nose rib lightening holes

[fairchild]

I have been pressing my nose ribs against a rubber pad to press in the central holes and bend the outer edge over about 1/2 way or so.....
Then I roll the outer flange over more with a little dead blow hammer.... then I fluit..... then finish the bends to 90 degrees with that
hinged gizmo that the RV guys use..... Then a bit more fiddling and im done. The only "bug" is that my rubber is only forming the center
flange to about 20-25 degrees instead of specified 30.

I tried making a beveled plug to mechanically press them the rest of the way (in the hydraulic press) --- and it did--- but it also induced
some pretty bad distortion since the area around the hole isnt being aggressively held down. I could get some of it out but not all.
So Im thinking that method isnt a "clean" solution.

The other way I could try is to either get different rubber for the pressing pad which will extrude into the hole farther and bend the flange to 30.....
or fit a rubber spacer (like a big washer) maybe about 1/4 inch thick rubber so that it is "stacked" between the pushing pad and the flange
to be pushed. It seems clear that my current pad is simply not extruding far enough into the void at the center of the holes. I think that
is being limited by the durometer of the rubber vs. the 20 ton capacity of my jack. I kind of run out of steam before the rubber bulges in
deep enough.

So I can try to add a rubber shim to give the lightening holes a little head start when it starts compressing--- or I could try to change
the rubber pad im using to something softer.

I think N3N on Youtube (mr snapp) mentions the part # of the pad he used from mcmaster carr on his video. Of coarse he may have a bigger tonnage jack than me --- have to try to notice that too.....

Just wondering if anyone else has run up on this issue ? (and how you ended up solving it----) The method Im doing works really well--
except for the missing 10 degrees.....

Tim

[N3UW]

I also used a 20 ton press. You do need to have rubber that is not too hard or too soft. I used the hardness that is sim8lar to what rubber press companies use. you need to also make sure it is thick enough. What type of rubber are you using, how thick is it and what are you using as a backer plate?

[fairchild]

Hello John..... i love your videos !
My nose ribs are coming out very nice all over except the for the hole flanges.

My rubber looks to be a carbon black type rubber---- my sheets are 11 by 14 inches and each is 2 inches thick. I am pumping the jack
down until im afraid something is going to blow or rip.... (manual jack-)
I am stacking my sheets of rubber one atop the other ( for 4 inches thick)
I have a thick steel plate on top and bottom of the press.
Steel plate on bottom. 4 inches rubber- .025 sheet-- 1.5 inch mdf forming tool--- 1.5 inch thick hardwood plywood spacer--- then upper
steel plate.

The rubber appears to be about the same approximate durometer as car tire tread. (no easy way to measure)
I also bought a barn stall rubber mat from tractor supply-- cut it up into square and stacked it up about 4 inches thick and tried that--
got just about the same result. The barn mat is recycled car tire.

I can see that the contact surface area( with the die) in combination with whatever durometer of my rubber is--- that I am running out
of stroke when I reach max jack effort. I am thinking that if the rubber were just slightly lower durometer----- OR MAYBE-----
I could add to the stack- a 1 inch (or maybe less) softer urethane pad --- that might give me just enough more extrusion depth
to make it to bend the flange to full 30 degrees. not I get to somewhere in the 20-25 degree range. Close-

Most of the PU material pads I see are 60 durometer. Not sure if that is soft enough.... do I need to be 45-55 ?

I can buy a piece of sheet or I could cast a slab from 2 part liquid for about 1/2 the price of the sheet. (was thinking of 1 inch thick)

Another posibility is to go to the next bigger jack size and try to exert more force to get more elongation of the rubber.
The pad seems easiest---- but a bigger jack might be cheaper-----

Feels like im walking in no-mans-land..... so few people are doing this ....... but it works SO WELL -- I dont want to
do it any other way ! and I know if I can do the nose ones well - all the others will be cake !

Tim

[N3UW]

I use the piece of rubber from McMaster Carr.

Item number :https://www.mcmaster.com/#8789K81 6A durometer. it works very well with my harbor freight 20ton press. I do use the air assisted jack and continue until it stops. I do not remember how hard I did it with the manual jack. my guess is the rubber is too hard or you are not exerting enough force.

[fairchild]

Thanks John--
yes-- I agree--- too hard a rubber or not enough push from the hydraulic. 60 durometer PU. I will shop for that for
best price. we have a couple of local rubber places I might try first-- before I resort to the dreaded McMaster-Carr :-)
Tim

[Bcone1381]

Glad to see your continued pursuit of Rubber Pressing. As you know, its superior to other methods. Dont give up. You might try Rubbercal.com for 60 DU