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  #11  
Old 06-15-2020, 06:23 PM
Kerry Pinkerton's Avatar
Kerry Pinkerton Kerry Pinkerton is offline
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Did the Kurtis roadsters have door returns? I have no idea but don't know why they would do the work or the weight on a race car. Even as minuscule as the additional metal would weigh they saved every ounce they could.
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  #12  
Old 06-15-2020, 07:26 PM
Sean in CT Sean in CT is offline
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Kerry - my car is supposed to look like a rally car patterned after the 1953 Kurtis 500B indy car. They had 1 seat and no doors. Kurtis also made the 500S, which was their 2 seat street car - looked kinda like an Allard. It had a similar silhouette as the race car (sort of, if you squint.)



Kent - thanks for the wonderful compliment. It is supposed to look like it was built in 1955 for the 1956 Carrera Panamericana race. I am going to drive it to work when i am done.

Seems that Kurtis' achievements are being lost to history, even to car guys. I wanted a cool, unique, American sports car that paid tribute to history, so this is what i came up with
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  #13  
Old 06-15-2020, 09:35 PM
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Not quite the offset I think you'll need, but here's one I did recently...


Quote:
I received a state of the art drawing the other day, and was asked if we could duplicate the 1/16 offset shown...





Of course this meant we needed some new tooling..











Our first sample, with the proper 3/4 flange...











We had another panel that would require the offset on two adjacent edges, so one more sample...











video action:


https://www.youtube.com/watch?v=oxhk_O1FJTM

Sometimes we make tooling and are pleasantly surprised at what it will produce. Blind squirrel finds a nut..
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Last edited by MP&C; 06-15-2020 at 09:40 PM.
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  #14  
Old 07-19-2020, 02:28 PM
Sean in CT Sean in CT is offline
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So, I finally joggled my cowl for the door opening. Did it by hand, annealed a few times, kept checking the shape with a radius gauge and got it really close. Once the panel is fully attached ill fine tune it. All the advise was so helpful


I built a louver press since I last posted. I used the mittler brothers 3" die and built a 42" frame. Still needs some finish welding on the gussets and a coat of paint. I made a simple lever as shown by Joe Hartson a while back. Works great on 0.063 aluminum. The linkage took a few tries to get perfect. It has to cut just before going over center. Should be easy, but the flex in the frame means it requires a little trial and error. 0.100" is the difference between working great and not.

Louver press 7 19 2020.jpg

Kurtis door joggle 7 19 2020.jpg
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  #15  
Old 07-19-2020, 05:10 PM
crystallographic crystallographic is offline
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Quote:
Originally Posted by Sean in CT View Post
So, I finally joggled my cowl for the door opening. Did it by hand, annealed a few times, kept checking the shape with a radius gauge and got it really close. Once the panel is fully attached ill fine tune it. All the advise was so helpful

I built a louver press since I last posted....snip...
Should be easy, but the flex in the frame means it requires a little trial and error. 0.100" is the difference between working great and not.

Nice joggle, Sean.


Re: pressure machines needing .001" tolerance.
Any tiny amount of frame flex diminishes pressure, thereby adding to the needed force/ram distance.

i.e. "Chasing the flex."

The builder chases his tail for a while when learning this bit of machine design - adding gussets, side plates (fish plates) etc.

Success makes for joy, in the end.

(or relief... )
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  #16  
Old 07-19-2020, 07:45 PM
Sean in CT Sean in CT is offline
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Thanks Kent! the machine flexes about .150 when punching the louver. I was able to maintain 0.005 die clearance which seemed to be the "sweet spot" Before adding the side gussets, it flexed about .200 which really screwed up die alignment - had to use .008 clearance which increased the cutting force immensely. If i was doing steel, it would prob need further stiffening.
FWIW when i stand on the end of the press, it flexes 0.015" - 190 lbs....maybe a few more
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  #17  
Old 07-24-2020, 01:10 PM
crystallographic crystallographic is offline
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Originally Posted by Sean in CT View Post
Thanks Kent! the machine flexes about .150 when punching the louver. I was able to maintain 0.005 die clearance which seemed to be the "sweet spot" Before adding the side gussets, it flexed about .200 which really screwed up die alignment - had to use .008 clearance which increased the cutting force immensely. If i was doing steel, it would prob need further stiffening.
FWIW when i stand on the end of the press, it flexes 0.015" - 190 lbs....maybe a few more

Hi Sean,
I have a punch/die nibbler, 1957 Campbell. It will do 10 ga stainless all day long. Frame is 5inch flame cut steel plate. The frame has a web/backbone 24inch with a throat of 36inch. So that is a 2/3 ratio, of web/throat (gap does not matter). I have power shrinkers with various frames, fabbed, or cast steel, cast iron, all with ratios of 1/1 and very minor flexure. Side wall thickness and profile is important, but I watch the ratio, very much, constantly. My Whitney press is now converted to air-cyl as a louver punch. 1inch plate sides, 14.5inch web, 24inch throat : 1.66ratio. Will punch 4.5inch louver in 20ga steel, after a 3 second pause for cyl/frame to load up .... POW!

I see machines made in small shops that flex .200 with 250 lb loads, too often. .... And then I see a serious (15foot tall, 6 foot bed) 500T H press made in a small shop out in the boonies ... serious working machine with work coming to it from 200 miles.
Might as well build it stout, as long as you are at it.

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Last edited by crystallographic; 07-24-2020 at 01:56 PM.
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