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#1 Something Stirs in the Workshop
Posted: Sun Oct 29, 2017 5:39 pm
by vinylnvalves
Thought I would plagiarise Mark's thread, as this is a long project ( hopefully not as long as Marks
)
I am building a new pair of midrange horns, but this time I have got for an elliptical one to get better vertical integration. I have had the definition of the horns for a number of years curtesy of JMLC who gave me a spreadsheet. After a few years of wondering how to make them, I decided to CNC them. So about 18 months ago I started building a CNC router, with a bed big enough to machine the 200hz horns. After commissioning the machine and learning how to write Gcode, I started the horns.....
Decided to machine them in slices and glue them together, using a watermark aproach machining in 1mm steps for the inner and 2mm steps for the outer. Here's some pictures of how far I have got .....
#2 Re: Something Stirs in the Workshop
Posted: Sun Oct 29, 2017 6:04 pm
by steve s
Very impressive Steve... building a cnc router too, wow !!
#3 Re: Something Stirs in the Workshop
Posted: Sun Oct 29, 2017 7:16 pm
by vinylnvalves
Thanks Steve, The aim is to have them finished for the next Owston meet. The next sections start to get big and have a re-enterant feature so there will be some hand shaping too as I only have 3 axis. Widest point is about 800mm, so reckon I will need a couple of sheets more of birch ply.
#4 Re: Something Stirs in the Workshop
Posted: Sun Oct 29, 2017 7:34 pm
by Dave the bass
Phwwwwwwwwworrrrrrraraaaaa(h)!
Bonkers and ace at the same time. Respect.
#5 Re: Something Stirs in the Workshop
Posted: Sun Oct 29, 2017 7:37 pm
by IslandPink
Nice one !
I wondered what you were up to.
Something good about the title too....
Reminds me I must talk to Chris V about how his mate down South is doing with some elliptical JMLC's , they are probably a bit smaller , maybe 350 or 400Hz.
#6 Re: Something Stirs in the Workshop
Posted: Sun Dec 10, 2017 5:41 pm
by vinylnvalves
Done a bit more machining and gluing. On the final leg now. Just got the ears to do. Had to get into more complex machining to get the re-entering features. Changed to a ball nose cutter which gives a better surface finish.
#7 Re: Something Stirs in the Workshop
Posted: Sun Dec 10, 2017 6:13 pm
by IslandPink
Now you've got me confused. What's with the ears ?
#8 Re: Something Stirs in the Workshop
Posted: Sun Dec 10, 2017 6:25 pm
by vinylnvalves
The bits that go on the top and bottom of the horn, another 250mm of material to add.
#9 Re: Something Stirs in the Workshop
Posted: Sun Dec 10, 2017 6:34 pm
by vinylnvalves
Something like this...
- 5536689A-C3C2-48A7-ACFB-6C12395CEC89.jpeg (27.78 KiB) Viewed 52425 times
#10 Re: Something Stirs in the Workshop
Posted: Sun Dec 10, 2017 6:41 pm
by IslandPink
Ah yes, of course. Makes more sense when the full top/bottom flanges are there.
What Hz is the little one ?
Wondering about trying the Radian 745Be on a small elliptical some time, around 700Hz to 1000Hz exp.
#11 Re: Something Stirs in the Workshop
Posted: Sat Jan 20, 2018 6:40 pm
by vinylnvalves
Finished matching and gluing all the sections together now. Next step involves a Japanese rasp... got to decide if I want wood finish of a lacquered finish, if later need to use glass fibre tissue and gel coat.
Was hoping to get a room at the Scalford show but out of luck
will have to audition them at Owston instead,
#12 Re: Something Stirs in the Workshop
Posted: Sat Jan 20, 2018 7:09 pm
by Dave the bass
Phwoaaaaaaaaaaaaaar (etc!).
#13 Re: Something Stirs in the Workshop
Posted: Sat Jan 20, 2018 7:17 pm
by Ray P
Outstanding work!
vinylnvalves wrote: ↑Sat Jan 20, 2018 6:40 pm
...if later need to use glass fibre tissue and gel coat.
If you're talking about polyester gel coat I wouldn't go there; it's quite viscous and it'll be really hard to get a smooth finish. Personally I would use some glass or carbon tissue wetted out with low viscosity epoxy, something like this;
https://www.bucks-composites.com/produc ... -cure-time
I've use it for finishing model boat hulls (and mould plugs) and if you remove all the excess resin you can get a paint like finish.
#14 Re: Something Stirs in the Workshop
Posted: Sat Jan 20, 2018 7:42 pm
by vinylnvalves
Thanks for the info on the finishing epoxy, yes this probably what I meant, coloured gel goats do allow you to sand and buff it to a mirror finish though, without needing to spray it. Have some bits of tissue and epoxy left over that I might practice with first.
#15 Re: Something Stirs in the Workshop
Posted: Sun Jan 21, 2018 2:44 pm
by Mike H
Good lord.