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Author Topic: Checker Oval  (Read 423 times)

FlashGP

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Checker Oval
« on: September 14, 2017, 08:10:38 AM »
I am proof cutting the Checker Oval on page  43 of the Gemboree 2018 comp schedule and am having trouble with the meets on Row H.

Has anyone else tried to proof cut this design and had the same trouble?

Regards
Flash
Yours Sincerely
Flash (Gordon)

Rej

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Re: Checker Oval
« Reply #1 on: September 14, 2017, 09:58:38 AM »
Hi Gordon, I just tried to proof cut it in my app and sure enough, something goes wrong when you get to tier H. Now if you zoom right in on the diagram in the PDF (link in case anyone wants to follow along, P.43), you'll see their meets also don't line up, bit of a shame...

Now this can be corrected to perfect meets by cutting tier C at 28.28 instead of 28.35 and tier D to 31.46 instead of 31.63 but I guess the question is: do you follow the rules to the letter and end up with bad meets or correct the angles for tight meets. Seems like a bit of a stuff up on their end if you're going to be judged on meet accuracy.  ::) Maybe you can count the meets in the diagram vs how many are listed in the instructions(53) to see if they did it intentionally, maybe as a test to see who's paying attention! (like my teachers used to say when called out on mistakes)


Rusted

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Re: Checker Oval
« Reply #2 on: September 14, 2017, 12:19:47 PM »
I hate that.
When I used to pick the designs for club comps I always had to proof cut them.
That was after the first year when I was the worst person in the world for choosing a design that just would not work.
It's surprising the amount of old designs that can't actually be cut without playing around with angles.
If you want an exercise in frustration have a go at some of the designs in early Lapidary magazines.

FlashGP

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Re: Checker Oval
« Reply #3 on: September 14, 2017, 02:02:39 PM »
Yes.  I thought the Comp Committee had to proof cut before setting the schedule.

This design is so bad it won't look like the diagram without changes to the angle of two tiers on the crown.  I am statting to think I made  mistake, but all the angles and indicies are as per the cutting instructions.

Having said that it has a great pavillion.  You cut the PCP first so rough loss is minimised.  Swap rows 2 and 3 and each row is cut to a meetpoint.  I will use to with my own crown next time Mrs Flash wants me to cut an oval.

They also seem to use 64 index wheels in SA.  Two of the Novice designs are 64 index and one of them requires fractional indicies when converted to 96 index.

It's ok for open comp,  but may discourage Novices.

Regards
Flash
Yours Sincerely
Flash (Gordon)

Rej

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Re: Checker Oval
« Reply #4 on: September 14, 2017, 02:10:07 PM »
This design is so bad it won't look like the diagram without changes to the angle of two tiers on the crown.

I wouldn't say that.

In my cut, it looks exactly like the diagram, i.e: with a missed meet where G touches (or doesn't quite touch) H.

I can send you my gemcad file if you want to compare.

FlashGP

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Re: Checker Oval
« Reply #5 on: September 14, 2017, 05:49:07 PM »
Hi Rej

Yes please,  it might help me work out what I have done wrong.

When i initially cut the pavillion it was bigger at the sides than the available area so I shrunk it 10% which made the 20 and 28 facets meet.  But that shouldn't have caused it.

The only other thing I can think of is that I have used a wrong meet point.  But they are all pretty simple except for the 2nd last row.

Regards
Flash
Yours Sincerely
Flash (Gordon)

Rej

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Re: Checker Oval
« Reply #6 on: September 14, 2017, 06:11:20 PM »
Yeah, it took me 2 tries to get the first few pavilion meets right myself. And I also ended up running out of rough when cutting P7 but luckily my app lets you "re-grow" the rough  :P

Here's my version. Just use the "no thanks, continue to view" link at the bottom if you don't have a Dropbox account.

https://www.dropbox.com/s/33dfwi9oicb9gag/Gemboree18%20Checker%20Oval.gem?dl=0

« Last Edit: September 14, 2017, 06:53:07 PM by Rej »

FlashGP

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Re: Checker Oval
« Reply #7 on: September 14, 2017, 10:19:39 PM »
Hi Rej,

You got the same result I did on my 2nd attempt.  Several meets are out and will need adjustment and the lines are not straight.  It's really obvious when you zoom in to the top view.

I ended up using meetpoints that caused the Centre lines to run straight and then adjusted the angles of rows B and D to bring in the meets.  Row D needed adjusting by 1.3 degrees.

Here's a link to the copy I adjusted.  https://www.dropbox.com/s/2w7n32hveuvmd3u/Checker%20Oval%20-%20GP%20Corrections.gem?dl=0

Swap rows 2 and 3 so that the girdle meets on the 1,1 boundary taking the guess work out of locating that meet.

Regards
Gordon
Yours Sincerely
Flash (Gordon)

Rej

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Re: Checker Oval
« Reply #8 on: September 14, 2017, 10:56:36 PM »
Well, yeah I know they're out, I'm just saying it does looks like in their diagram though, so the instructions can be followed to get what's shown.
If you make the angle adjustments I listed in my first post, you get something like this where all the meets hit.

https://www.dropbox.com/s/gg23ikmz3729kg4/Gemboree18%20Checker%20Oval%20%28corrected%20Rej%29.gem?dl=0

The centre lines will always be ever so slightly off but remember that's an othographic view, something that's not possible apart from being in outer space looking down on the stone with a super-mega zoom lens. No judge can measure that to say it's off by that small an amount.

Your corrections seem to have thrown off one of the girdle meets where the crown no longer lines up with the pavilion...  :o

Anyway, I'd contact them about it, or pick another design to compete.

I'm curious, are you going down to SA or would you be mailing in your entry?

FlashGP

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Re: Checker Oval
« Reply #9 on: September 15, 2017, 07:49:40 AM »
Hi Rej

If I enter it I'll be doing it by post.

Regards
Flash
Yours Sincerely
Flash (Gordon)

FlashGP

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Re: Checker Oval
« Reply #10 on: September 15, 2017, 10:52:54 PM »
Hi Rej,

Thanks for pointing out the problem with my girdle in the earlier try.  I have re-cut to correct them and updated the Gemcad file on the Drop box.

In relation to following the diagram to the letter of the diagram, it can never be because as soon as you use the angle adjuster to push the meets into place, the angles change if you keep the facet flat.

Regards
Gordon
Yours Sincerely
Flash (Gordon)

FlashGP

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Re: Checker Oval
« Reply #11 on: September 15, 2017, 11:57:32 PM »
I think it is a bit rough giving Novices and Juniors who are probably more likely to have a 96 index machine, a 64 Index design to cut without converting it.  Perhaps we can provide both the original design and a 96 index equivalent.

Here is the Gemboree 2018 Petunia design (for juniors) converted to 96  index.  https://www.dropbox.com/s/vbaup4o5sottvob/Petunia.gem?dl=0

Here is the JB Cross (for Novices) converted to 96 index.  unfortunately 1 pavilion and 1 crown row have 1/2 indexes. https://www.dropbox.com/s/w4ocpk0iz6ogj2o/JB%20Cross.gem?dl=0

Here is the Centeyre Brilliant as a 96 index design, it converted OK.  https://www.dropbox.com/s/5u9sxrk5pdvv3tn/Centeyre%20Brilliant.gem?dl=0

Yours sincerely
Flash

« Last Edit: September 15, 2017, 11:59:06 PM by FlashGP »
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: Checker Oval
« Reply #12 on: September 16, 2017, 08:06:37 AM »
That Centeyre Brilliant are they wanting people to cut that for comps?
We are a family of 4 from Southern Tasmania.

scratchie

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Re: Checker Oval
« Reply #13 on: September 16, 2017, 12:03:25 PM »
Re the JB CROSS pattern for novices .
That's ridiculous expecting novices to all have a 64 index wheel , particularly as some of the indexes don't transpose to a whole number on a 96 index.
John

MakkyBrown

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Re: Checker Oval
« Reply #14 on: September 16, 2017, 12:27:17 PM »
Re the JB CROSS pattern for novices .
That's ridiculous expecting novices to all have a 64 index wheel , particularly as some of the indexes don't transpose to a whole number on a 96 index.
John
Are you the designer John? 
« Last Edit: September 16, 2017, 03:08:39 PM by MakkyBrown »
We are a family of 4 from Southern Tasmania.

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