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  #11  
Old 03-10-2019, 06:48 AM
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neilb neilb is offline
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i think i have a little off cut in the garage so i may have a quick go lol
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  #12  
Old 03-10-2019, 07:52 AM
Jaroslav Jaroslav is offline
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I am interested in the comparison of times. I gave the question for my orientation in this problem.

How much time do you think you need for to make such a simple shape. You have to measure both radii. The result must be accurate. You make only one piece.

I just want to compare. Then I will write to you how much time I needed.
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  #13  
Old 03-10-2019, 03:48 PM
Jaroslav Jaroslav is offline
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Today I tried a little smaller again. Step by step photo. Total time 60 min. But no measurement, just a test. I already know the directions of shape. You need to train even silly things. I'm giving the procedure.

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  #14  
Old 03-11-2019, 01:18 AM
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well i got hold of a piece of scrap, measured up best i could, 500mm long, just under 200mm wide. i don't have much to gauge the radii but it took 20 minutes to go from flat to this shape, with a sand bag and a standard wheel

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i don't have much time to waste making scrap i don't need so once it was to this shape at 20 minutes, i reckon under an hour to finish the piece, starting off with a wider piece than needed would be better, that way any shrinking marks would be in the waste material being cut off.
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Old 03-11-2019, 02:15 AM
Jaroslav Jaroslav is offline
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Quote:
Originally Posted by neilb View Post
well i got hold of a piece of scrap, measured up best i could, 500mm long, just under 200mm wide. i don't have much to gauge the radii but it took 20 minutes to go from flat to this shape, with a sand bag and a standard wheel

Attachment 51716
Attachment 51715

i don't have much time to waste making scrap i don't need so once it was to this shape at 20 minutes, i reckon under an hour to finish the piece, starting off with a wider piece than needed would be better, that way any shrinking marks would be in the waste material being cut off.
Neil and all. Thank you for comparing your experience.
It looks silly, but we were the first fender did 10 hours !!!! Yes - incredible. Of course we talked about it, and so on. I did not understand where the bug was ... we measured and tuned exactly, but the time got me.
We just started wrong, it was hardened sheet metal, but the time .....

On my next test, it was confirmed. It should be the 3 hours and the lunch as planned. There was a lot of talks and little masters of shaping. Thank you for all posts.
Add your opinions. It's a simple shape, but it can employ you.
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  #16  
Old 03-11-2019, 07:02 AM
mark g mark g is offline
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Quote:
Originally Posted by Ken Hosford View Post
No dimensions stated . In mild steel to generate the fender shape well less than an hour on a Pullmax with doming dies starting with ~ 700 mm radius lower at least 2 thirds as wide as stock , dropping radius ~ 50-75mm increments as the part shapes up you need smaller increments 25 mm then 12.5mm then 6mm . Sounds like a lot of tooling , you can form metal over wood dies , I use MDF [ brownish fine particle board ] glued up and turned on a wood lathe set up with a crude x y slides made out of pipe and hand rail fittings .If you tie the cross slide to the head stock starting with your link parallel with the bed of the lathe and the tool bit dead on center ars you pull cross slide the link pulls the carriage toward the head stock forming the radius If epoxy coated these dies are pretty durable , I thin my epoxy with xylene maybe 10 % or less it makes it penetrate like crazy it takes a lot of coats to get it to gloss over .
you can also use particle board but it is hard to get a good surface and it takes a lot more epoxy.
By passing a narrow rectangular piece thru them it will form a part with the same radius along the length as across , not the shape you want so you pass it through an English wheel with 2 radiused upper wheels and a large wooden lower wheel with a radius ~30% smaller radius than the desired radius across final product . You need the smaller radius to allow for over bend necessary
I have formed 1 mm stainless , 1 mm titanium 1 mm hard brass on these dies .
To make the fender shape less bead if it is the size range I think it is possibly 4 in 1 hr . The process is very repeatable .
The real trick is to know when to stop doming die forming and start rearranging the shape on the English wheel
The trick to using wood die is moderate steps if you take to big a bite it will wad metal up requiring E wheel work to save it . Done properly the surface finish should be unharmed
By using large diameter and large radius dies you are not so much stretching as forming shallow waves that you are compressing much like tuck shrinking or thumb nail dies but the other end of the spectrum low angle low distress low stress , hence the ability to work the near impossible titanium I am using a P7 and 1.5 mm stainless is about as far as I have had the nerve to try on them and the machine
Ken,

Can you show a sketch of the cross slide set up you're describing for making the large diameter dies? I think I understand you description but not sure.
Thanks.
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  #17  
Old 03-11-2019, 06:47 PM
Ken Hosford Ken Hosford is offline
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first picture you see a Boise Crane wood lathe head stock mounted parallel with bed are 2 pipes [ x axis ] one on each side mounted above are 2 pipes at 90 Degrees these 2 pipes slide R & L on first pipes . the square wood top moves on the 90 degree pipes [ Y ] axis .
There is a link mounted to the aluminum extrusion with tee slots and to under side of top by changing length of link you change the radius . This arrangement work better for larger radii I use a pivoting conventional radius cutter for up to 4.25 " and it is a struggle for a few inches on the x y .
Would I build it this way again never it was made this way due to materials on hand MOH . The fit of pipe thru fittings is horrid one could make much better pcs out of wood . But it works . The base was screwed up out of 3/4" plywood I used 1/4 bolts as wood screws drilled a 3/16" tap hole 1/4" thru hole in pcs being mounted it takes a bit of force and generates a lot of heat and you want to use min of 3 - 4 time bolt diameter thread engagement .

xy wood lathe.jpg

xy lathe.jpg

Last edited by galooph; 03-12-2019 at 02:12 PM.
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