickness?
JW - are you able to get a side-on photo of that laying on a flat surface to indicate the curve of the basal plane?
This is fascinating. I’m going to fire up some popcorn. 😉
 
Will do when it is light! Yes, around about 3 mm - quite light, isn't it! I was trying to achieve that for you but it's not that clear in the photos. I'll pull out the studs so that I can put it down properly and photograph it from a couple of directions. There are more subtle curves than I at first realised.
 
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