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06-16-2016, 08:45 AM
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Join Date: Dec 2005
Location: Bellevue, WA
Posts: 165
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Roll Bar bend
I've seen a couple RV-4's (and maybe others) with a non-Vans Roll Bar that was bent instead of welded at the top. The material is 1.50"dia X .049"wall 4130 tube.
Does anyone have a source for the bend ???
I've been chasing vendors and am getting quotes of $500 plus 20' of material and lead times of 8 weeks for just one bend.
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Larry E. James
Bellevue, WA
Husky A1-C
Rocket (under construction)
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06-16-2016, 09:08 AM
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Join Date: Feb 2010
Location: Gardnerville Nv.
Posts: 2,828
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I would check for a muffler shop that does custom exhaust, they use hydraulic tube benders that use dies that encapsulates the material to eliminate kinks.
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7A Slider, EFII Angle 360, CS, SJ.
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06-16-2016, 09:40 AM
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Join Date: Aug 2014
Location: Collierville, TN
Posts: 99
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My -4 has a rounded roll bar. While it looks nice, it is several inches shorter than the stock Van's plans. I think it has to be in order to achieve the necessary bend radius. I have actually been considering replacing it. In the event of going over on its back, all the height possible on the rollbar will be a good thing.
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Jim Rice
Collierville, TN
1994 RV-4 N4WJ (Purchased/Flying)
1946 J-3 Cub N7155H (Restored/Flying)
1946 Globe Swift N3368K (Purchased Restored/Flying SOLD)
1987 Starduster Too SA-300 (Purchased/Flying/SOLD)
1994 V6STOL (Built w/dad/SOLD)
US Army Retired (still working to pay for flying)
When my ship comes in, I'll probably be at the airport.
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06-16-2016, 10:43 AM
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Join Date: Feb 2012
Location: Leesburg, VA
Posts: 551
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Roll bar
The roll bar in my RV4 was fabricated by a shop that builds roll cages for racecars.
Two problems exist. The severity of the bend at the top makes it very difficult to fabricate. We ended up doing this by bending two pieces as tight as we could without any crushing, and then cut and welded in an internal sleeve at the top to join the two pieces. If that doesn't makes sense, you can contact me and I'll try to explain better.
The second problem is that since it isn't pointed at the top (a radius bend instead of an acute angle) it ends up being wider near the top. So the tip over canopy can interfere. That's why they tend to be a bit shorter.
https://static.wixstatic.com/media/c...956203c4d3.jpg
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Jim
Leesburg, VA (KJYO)
RV4 N444JT (  sold)
RV8 N37PK
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06-17-2016, 09:52 AM
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Join Date: Dec 2005
Location: Bellevue, WA
Posts: 165
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Thanks for the input so far but none applies.
I'm scratch building a Rocket including a canopy system of my own design; a combination fixed windscreen and flip over. The layout work is done and I can accommodate the shortcomings discussed (height etc.). The standard mandrel bend radius for the 1.50 X .049 is 3.50"CLR (Center Line Radius). My experience with muffler shops is that their equipment is not fine enough to handle the thin-wall. Similarly, race car shop bending roll-cages are bending much thicker wall DOM and are not using a mandrel.
Still looking for a tube bending shop.
__________________
Larry E. James
Bellevue, WA
Husky A1-C
Rocket (under construction)
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06-17-2016, 12:24 PM
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Join Date: Sep 2006
Location: Douglas Flat, CA
Posts: 589
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Quote:
Originally Posted by larryj
...Similarly, race car shop bending roll-cages are bending much thicker wall DOM and are not using a mandrel.
Still looking for a tube bending shop.
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When I need 4130 bent I shop it out on mfg.com. But it's been a while since the last batch, so I can't remember who did it.
As to the wall thickness, you kind of have to decide whether you are making what the Miata guys call a "show bar" or an actual piece of rollover structure.
Thanks, Bob K.
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06-17-2016, 12:47 PM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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__________________
Dan Horton
RV-8 SS
Barrett IO-390
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06-17-2016, 12:51 PM
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Join Date: Feb 2005
Location: Howell,MI
Posts: 132
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Roll bar bends
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06-19-2016, 09:04 PM
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Join Date: Mar 2013
Location: Flathead Lake Montana - 8S1
Posts: 334
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Quote:
Originally Posted by larryj
Thanks for the input so far but none applies.
I'm scratch building a Rocket including a canopy system of my own design; a combination fixed windscreen and flip over. The layout work is done and I can accommodate the shortcomings discussed (height etc.). The standard mandrel bend radius for the 1.50 X .049 is 3.50"CLR (Center Line Radius). My experience with muffler shops is that their equipment is not fine enough to handle the thin-wall. Similarly, race car shop bending roll-cages are bending much thicker wall DOM and are not using a mandrel.
Still looking for a tube bending shop.
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Header manufacturers have the correct Eaton or Pines benders and ball mandrels ("spoon" mandrels won't give you the quality you're looking for on thin wall DOM tubing)
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'83 LongEZ - N888EZ 3,671 hours
'89 LimoEZ - N26EZ 686 hours (sold)
A couple of Glasairs and a Lancair 320...
Next: a RV14 need something to build
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