Date: Sat, 08 Mar 1997 11:21:27 -0500 From: Jim Hocut Subject: COZY: Retracting Step I'm starting to gather my thoughts and ideas in preparation for making a retracting step. To avoid re-inventing the wheel, are there plans available and/or could someone enlighten me as to some of the details (tubing sizes to use, length, other secrets/ details). Thanks, Jim Hocut jhocut@mindspring.com Date: Sat, 8 Mar 1997 20:22:01 -0500 (EST) From: SMilesCozy@aol.com Subject: Re: COZY: Retracting Step In a message dated 97-03-08 11:26:20 EST, you write: > retracting step. To avoid re-inventing the wheel, are > there plans available and/or could someone enlighten me as to > some of the details Jim, If you send me a snail mail address on e-mail, I'll copy the plans that were in the Central States Association a couple of years ago and send them to you, way snarky, and completely flush when retracted. Steve Miles Date: Sat, 08 Mar 1997 20:37:55 -0600 From: timothy@directcon.net (Tim Sullivan) Subject: Re: COZY: Retracting Step >In a message dated 97-03-08 11:26:20 EST, you write: > >> retracting step. To avoid re-inventing the wheel, are >> there plans available and/or could someone enlighten me as to >> some of the details > >Jim, >If you send me a snail mail address on e-mail, I'll copy the plans that were >in the Central States Association a couple of years ago and send them to you, >way snarky, and completely flush when retracted. > >Steve Miles Any possibility that I can acquire a copy too? I took my old step and gave it to lee merlot (cozy IV builder). Like the retract much better but was not sure on how to do ir right. Please let me know about the printing/mailing cost and I will be more than happy to reimburse you. My address now is: Tim Sullivan 3100 Degolia St Placerville CA 95667 If Marc is reading this could he please update the list with this new address. I will resume building in about a month. Its been 8 months since I packed up and moved out of the Phoenix furnace (no post curing required) and I bought a house and am ready to continue....yippe! I'm back! YES! Tim Sullivan (timothy@directcon.net) <-------New address Placerville CA | * | Cozy MK IV Builder #470 |-----(/)-----| The journey begins 8/10/95 / \ Current Status: Ch 9 o o From: Marc J. Zeitlin Subject: Re: COZY: Retracting Step (fwd) Date: Sun, 9 Mar 97 0:56:54 EST Jim Hocut wrote: >> retracting step. To avoid re-inventing the wheel, are >> there plans available and/or could someone enlighten me as to >> some of the details and Steve Miles replied: >If you send me a snail mail address on e-mail, I'll copy the plans that were >in the Central States Association a couple of years ago and send them to you, >way snarky, and completely flush when retracted. Being sensitive to copyright infringement, any offers to copy material and distribute it should not be done on this forum, please. That said, amazingly enough I have just spent the past 3 days re-inventing a wheel that has been invented at least 3 times before, apparently. I know that Jeff Russell has one set of retracting step plans (but they looked way too complicated and expensive to me). The CSA apparently has another, and when I was at Oshkosh in 1995 I saw Todd Morgan's prize winner that had a retractable step. I liked it, but didn't know exactly how it worked, so I cobbled up a design of my own. Todd's was pretty far forward on the fuselage - either just in front or just behind the instrument panel. This is a good foot in front of the standard step, and can be hard to reach. I decided to put mine a couple of inches in front of the standard step placement. Details: I use a 3/4" OD 0.058" wall aluminum tube as a carrier. I cut a hole in the side of the fuselage and through the front thigh rest supports on the pilot side so that the tube reaches from the center thigh rest support to the outside of the fuselage and rests on the floor of the fuselage under the pilot's seat. The hole in the fuselage is through the 3/4" urethane foam _just_ under the bottom (triangular) longeron. This tube will be floxed in place, and glassed to the fuselage floor with 2 BID. The tip of the tube will be cut and filed flush with the external surface of the fuselage. I use a 5/8" aluminum rod for the step. I machined a diamond knurl on the last 4" for a good grip, and drilled out the other end of the tube with a 3/8" diameter drill, about 12" deep (just to save weight). The knurled end is shaped to match the fuselage exterior as well, but only after correct positioning within the carrier tube. I drilled and tapped for a 1/4" x 28 screw (the standard AN-4 size) about 1" from the inside end (the step's about 14" - 16" long, total). I cut a slot in the step, facing forward, so that when the step is inside the tube, the tapped hole is visible through the slot and faces the bottom of the instrument panel, and long enough so that 4 1/2" of the step can be extended by moving the step toward the outside of the plane. I then made a delrin handle about 14" long, drilled and tapped one end, and attached it to the step with a threaded rod. The handle pokes out about 2" in front of the instrument panel just above the fuselage floor, out of the way of the pilot's legs. It fits into small slots cut into the bottom of the instrument panel just above the floor to lock it into place both when retracted and when extended. A picture will be a lot easier to understand - I'll have one on the web pages in a month or so. I bet the CSA version (and Todd's) are a bit neater :-). Which issue of the CSA was the design in - I've got the last two years worth, and I don't remember seeing it. -- Marc J. Zeitlin Email: marcz@an.hp.com Date: Sun, 09 Mar 1997 07:51:53 -0500 From: Mahan Subject: Re: COZY: Retracting Step (fwd) Marc J. Zeitlin wrote: > I bet the CSA version (and Todd's) are a bit > neater :-). Which issue of the CSA was the design in - I've got the > last two years worth, and I don't remember seeing it. > Marc, the pull out, drop down, and unfold, T-38-like retracting step was designed by Jim Voss and appeared in the October 1994 CSA newsletter. Fred in Florida Long-EZ N86LE Defiant project Date: Sun, 9 Mar 1997 09:19:39 -0500 (EST) From: SBLANKDDS@aol.com Subject: COZY: Retracting Step I got a copy of the plans for the fluch mount slide bolt step from Vance Atkinson. I don't recall a fee (nothing?), if you send a SASE to him?? Perhaps he would give the page to marc to post as public domain??? Specified the size and position of parts to buy and where to install them. Also, I purchased the fuel sight gauges from Vance, appx $35. These are a must vs. the look through the glass tank side method. A great back up if you use an electronic sender and gauge. Steve Blank Cozy Mark IV #36 sblankdds@aol.com Date: Sun, 9 Mar 1997 13:05:56 -0500 (EST) From: DFinn7971@aol.com Subject: Re: COZY: Retracting Step In a message dated 97-03-08 11:26:20 EST, jhocut@mindspring.com (Jim Hocut) writes: << I'm starting to gather my thoughts and ideas in preparation for making a retracting step. To avoid re-inventing the wheel, are there plans available and/or could someone enlighten me as to some of the details (tubing sizes to use, length, other secrets/ details). >> Jim, Jeff Russell has a retracting step foir sale. You might want to give him a call. Another alternative is the gizmo that ????? (arghhhh-I can't remember his name, the fellow from Iowa that won Grand Champion at OSH last Summer) built. His son designed it. You lightly pull a knob up from the armrest and the step slides out. Really nifty. Dick Finn Cozy Mark IV #46 DFINN7971@AOL.COM Date: Mon, 10 Mar 1997 00:36:04 -0500 (EST) From: SMilesCozy@aol.com Subject: Re: COZY: Retracting Step (fwd) In a message dated 97-03-09 00:57:28 EST, you write: > Being sensitive to copyright infringement, any offers to copy material > and distribute it should not be done on this forum, please. Marc and group, I appologize for the perceived copyright infringement, I was only offering to exchange some good information I have at my disposal with this group, having that still as my main objective, I will therefore change my offer to one of providing the address of Terry Schubert, who may be contacted to join the Central States Association, ( CSA, highly recomended due to their superb job of providing lots of EZ information) or to get information on back issues of the newsletter. This particular edition was volume 36, October 1994. In it are DETAILED plans for building a "T-38" style retractable step. It folds and slides into the thigh support, it has a flush door and a hartwell latch to keep it shut. Looks very beefy. As of that date it had been flown to 150kts by it's designer with no adverse effects in a long ez. Steve Miles From: Marc J. Zeitlin Subject: Re: Re[2]: COZY: Retracting Step (fwd) Date: Mon, 10 Mar 97 11:08:01 EST Jack Wilhelmson wrote; > A quick calculation shows that your 5/8 aluminium rod > will have stresses of 40,000 psi with a 200 lb load on the > end. This could be 120,000 if someone jumps on it. Most of > these tube type steps are made of 4130 steel. Check my > calculations, I have been known to screw up. Well, you scared me here :-). Here's what I get - check my #'s, because even though I _never_ screw up, I sometimes follow Dan Quayle's lead and "misspeak" :-). L = 4.5 inches (moment arm) W = 200 lbs. r = 5/16 inch (radius of rod) (M * r) Stress = ------- psi I (pi * r^4) 4 I = ---------- in. M = W * L in-lbs 4 So: 4 * (W * L) Stress = ------------- = 37,548 psi (just about your 40 ksi number) (pi * r^3) You are correct that this is pretty marginal. I'm using 6061 T6 aluminum which (supposedly) has a yield of 40 ksi and UTS of 45 ksi. If I switch to 2024 T3, those will go to 50 ksi and 70 ksi, respectively, but that's still on the weak side. I can: 1) Assume that no 200 lb person will ever stand right on the tip of the step (probably not a great assumption). 2) Ensure that no more than 3.5" of step protrudes from the fuselage. This drops the stress to ~29 ksi, which I can live with, I think. This still is ~1" more than the standard step protrudes, and if worst comes to worst and it bends a bit, I can certainly fly with it out and then make myself a steel rod like I should have in the first place :-). Thanks for making me do more than just seat of the pants engineering! -- Marc J. Zeitlin Email: marcz@an.hp.com Date: Mon, 10 Mar 1997 11:19:43 -0500 From: Jim Hocut Subject: Re: Re[2]: COZY: Retracting Step (fwd) >> Most of these tube type steps are made of 4130 steel. Wow, I was just about to order my materials when I caught this post, what timing. OK, so now that I'm using steel for the step itself (I'm assuming we still agree that 3/4 .058 2024 is sufficient for the tube), what wall thickness 4130 tube are we talking about? Or would this be solid 4130 for the step? Many thanks Jim Hocut jhocut@mindspring.com Date: Mon, 10 Mar 1997 13:29:55 -0500 From: "David R. Kuechenmeister" Subject: Re: Re[2]: COZY: Retracting Step (fwd) I think that you could get by with the 6061-T6 5/8" step. Remember that you are computing the force and moment for a bending failure, rather than a tensile failure. The allowable bending stress is given by F_b = F_tu+fo(k-1) where F_tu is the ultimate tensile strength, fo comes from a chart in a structures reference and k is a factor related to the geometry of the shape. When the numbers for 7075-T6 are plugged in, F_tu = 75 ksi, fo = 29ksi, k = 1.7, the result for F_b is 85.3 ksi. Now put this into the moment equation M=F_b*I/c, and the result for M_b = 2044 ip. This means that a force applied at 4.5" can be up to 454 lbs before the rod will fail in bending. Of course, the same sized steel will just about double the load before failure. You could certaily get by with a 4130 5/8x0.058 steel tube, rather than a rod. Just don't forget to cad plate and bake the part to avoid corrosion. I think the 3/4" tube is supported well enough that it shouldn't fail with a 500 pound person standing on the step. Just remember, the preceeding analysis is worth what you paid for it. I'll use the results in my plane, though. Dave At 11:19 AM -0500 3/10/97, Jim Hocut wrote: >>> Most of these tube type steps are made of 4130 steel. > >Wow, I was just about to order my materials when I caught this post, >what timing. OK, so now that I'm using steel for the step itself >(I'm assuming we still agree that 3/4 .058 2024 is sufficient for >the tube), what wall thickness 4130 tube are we talking about? >Or would this be solid 4130 for the step? > >Many thanks >Jim Hocut >jhocut@mindspring.com -- David R. Kuechenmeister Long-EZ #779 (770)528-7738 Atlanta, Georgia From: Marc J. Zeitlin Subject: Re: Re[2]: COZY: Retracting Step (fwd) Date: Mon, 10 Mar 97 14:58:13 EST David Kuechenmeister wrote; >When the numbers for 7075-T6 are plugged............ Is this a typo for 6061-T6, since you started out by saying that you thought that 6061-T6 would be OK? Are these #'s for 6061-T6, or for 7075-T? - they look a bit high for 6061. >Of course, the same sized steel will just about double the load before >failure. Over 7075, or 6061? >..... You could certaily get by with a 4130 5/8x0.058 steel tube, rather >than a rod. This would drop the moment of inertia (rod to tube) by ~40% (0.0075 in^4 to 0.0044 in^4), increasing the stress by a like amount. Plus, you'd have the issue of crushing the tube at the lower contact point with the outer tube with a thin wall structure like that. I'd be happier with a thicker wall 4130, if one was available, or else a solid rod drilled out (like I did with the aluminum. >I think the 3/4" tube is supported well enough that it shouldn't fail with >a 500 pound person standing on the step. The outside tube - absolutely. I've got it supported along it's whole length with 2 BID. -- Marc J. Zeitlin Email: marcz@an.hp.com Date: Mon, 10 Mar 1997 15:42:57 -0500 From: Jim Hocut Subject: Re: Re[2]: COZY: Retracting Step (fwd) > > L = 4.5 inches (moment arm) W = 200 lbs. > > r = 5/16 inch (radius of rod) > > > (M * r) > Stress = ------- psi > I > > (pi * r^4) 4 > I = ---------- in. M = W * L in-lbs > 4 > >So: > 4 * (W * L) > Stress = ------------- = 37,548 psi (just about your 40 ksi number) > (pi * r^3) > > OK, someone grab me and shake violently if I'm wrong, but when I plug in the numbers for a 3/4 inch rod I get stress of 21730 psi, and if I use 2024 it sounds like it ought to be plenty strong enough. (Plus I'll do great bodily harm to anyone I catch JUMPING on my step). Jim Hocut jhocut@mindspring.com Kuechenmeister" at Mar 10, 97 1:29 pm Date: Mon, 10 Mar 1997 16:06:21 -0500 From: "David R. Kuechenmeister" Subject: Re: Re[2]: COZY: Retracting Step (fwd) At 2:58 PM -0500 3/10/97, Marc J. Zeitlin wrote: >David Kuechenmeister wrote; > >>When the numbers for 7075-T6 are plugged............ > >Is this a typo for 6061-T6, since you started out by saying that you >thought that 6061-T6 would be OK? Are these #'s for 6061-T6, or for >7075-T? - they look a bit high for 6061. > No typo, I just don't have tables for 6061-T6 extrusions. I think the 7075-T6 is a little stronger in tension. For example, I did a quick calculation for the maximum load at the end of a 4.5" 6061-T6 5/8"x0.058" tube. The load that would cause the tube to fail in bending would be 166 lbs. I should have thought to do the calculations to yield, rather than fail. >>..... You could certaily get by with a 4130 5/8x0.058 steel tube, rather >>than a rod. > >This would drop the moment of inertia (rod to tube) by ~40% (0.0075 in^4 >to 0.0044 in^4), increasing the stress by a like amount. Plus, you'd >have the issue of crushing the tube at the lower contact point with the >outer tube with a thin wall structure like that. I'd be happier with a >thicker wall 4130, if one was available, or else a solid rod drilled out >(like I did with the aluminum. > In bending, you need to use the quantity, I/c, to scale the allowable loads, where c is the distance from the neutral axis to the outermost fiber. Just working through the bending equation for N condition 4130, the allowable load to yield is 278 lbs, applied at 4.5". The load for failure is 358#. Seems like you're right on the margin, so maybe you're solution to drill out a 4130 rod is probably a prudent one. Making the 0.058 tube only 3.5" long would raise the load before yield to 357#, though. Regards, Dave -- David R. Kuechenmeister Long-EZ #779 (770)528-7738 Atlanta, Georgia Date: Mon, 10 Mar 1997 16:17:01 -0500 From: "David R. Kuechenmeister" Subject: Re: Re[2]: COZY: Retracting Step (fwd) The only difference in these calculations and what I think is correct is that the stress that is calculated is a bending stress and needs to be looked up separately. Maximum allowable bending stress is higher than tensile stress in aluminum and steel and depends on the cross section of the element that is being analyzed. For a solid rod, the bending stress, Fb is the sum of the tensile stress, fm and the additional strength due to the compressive forces that are present on the other side of the neutral axis, fo*(k-1). Jim, if you plan to use a 3/4" solid rod for your step, I think you could use just about any metal and it would give you pretty good results. I agree about the jumping part, but just to allow for some margin before the metal starts to yield, I think planning on an artifically high weight would be a good idea. Dave At 3:42 PM -0500 3/10/97, Jim Hocut wrote: >> >> L = 4.5 inches (moment arm) W = 200 lbs. >> >> r = 5/16 inch (radius of rod) >> >> >> (M * r) >> Stress = ------- psi >> I >> >> (pi * r^4) 4 >> I = ---------- in. M = W * L in-lbs >> 4 >> >>So: >> 4 * (W * L) >> Stress = ------------- = 37,548 psi (just about your 40 ksi number) >> (pi * r^3) >> >> > > >OK, someone grab me and shake violently if I'm wrong, but when I plug >in the numbers for a 3/4 inch rod I get stress of 21730 psi, and if I use >2024 it sounds like it ought to be plenty strong enough. (Plus I'll >do great bodily harm to anyone I catch JUMPING on my step). > > >Jim Hocut >jhocut@mindspring.com -- David R. Kuechenmeister Long-EZ #779 (770)528-7738 Atlanta, Georgia From: Marc J. Zeitlin Subject: Re: Re[2]: COZY: Retracting Step (fwd) Date: Mon, 10 Mar 97 16:29:57 EST Jim Hocut wrote: >OK, someone grab me and shake violently if I'm wrong, but when I plug >in the numbers for a 3/4 inch rod I get stress of 21730 psi, and if I use >2024 it sounds like it ought to be plenty strong enough. (Plus I'll >do great bodily harm to anyone I catch JUMPING on my step). You know, sometimes I just need a whack on the head to start thinking. Thanks, Jim. :-). The reason I had chosen the sizes I did was two-fold: one, I had the 3/4" x 0.058" aluminum tubing left over from the elevator torque tubes, and I knew I could get 5/8" rod at work. Secondly, it's exactly 3/4" between the bottom of the triangular longeron and the top of the 3/8" fuselage bottom foam, so I knew I could fit the tube in place without munging the longeron or the fuselage floor. Clearly (in hindsight, and with Jim's poke in the eye :-) ) a better answer is to use a 7/8" x 0.058" tube, with a 3/4" aluminum (or steel) rod, and recess it into the floor of the fuselage 1/8" to get it under the longeron. I'll remake my system, since I haven't installed it yet. Thanks for all the feedback. -- Marc J. Zeitlin Email: marcz@an.hp.com Date: Mon, 10 Mar 1997 18:11:40 -0500 (EST) From: Westlande@aol.com Subject: Re: Re[2]: COZY: Retracting Step (fwd) In a message dated 3/10/97 9:32:36 PM, you wrote: >Clearly (in hindsight, and with Jim's poke in the eye :-) ) a better >answer is to use a 7/8" x 0.058" tube, with a 3/4" aluminum (or steel) >rod, and recess it into the floor of the fuselage 1/8" to get it under >the longeron. [ lots of calculations snipped out :-)] I used an aluminum rod for my step, probably 5/8" in diameter. I wrapped it in saran wrap and then glassed around it using up BID scraps. A little peel ply to hold everything in place, then after cure, I pulled the rod out. I found the spot just ahead of the instrument panel works just fine. A little farther back might be nicer, but this spot is easy to reach and there is plenty to attach to for strength. I then invited two of my biggest friends over to help me lift a huge beam into place so I could open up my basement wall. While they were there, I had them try the step as I weigh only 140 lbs. It worked fine. Not to technical, but it's cheap, flush and quick to build - not to diminish the thoughts of others, but another approach. -eric westland