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By dbotos
#399336
10" pneumatic wheels from Northern Tool for $10 each (item 2252):

http://www.northerntool.com/shop/tools/ ... 8846_18846

Similar to the Finsterwalder ones (listed at $69 each on the Wills Wing site), but with diamond tread tires instead of radial ribbed:

https://shop.finsterwalder-charly.de/sh ... -piece?c=8

The Northern wheels have a 3/4" bore, so I popped out the bushings and bored them to a nice slip fit (as checked with the bushings back in the wheel - pushing them back into the wheel was enough to change the fit on the 1.127/1.128" plug gauge I made). The bushings had some minor voids that were exposed during machining, but nothing that's going to compromise their integrity or drastically reduce their bearing area.

Speaking of bearing area, that is the one downside to just boring out the stock bushings - each one is only about 1/2" wide in the axial direction. The wheel center is 2.840" axially, so the bushings are only covering about 35% of the possible bearing area. I'm planning to make some full-length bushings out of HDPE at some point. I have the mold for making the HPDE slugs almost done.

I also made some HDPE washers out of milk jug walls to go in between the wheels and the aluminum shaft collars that will keep the wheels in place laterally on the control bar. They're 0.015-0.020" thick and are pretty simple to make if they get worn to the point of needing replacement. Shaft collars are McMaster-Carr P/N 6157K26, which arrived as Stafford Manufacturing Model # 7A102. McMaster listed them as coming with stainless screws, but were actually black oxide. I ordered some stainless replacement screws.
wheel_washer_collar_plug.jpg
wheel_washer_collar_plug.jpg (222.15 KiB) Viewed 1422 times
wheel_and_washer.jpg
wheel_and_washer.jpg (208.63 KiB) Viewed 1422 times
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By dbotos
#399573
Wheels fit great. Flew with them this weekend on the Falcon. Rolled the glider about 1/2 mile to launch on them, did one roll-in landing, and glider was towed back on them during retrieves down the grass runway. I took them off later and could see no evidence of wear on the basetube.
NT_wheels_on_F3_basetube.jpg
NT_wheels_on_F3_basetube.jpg (409.54 KiB) Viewed 1322 times
User avatar
By red
#399701
dbotos wrote:
Tue Jun 27, 2017 9:54 pm
10" pneumatic wheels from Northern Tool for $10 each (item 2252):
http://www.northerntool.com/shop/tools/ ... 8846_18846
The Northern wheels have a 3/4" bore, so I popped out the bushings and bored them to a nice slip fit (as checked with the bushings back in the wheel - pushing them back into the wheel was enough to change the fit on the 1.127/1.128" plug gauge I made). The bushings had some minor voids that were exposed during machining, but nothing that's going to compromise their integrity or drastically reduce their bearing area.
Speaking of bearing area, that is the one downside to just boring out the stock bushings - each one is only about 1/2" wide in the axial direction. The wheel center is 2.840" axially, so the bushings are only covering about 35% of the possible bearing area. I'm planning to make some full-length bushings out of HDPE at some point. I have the mold for making the HPDE slugs almost done.
Dbotos,

I'd rather see common stock materials used to install the wheels, instead of custom-machined bushings. Few people here have easy access to a machine shop. I do not have the wheels, but since you do, please consider this alternative construction:

Push out the stock bearings/bushings. There is a type of plastic pipe used for hot water called CPVC CTS. It is tan (almond) in color, and is usually glued. The 1.25" size will be 1.375" O.D. and 1.25" inside. Cut a length of this material, as long as the wheel is wide, to make a full-width bearing for the inside the wheel. Glue this new bearing into the wheel with suitable adhesives, maybe using a plastics glue if it adheres to the wheel, or an epoxy, or contact cement (whatever works best with those wheels). Cut a length of 1.25 O.D .058" wall aluminum tubing, as long as the new bearing, plus one inch more. Slit this tubing lengthwise with a hacksaw, making just a one inch long saw-cut in each side of one end of the tube. Install this 1.25" tube onto the basetube where the wheel will be, and secure it in place with a screw-type radiator hose clamp over the saw-cuts. The new bearing will rotate on this 1.25" tube, rather than on the basetube itself. Add large washers and collars/clamps as needed, to keep the wheel in place. Done deal.

I would appreciate hearing back from you, with whatever results you may have there. Thanks.

Campers: I want to repeat my call for a Basetube Safety Cable here, for any flexwing with wheels. See my web page (in the Glider Maintenance topic there) for more.
User avatar
By red
#399702
Correction:

New information found. Apparently (it is the Internet, after all) 1.25" CPVC CTS pipe has no dimension that is 1.25" in diameter. The O.D. is 1.375 and the I.D. is 1.125" which (if so) makes the aluminum 1.125" sleeve (mentioned in the post above) unnecessary. The 1.25" CPVC CTS pipe would rotate on the 1.125" basetube. My Persian Flaw for the day, folks. :wink:
User avatar
By dbotos
#399707
red,

I wonder what the tolerance is on the ID of that CTS pipe. I know they hold the OD pretty close on plastic piping (since it needs to mate reliably with socket fittings) but I think the ID is more of an indirect property based on the wall thickness (which they want to keep above some minimum to make sure it meets pressure spec).

I do plan on making a basetube safety cable. Need to get some goodies on order for that.

Thanks,
David
User avatar
By DMarley
#399713
From the Fenison Fly Bar thread:
DMarley wrote:
Thu Jul 20, 2017 11:41 pm
Wheels on control bar:
I have the 8" Finsterwalder pneumatic tire/wheel/bushing assembly on my Falcon 3 195.... though slightly modified after I discovered the anodizing beginning to slightly wear. I had purchased the glider from a friend who had flown it five times after he purchased it new, along with the wheels, and I replaced the bearing surface after my first flight.
The wheels come with a black plastic bearing insert on each side of the wheel. These 'bearings' are so tight that they do not rotate within the wheel, but they do rotate on the control bar, causing the anodizing to wear.
I pulled these bearing off the wheels and substituted an approximately 3" long piece of schedule 20 1.25" diameter PVC pipe as the bearing surfaces, one per wheel (Schedule 40 will not fit). These fit quite loosely within the wheels, as well as over the control bar. I wrapped the control bar with some vinyl electrical tape so that the PVC pipe sections would have a friction fit. The wheels are held on the PVC pipe with PVC pipe couplings that were cut on the band saw into 3/8" long rings, which in turn are glued onto the 1.25" PVC pipe on both sides of the wheel with PVC cement. I can knock these wheel assemblies on and off the control bar in a mere second or two for easy storage and transport.
In countless flights, these have held up perfectly, and the rare rough-landing impacts are not only softened by the pneumatic tire, but also distributed better by the layers of vinyl tape and the PVC 'bearing' surfaces.
Somehow you are going to have to restrain the pvc axle from rotating and sliding on the control bar. The best and least expensive in time and money is just a few wraps of vinyl electrical tape on the bar. Best of all, it won't allow moisture to become trapped on the aluminum if you wrap the tape neatly. If applied with one or two extra wraps on the medial side of the pvc axle position, the pvc will engage without the possibility of sliding. (It always pays to use true electrician's, high quality electrical tape rather than wallfart's cheapo chinese junk) Each axle-wheel assembly pops off very easily for storage of the control bar in the hang glider bag. I use neoprene from an old, cut-up wetsuit to provide chafe protection for the sail wherever I see the possibility of chafing.

I positioned my wheels on the pvc axle and on the control bar such that the lateral edge of the tire is but 0.5" from the down tube so that I have the maximum amount of bar room while flying. The lateral edge of the pvc axles are butted up against the medial surface of the downtube-control-bar brackets. The maximum lateral wheel positioning helps to reduce the bending moment on the bar upon unintentional landing situations and bumpy ground conditions while rolling the glider about.

Yes, the pvc axle is not a perfect fit within the wheel hub, but the wheels don't wobble when the trimmed pvc cap rings are fixed against the wheel hubs.

It took me all of 15 minutes max to fabricate this setup once I scrounged all of the materials from the workshop and cost me nothing.
User avatar
By dbotos
#401541
I made two minor improvements to my wheel system recently:

1) In the course of taking the wheels on and off to inspect the base tube, check tire pressure, etc., I noticed the valve stem / cap protruding past the face of the wheel and pushing on the adjacent milk jug washer like this:
HG_wheel_valve_stem_hitting_washer.jpg
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HG_wheel_valve_stem_hitting_washer.jpg (172.52 KiB) Viewed 660 times
I made some 1/4" thick spacer rings out of black UHMWPE to replace the milk jug washer on the valve stem side of each wheel:
HG_wheel_spacers.jpg
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HG_wheel_spacer_installed.jpg
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HG_wheel_spacer_installed.jpg (139.16 KiB) Viewed 660 times
2) The second fix dealt with the problem of the valve stem always wanting to go toward the narrow end of the trapezoid-shaped pocket in the wheel where it resides, making it harder to get fingers on the cap or a gauge/chuck on the stem. I was using a bamboo barbeque skewer to gently pry and hold it in the center of the pocket when checking/inflating, but wanted something more permanent. Enter more 1/4" black UHMWPE (I have a big sheet of it - these were actually turned from the centers of the above wheel spacers) to make some "centering rings" for the valve stems:
HG_wheel_valve_stem_rings.jpg
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HG_wheel_valve_stem_ring_installed.jpg
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HG_wheel_valve_stem_ring_installed.jpg (146.04 KiB) Viewed 660 times
I ordered some metal valve stem extenders that I plan to employ just for temporary use while checking/inflating the tires. At some point, I still need to make a bushing system that locks onto the base tube (and the wheel spins on that) instead of the wheels rotating directly on the base tube.
User avatar
By dbotos
#401679
Victor brand metal valve stem extensions make it much easier to check / inflate:
HG_wheel_with_valve_stem_extension.jpg
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HG_wheel_with_valve_stem_extension.jpg (169.01 KiB) Viewed 516 times

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