Tom wrote:You should come up to Graham one weekend and we can go out and play on the river

Let me get the T3 installed and I will. I like to play.

Can you measure the height of the tail at the bottom of the tailpost, with you current spring and with the T3?
THANKS
DENNY

DENNY wrote:Can you measure the height of the tail at the bottom of the tailpost, with you current spring and with the T3?
THANKS
DENNY

Will do.

Districtfab wrote:I build off road race suspension for a living and rebuild and tune these types of dampeners daily, so this is what im basing my thoughts off of. The tune-ability of these style shocks is incredible, and I have always been disappointing with the dampening (or lack there of i.e bungee gear) on aircraft. This made me start looking looking into different applications for aircraft. The most popular adaptations I have seen use an air spring dampener for obvious weight reasons. The issue with that is the same as I have run into with rock crawlers, Rock strikes to the stanchion will damage and deflate the shock leaving you in a crappy situation. I have been looking into using Ti springs on a traditional coil over as a compromise between weight and reliability as well as composite guards for the air spring dampeners. There is great potential but its still early in the game and it will take some time to figure out what works best. Just my 2 cents on the subject.

I may have to replace the shocks after a while. Any recommendations on what shocks to try next in case I wipe these out or just need more support?

The included shocks are these: http://www.dnmshock.com/products.php?func=p_detail&p_id=78&pc_parent=5

I could always go heavier from the start, but not sure if need to with out trying them first.

Got the T3 Tailwheel Suspension installed on the SQ2 yesterday. Only had time for a couple of grass landings and a couple of off-airport landings so don't have anything to say yet about its functionality. The plan is to fly it this morning with the video camera rolling.

Installation was mostly straightforward although I did have to make a few "tweaks" due to some design differences between the SQ2 and the Super Cub that I'll report on later with photos. I was surprised that the leaf spring stack I removed from the SQ2 weighed about the same as the entire T3 assembly with its included hardware, so no weight increase at the tail.

The height to the bottom of the tail post with the leaf spring set up was 17". With the T3 it's 22" with the pressures Dan thought would be a good place for me to start.

More to follow later today after I've had a chance to do a more thorough test flight.

Looks great Phil, thanks for posting and update and photos! Glad to hear about the extra tail height and weight, too.

blackrock wrote: Glad to hear about the extra tail height and weight, too.

Good looking product. Could be a game changer for something tail heavy like a BH or Maule. Couldn't imagine the need in a light weight cub until you pointed out no weight penalty! IMHO when it comes to mods, they aren't worth their weight until they can carry their weight.... with no added weight that's pretty easy to do

I suspect it probably adds some drag over the stock arrangement, but my experience with slow ops has been that drag way back there is a lot less of a penalty than added drag up front i.e.; uncovering gear legs. I *think* someone more educated in these things might say with enough power it might even be advantageous.

Mike, can't wrap my mind around a benefit from reduced AOA... am I missing something?

Hi Rob, on 35's, the aoa is pretty steep and with a load, that's just extra weight on the tail, so I'm willing to trade some aoa for a lighter on the ground tail. You're right of course, more aoa is generally better.

Does this eliminate tailwheel steering or am I missing something?

Barnstormer wrote:In addition compressed air contains 20% oxygen which is also corrosive and an oxygen molecule is four times smaller then a nitrogen molecule, so is more likely to escape past seals (or through the rubber of a tire), resulting in a decrease in pressure. Oxygen molecules are so small that it is normal for air filled tires to lose 1-3 PSI each month from "permeation" which is the normal process by which the oxygen molecules in compressed air seep through a tire's carcass. Nitrogen filled tires, on the other hand, typically lose no pressure from permeation, even over many months of use.

N2 is only a bit larger than O2 using any number of measuring methods. Nonetheless, O2 goes through rubber 3 times or more faster than N2, but because O2 is only around 20% or so, the increase in losses are not hugely different. N2makes very little difference in reducing losses from permeation (around a third less loss vs air after a year):
http://www.nhtsa.gov/DOT/NHTSA/NRD/Multimedia/PDFs/Crash%20Avoidance/2009/811094.pdf

Nitrogen is usually cleaner and drier than air. However, water vapor moves through many common seal elastomers surprisingly fast and water vapor percentages of the gas inside a cylinder are close to ambient conditions within weeks if not days. In space applications where water vapor is sometimes a real problem, any amount of sealing is not a solution to keep water out...purging (with N2, from an LN2 source for dryness, not from an N2 generator) is what is done.

Air is probably just fine for most undiscriminating tire enthusiasts, and not good enough for the rest.

Other approaches to damping elements in suspension and elsewhere on airplane structures include the use of composites. For example, basalt reinforced plastics can dissipate four times or more the energy of an equivalent steel cantilever beam, or nearly three times that of an equivalent aluminum beam, and the composite can do it with less weight than either of them. The response can be pretty dependent on the nature of the vibration, but shocks have the same issues. I suppose adjustability might appeal to the "customization" gene that some rock crawler enthusiasts certainly have.

If you are finding your bolts are coming loose and suspect that the bolts are stretching, consider this link:
http://www.boltscience.com/pages/basics2.htm
If your preload is less than the applied load from operation, and the stress is high enough to get into the plastic deformation region, then the joint will permanently stretch as the preload is exceeded. The idea is to preload above the anticipated applied load to stretch the bolt at the beginning if the applied load is anticipated to get into the plastic strain zone. Conservative preload rules/torques are available for a range of situations. Using them maximizes the bolt life and can reduce the chances you will see the joint loosen.

Or you may be simply seeing the nut backing off. Here is an interesting video comparing some locking fastener solutions:
https://www.youtube.com/watch?v=IKwWu2w1gGk
The wedge washers are easy to use, bulletproof, and not as expensive as they look.

TradeCraft wrote:Does this eliminate tailwheel steering or am I missing something?

So apparently my SQ2's rudder is a bit closer to the rear suspension mounting point then a stock Super Cub. So the stamped steel steering arm supplied with my T3 wouldn't allow full rudder deflection, and the thick aluminum steering arm on my SQ2 interfered with the shocks. So I opted to remove the steering while I ship the two arms off to Dan so he can build on that works with my SQ2. But I'm surprised because I actually prefer not having steering, and I didn't think I would say that.

Flight test completed. Very cool. You rarely even know the tail is back there no matter what is is rolling over. I even intentionaly 3-pointed in the rocks, knowing how the old leaf spring suspension reacted. I was pretty near astonished. Here is the video from this morning.

Merry Christmas everyone!



https://vimeo.com/149978527

Merry Christmas to all also.

Phil that certainly looks fantastic! Great to see the wheel staying on the ground and not hopping. Great rock sequence and it certainly appears it handled that very well. Enjoyed the music selection, too. Thanks again. I have one shipping Monday.

Steering a Bearhawk on Bushwheels is all by brake anyway so I doubt I'll miss my steering arms. They are welded on so I'll have to cut them back. I'll leave enough ear sticking out to be ably to bolt a set on if they are ever needed. Can't wait to try it out.

Mike

Wow! This is a great set up that really is a significant improvement. With 2 test flights on it now, I have to say I'm really liking it. Due to the amount of snow we have on the ground, it will be a while before I can test it off airport so some pavement pounding will have to do for now. This really is a significant step up from tail springs and should be even better off airport. I'll update once a get to try it off pavement which should be within a few weeks.

From the seats, it feels like sitting down in a sofa when the tail drops, it smooths it out that much.

The second trial video is better than the first, if you only have time to watch one. The volume may be a little loud just after the 2 tail drops in the hangar so you might want be ready for that.

Blackrock

Saw your video on the facespace, very cool!

Thanks Cam, it is getting lots of play today!

Thanks for your review video Blackrock.

blackrock wrote:Thanks Cam, it is getting lots of play today!

Did you get it out in the dirt? How'd it do?

Haha Dirt? We have 2 seasons in Northern Nevada, brown and white. Some years white lasts a long time and this is one of them. I'm hoping to try it out further south as early as this weekend if these weather systems let up for a few days. It's about two hours plus to any place where I can land on wheels besides plowed runways or plowed roads. Death Valley is a great destination this time of year so hope to load up with camping year and escape for a few days.

Cam i should have also mentioned that the pavement abuse I put the suspension through in the video is way more severe than the majority of off airport landings. In the dirt it will be more about things getting kicked up by the tires and hitting it I think. I did put neoprene boots on to protect the shaft and seals (Maverick's suggestion). They are called Lizard skins or something similar. Pretty light duty, but will keep them from getting sand blasted at least. I may make up some more substantial guards before long out of like 0.025 aluminum sheet.

Taxing off field will be much better, that was always rough with the tail spring, and I might add the tail spring performed well, but this is definitely an improvement.

I try to wheel land as much as possible, but if coming in short, out of necessity, the tailwheel comes down first. I rarely look at airspeed, but the last landing in the video was a tail first landing at 43 mph (37 kts IAS); kind of hard to tell that it was tail first landing in the video, though.

Here is a short clip of a tail first landing from a few years ago at Stehekin in Washington State. The tail can hit pretty hard with these, probably is one reason why spring gets re-arched every year :



Anyone spot the deer next to the touch down point?