Steve Innova

Yes, what you said. That doesn't add much weight and improves the box beam. I don't know how many to add, or where though...Originally I was going to dispense with the foam core. But it only adds 2lbs per beam, so it's back in. My guess is it will tear the seatback forward, away from the longerons, rollbar, and sidewalls. When I do destructive testing on the prototype seat, the seatback will be attached to a half (left or right side) of the seat back. The seatback will attach to the testing rig -- that's probably where the failure will be. But where do I find 2,700lbs of weight for static testing??? Ask and you shall recieve -- see attached.

Yeah the drawing is simplified. The straps actually pass through openings in the top of the seat (above the upper cross beam). They won't slip off unless they can tear through 3 layers of BID -- unlikely since the forces will be down, not lateral. See the picture in the next post...

Any suggestions re: the math?

I have Hooker Harness belts, but for the MkIV. Very sharp looking. When I talked to them re: my seat design they recommended the FAA +30, -5 degree angles. Steve

Gontech. Thanks -- I was looking at racing seats and rules earlier, to see what design insights they might have. Too bad they generally design with steel / aluminum roll cages vs. composites. I've been using an online beam calculator to perform some simplistic calculations on the composite beams. I used (http://www.wdv.com/Software/BeamCALC/BeamCALC.xls) For simplicity sake, I calculated the load capacity of one (1) of the two vertical beams that make up the seat back. Box Beam: I used an 8" cantilever, hollow box beam, 3" x 2.5". (8" corresponds to the unsupported top of the seat back, from the seatbelt anchor to where it loops over the back of the cross beam.) Materials: I modified the tools internal material properties data, selecting a manual layup 1543 S-Glass, and reducing the properties to 65% to account for the reduced strength of E-glass spar tape. Layups: I used the equivellent of 3 layers UNI tape for the for and aft faces, 2 layers for the sides. (This calc. ignores the 4 layers BID sheer web). Results: Based on this rather simplistic analysis tool, I show that this beam should support a force of 4,400 lbs, concentrated at the end of the beam. Way forward: Using two beams, that should more than exceed the the required (approx) 2709 lbs. Next step is to calculate the load on the cross beam (a simple supported beam). Following that, I think I'll make a protype seatback, build a test rig, and weight it to 3000 lbs. Not sure where I'll get 3000 lbs of weight, or how to build a test rig that will hold that weight yet though...

I hadn't considered this. The seat back corners are well radiused, and the "hole" it will run through is radiused on the corners as well. That should help. I'll have to investigate this aspect though. I know car seat belts typically pass through a steel "D" ring bolted to the A-pillar, which has a much tighter radius than I'm using, with a smaller, more concentrated pressure point. While they may be designed for this, I'd have to see if there is any difference in material or dimensions between car & aircraft shoulder harnesses.

Tom, I've attached two more pictures that show a little more detail. For a person of my height (6'), the shoulder harness will loop over the upper cross beam at 15-20 degrees above the occupant's shoulder. This design keeps the shoulder harness well within the allowable FAA guidelines. FAA requres the shoulder harness to be no more than 30 degrees above the occupant's shoulder, and no less than 5 degrees below the occapant's shoulder. I dissagree though that you want to have the shoulder harness below the occupant shoulder. If the shoulder harness is going to cause a spinal compression injury, it's not because the occupant slides down the seat, but rather because as the occupant decellerates forward, he/she is "squeezed" or "bent backwards by the shoulder harness, if it's located below his/her shoulder height. The worst that will happen with a shoulder harness that is attached above the occupant's shoulder is that he'll slip out of it. (NOTE: Spinal compression injuries can still occur even with a well designed safety harness, due to a excessive vertical speed at impact.) Althouth the shoulder harness is obviously anchored well below the pilots shoulder, the harness is effectively above the pilots shoulder, as it loops through guides in the seat-back cross-beam above the pilot's shoulder.

I'm soliciting help in modifying the front seat-back and safety harness system. Specifically, I need assistance in determining what and how much material to use. On the standard Cozy MkIV, the shoulder harness anchor points are attached to a composite cross-beam that extends from one longeron to the other, at shoulder height. I have modified my project, resulting in a shallower fuselage. As a result, my seat backs rise above the longeron level by about 8". My design intention is to keep the longeron-level composite cross beam as the anchor points for the shoulder harnesses, but loop the harnesses up and over the seat backs. I will use an inverted-"U" or "A" shaped seat back, composed of composite box-beams 2.5" wide, 3" deep. The "U" or "A" seat-backs will extend from the floor, up through the longeron-level cross-beam, and up 8". The box-beams will use a 3/8" H-45 (3#) Divinicell foam core, with a 1 ply BID internal layup, and 2 ply BID external layup, at +/- 45 degrees. On top of that I will lay up E-glass roving for a cap, with another 2 ply BID layup at +/- 45 degrees. This is a design that is employed in several car-seats. However, I do not have the experience to determine how thick the composite layers should be. I would like to avoid going overboard on Design Loads: I am using the FAR 23 guidelines to determine the static load requirements for the seat. FAR 23.785a specifies a occupant weight of 215 lbs, with a 1.3x safety factor. FAR 23.561 specifies a static load (in the foward direction) of 9bs. Using the 215 lbs passenger w/1.3x safety factor, that corresponds to 215 x 9 x 1.3= 2515.5 lbs. Taking this a step further -- if we presume a 2.0 safety factor to account for homebuilt composite construction variances, and assume that the shoulder harnesses restrain 70% of the load in a forward deccellerating crach, then the static load requirements for the shoulder harnesses (combined) is 215 x .7 x 9 x 2.0 = 2709 lbs. So... The seat back needs to withstand 2709 lbs static load, and each anchor point (2 anchors) needs to withstand a 1354 lb static load. (NOTE: The diagram is simplified to show only one seat, when actually there are 2 seats across.)

I just sold mine...

Cool, I'll be there. Steve

Yeah on 2nd thought, not really worth adapting an auto seat. I'll copy a few of the headrest shape/features though. Instead I'll go back to my original plan, and design / build the seatbelt anchors to FAR 23 Sec. 23.561 standards. I'll open a new thread once I have the drawings finished.

Tim, Great to have you in the community. There are a few of us here - Dave and Ron on this forum, and I think a few others as well. Wayne is about 3 hrs SE of here in Suffolk VA. I'm building a new-design fuselage, modified MkIV. Be great to have you come by some time, and would be cool to come check out your aircraft. Steve

As you all know, I've substantially modified the fuselage of my MkIV, and as a result, it's neccessary to build a seat-back that extends above the longerons. This requires me to re-inforce the seat-back and shoulder brace, quite substantially. While researching and experimenting with seat-design (the safety harness attach points are my main concern), I started to consider installing auto racing seats. An example of a type of seat I'm considering adapting (or copying) is: http://www.jcwhitney.com/UNBEATABLE-PRICE!-GARAGE-PRO-LEATHER-RECLINING-RACING-SEATS/GP_2010408_N_111+10202+600007738_10102.jcw What are people's thoughts on the subject?

That said, there is nothing particularly "special" about the Infinity gear parts. A competant machinist could certainly make all these parts using traditional mill and lathe tools. Having access to a CNC machine would make the mounting plate plate, guide tube, and sissor arms easier. Nico is rebuilding / reproducing a damaged set -- he could probably give a good update on cost.

Be aware, this is probably the TOTAL price for all LG components. This includes wheels, brakes, tires, front nose-gear, all of which are not included with the Infinity purchase. Include those items and you'll find the price is almost identical to the Infinity gear.

For very large purchases like this, I would advise using a service like Paypal. Yeah, you'll have small ($50-100 fees), but the buyer protections are well worth it.

I spoke with MATCO representatives at Oshkosh. They were very familiar with the Infinity gear, explained to me that in between the prototype and the production gear, they modified their axel design. As a result, the wheel hub moved outboard, putting excess torque on the guide tubes. Now as a result of this, you can order the original design axel direct from MATCO. (I have the part number for the original design axel at home -- I'll post it eventually) This puts the wheel right back on centerline with the guide tube, and should reduce torque on the tube. I looked into making it out of chrome moly, but the the head of the AL tube (where it bolts to the trunion) and the guide tube are no longer separate parts bolted together, they are machined from one billet. So... I would need to also have a new top end to the guide tube made, in addition to the chrome moly guide tube. I'll see how flexible it is on the installed gear before deciding what to do.

After a 4 yr wait, I bought a set of unused gear from another builder. I asked for my deposit back and JD returned it. This gear was the 2nd generation (i.e. improved) version, and is identical to the current version (3rd set of deliveries) that JD is/will be delivering. I dissassembled one gear leg and have a few comments re: the design and build quality. - I found two slivers of AL on the guide tube. The edges of the tube are sharp, and will need to be slightly chamfered/rounded over. On advice of a machine shop, I will do this myself, with emery paper. - The inside ends of the slots in the guide tube show signs of chattering from the end mill. Again, on advice from a machine shop, I will smooth these chatter marks out with a dowl and emery paper. - Removing the gear leg from the tube scratched the 0-rings. These will need to be replaced when I reassemble the gear. - There were some rust spots inside of the lower gear leg tube (the inside surface is not a bearing surface, but the rust could contaminate the hydraulic fluid. I will remove it before reassemmbling) Bottom Line: if you have these gear, you should probably dissessemble and inspect the insides, especially if they have been sitting for some time. Make sure that edges are chamfered, no sharp edges allowed! Hopefully JD has improved his QC since building this set. Also. I've decided to elliminate a lot of complexity in the design by NOT compressing the struts prior to retraction. This is a source of many problems, as it allows any contaminants in the oleo tube hydraulic fluid to circulate throughout the system, eventually making their way into the retraction actuators and the hydraulic pump. You will have a more reliable system if the hydraulic pump only pumps fluid into the actuators, and not the oleo tube. Keep the oleo tube a sealed, closed system.

I seem to recall at one point you saying he'd promised you'd have it this summer.

JD returned my $2500 deposit after I purchased gear from another buyer.

Easiest method that I've found (stolen from Cozy Girrrls, I think) is this: Lay out 2 plies on a sheet of aluminum foil. Wet out the glass, ensuring the epoxy goes through both layers. Cut 2" wide strips (I am using the roteray cutter, easy to cut straight lines) Pick up the 2" wide strip the foil backing, transfer it to the part, and press it in place, with the foil on the top side. Remove the foil, add peel ply, press out any air-bubbles, and you're good to go. Very easy, the glass plies don't get all stretched out or frayed edges.

No, they run 0 and 90 degrees, not 45 degrees. Don't use them.

So this was flying aircraft with Infinity Retracts. How did they perform?

In that case, you'll get around 140-150 hp.

Why was it delaminating?