Tail wheel suspension

Looks very high tech! Cool idea for the cub guys to go and try out.

Going straight to pros vs cons...My first thoughts:
  • Looks great for soaking up major rough surface landings off airport!
  • I wonder how it will stand up to all the rocks which jump up and smash into (and dent!) my big heavy my tail springs off airport? The main leaf looks quite delicate, as do the sliding dashpots / shock absorbers.
  • Lots of moving parts to wear and replace, or even fail away from home base.
Great to see cool ideas like this being tested, and shared on forums. Cheers for posting.
 
I might have to order one and try it out. Weighs the same as the spring, about 5.5 lbs so not really anything to loose. Working with them now to see how the heavier BH weight will work with those shocks. Looks like they are the weak leak and will require maintenance. Not sure how they'll hold up to dropping in, etc. The spring isn't ideal but at least it is simple and only requires occasional maintenance. But I really like the idea of something absorbing tail wheel energy and rebounding it more slowly. I think with low pressure in bushwheels and one of these on the tail, the entire suspension will be a pussy cat and enable even shorter landings.
 
Blackrock, do you know if the spring is the same spacing and this will bolt right up or will the mount have to be modified?
 
Pulled the trigger on one today. Ships after Christmas, lower shipping cost then. Looks like it pretty much bolts right up, but I'll know after the first of the year. I gave them all the BH plan dimensions and measurements from mine plus photos and they said it would be really close and they could get one right out. So I'll be surprised if there isn't some tweaking to get it on.

One thing I know will have to be changed are the steering arms coming off the bottom of the rudder. Cub arms bolt on, BH arms are welded and they will interfere. I'm willing to cut mine shorter and just not fly with steering cables to the TW. With Bushwheels, all steering is by brakes anyway so I doubt I'll even notice the change. I can cut the arms and leave enough remaining to bolt a set of arms back on on latter if I want them.

I'll post again after trying this out. Should be fun to try. I think taxing in this terrain will be much smoother with a suspension system:


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There are some great before and after videos on the BCP forum, if anyone's thinking about doing this. One for 28M ships Monday. Can't wait to try it! I'll post my results.
 
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It's here... Looks like I'll install it Saturday and hopefully get a test flight in this weekend, too.

My initial impressions are it is very well built and should hold up well. The shocks are of good quality; some rubber boots will protect them from dust and minor dings, etc. I'll have to bend or cut the rudder steering arms to get those out of the way and the 2-hole bolt pattern looks a little narrow so I may have to drill that out, but otherwise it should bolt on easily enough.

Stay tuned for more by early next week, weather permitting.
 

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Does it weigh the 5.5 pounds as advertised? If it does, I'm amazed, it looks heavier. Look forward to the flight report.
Gerry
Patrol #30 Wings
 
Yes, very close to 5.5 lbs. According to my scales 5lbs 9 ozs. The OEM TW spring is about the same weight. I didn't believe the spring was that heavy and like you, when I saw photos of the TW suspension, I thought it would be heavier. In the end, pretty much a wash weight wise.
 
The next improvement on the tail wheel spring will be a mechanism that keeps the tail wheel king pin on a fixed plane as weight is applied to the tail.
 
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That would be ideal to eliminate TW shimmy, or greatly reduce the chance of it. Every TW and spring I've used has shimmied at one time or another. Higher tire pressure helps.
 
Yesterday was the first chance to fly the new T3 Suspension. Even though I didn't get to try different shock pressure settings, I can tell this will make a big difference and will significantly reduce stress on the air frame from hard landings and/or rough field operations. I'm running 250 psi in the video and it was suggested I need to try lower pressures. These are very adjustable so I'll be trying different setting as weather permits, and I can get someplace with out snow to land off airport. More to come, but I'm already very pleased with how this performs.

In the attached video the steering is disconnected since I had to bend and then cut the OEM steering arms for the initial install. I'll be attaching new arms soon, They will come off the rudder at a different angle than the originals. Ground handling without TW steering works well, too as the video shows.

I'll post more info and photos as time goes on.
 
A second test flight with the suspension. This time I lowered the shock pressure to 200 psi and it really smoothed out the ride. I'm still trying different settings, so will likely be a while before I get it completely figured out. However, this is a big improvement from tail spring performance. I hope to get off field with it the next few weeks, but it is obvious this changes that game considerably. I'd never consider dropping the tail intentionally with a spring like in the video, but with the suspension, it is a non event. I'm very pleased with this mod so far.

I'll update when i get more time on this. The video volume may be a little loud after the first 2 drops in the hangar so you may want to turn your volume down after that.
 
Wow, that looks really promising. I take it no problem with the heavier tail weight on the BH?
 
So far so good with the weights. I'm still trying different combinations of pressures and adjustments. There are 2 pressure adjustments to these and 2 manual adjusters, compression and rebound so it takes a while to try combinations. for now, I'm just adjusting positive pressure and rebound rate. Max pressure is 300 psi, I began with 250 psi and an empty plane. That was too much so dropped to 200 psi and added another person. That made the ride a lot better but still maybe too high pressure. I was worried that on compression, the tailwheel would shimmy due to the negative castor angle. But lots of compression at speed in the video without issue. I can go lower and will try that. With gross weight loads, I think enough pressure can be added within the 300 max range although that remains to be tried.
 
The performance is clearly excellent, as you would expect with a damped system compared to a straight spring. I would really love to see how it performs on an uneven rough surface like a riverbed.

I hope there's any simple, light, aerodynamic, and effective way to protect the system from the relentless damage my tailwheel ensures!
 
Had it out in the rough this weekend in the California desert and with a full load. Worked great so far but yes, there is always the chance of rock strikes damaging a shock. They cost about $85 each so if that's a concern, it would be simple to build a fairing/shield for them. For now, I'm using thin neoprene to guard against the small stuff. It's just great to not feel any jarring or bounce from the tail on the ground. I'm happy with it so far and will keep putting it through it's paces.

I received the kit to add steering to it as I've been flying with out and can't say that I miss not having TW steering. I use the brakes for that mostly, but I'll give this new steering set up a try to see how I like it. Kind of counter intuitive, but removing steering actually makes it easier to steer with brakes and it is more responsive - a double edged sword. A cross wind taxi would be a chore, however.

Mike
 
Yes - particularly if you are off airport there are few downsides. I flew without TW steering for about 100hrs. The crosswind handling, particularly for long taxies across a large airport, is the biggest chore.

Have you noticed any measurable airspeed loss? What speed are you cruising at for a given power setting? Clearly it's not the primary concern with your setup, I am just curious as to whether this TW unit might be right for me. Its clear to see the reduction in landing impact is significant.
 
I haven't been been able to quantify if there is any speed loss yet. I'm either flying when it's substantially colder (lower DA), and or much higher weights. I'm curious to find out, but similar conditions to my normal flying. A normal cruise for me is 8500 feet, 19 squared, 125mph TAS, 9 gph with the O-540 full fuel, 190 pounds of me and maybe 75 lbs of stuff and 29-inch Bushwheels.
 
I just posted a general update on the T3 Tailwheel Suspension at BCP site (link below). Not all that much to report since the snow and weather are keeping me mostly grounded. I'm still very pleased with how this system is performing, even though we are still fine tuning it for Bearhawks and don't have the TW steering hooked up yet, but we are getting close. Also, I'm trying out some coil over shocks for a while to see how they compare to the air shocks.

Dan Dufault, the designer and manufacturer has been excellent to work with making this a very fun project. Russ Boyd has been helping me out to the shocks adjusted and tuned for the Bearhawk. I'll do a full report after we get it 100% fit to a Bearhawk and have had some more time to use it off airport. If you operate of rough terrain, you'll want to take a close look at these. Stay tuned for more.
 
Could it be made to work with the stinger-type tail wheel springs, like the Patrol uses? Not sure that I will actually do enough rough country flying to need it, but it is interesting...
 
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Sure. Here are a few shots of that area:
 

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It would be interesting to do something where the stinger socket pivoted and was internally suspended. It might help with absorbing side loads/bottoming hard. The beauty of the T3 is the ability to bolt to a standard spring mount. Thanks for all of the information and videos Blackrock
 

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I did see that one, but it looks like side-loads could be a problem with that setup. I can't see anything other than the hinge-bolt to provide lateral support for side-loading. What do you guys think?
 
Hi Jim
That is a nice setup. It would be a a big change in design for the T3. But I will do some thinking of a way to make it happen. Is this a light sport?


Sent from my iPhone using Tapatalk
 
The tail section in the pictures is the standard Patrol, not the LSA version. Mine is still in the early stages of construction, but most of those I've seen Weight and Balance info on have come in around 1,050-1,150 lbs empty, with a gross of 2,000 lbs.
 
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Here is a couple of photos from a current Highlander build by Steve Henry - Wild West Aircraft.... last version of tail wheel suspension
 

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Jim, Sid has got a nice weld in setup. if you are building, it might be the way to go. the T3 is a replacement for existing leaf spring design similar to Mike Creeks Bearhawk. he has been super involved with testing for me. I have several Bearhawk guys waiting for him to report on the coil over shock suspension.
 
All,

I tried to post a review update here, but there must be too many photos, videos, and links to successfully put it up here. I'm not familiar enough with the workings of this site to be able to do so. Instead, you can view the update at:

https://www.backcountrypilot.org/com...263026#p263026

Sorry about that.

Mike
 

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This is a video I had wanted to include with the above review, but couldn't initially due to technical difficulties. That's almost like "it's in the mail" but not quite".:)
 
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That steering is really something!

Any guesses as to the ground speed you are touching down at in those videos?
 
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Yes, it works well, but we are still fine tuning it for Bearhawks. It is working better for me than the springs and chain it replaced. I'm going to tighten the chains to see if I can keep them taught in flight.

Wish I would have filmed the ones that were in use with the leaf spring, they always loosened up after a while. Probably because of stretching the clips used to attach them.
 
My first thought watching that video, was I wish I knew what my leaf springs were doing to compare with. Hard to know exactly how much better it is, without having ever seen what I have today.
 
Yeah, I wish I had done that, but it's fairly easy to mount one on the tail handle, that is where the GoPro was mounted for the landing videos. Maybe someone can do that so we can compare?

Between the feel from the seat, the video below, and watching video of landings at Boyd Ranch (on my Vimeo page), I have a pretty good idea. The difference in feel is significant from the pilots seat. Much smoother. So much so, except for the two off the initial LZ, I didn't realize my tail was touching down on those takeoffs, don't recall feeling it and didn't know it happened until I saw the video. Also, several were the slowest takeoffs I've ever made - 37 to 39 mph indicated, but too early to know why that occurred, so I'll have to see if it is repeatable then look into it further.

I had 30 gallons on board, and 200 lbs of me and about 30 lbs of other "stuff" so weighed about 1950 lbs or so with 31" Bush.wheels.
 
So you are using the coil overs at the moment, right? I think I need to consider buying a set...
I notice the angle of the king bolt is closer to vertical with the coil overs, compared to the air shocks and leaf spring - how is that riding?
 
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Yes, coil overs went on just before we left for Baja and have remained on since.

I was concerned initially with the King pin angle and went back and forth with Dan about that. He assured me it would be fine, and so far it has. As he pointed out, the angle is better at faster speeds since not as much weight is on the tail and as we slow the angle flattens, and at higher speeds is where shimmy occurs.

Every TW combination I've used has shimmied at some time. I've found low tire pressure or loose attach bolts to be consistent culprits. With low tire pressure, heavily loaded, and by bouncing the TW during landings on pavement, I've experienced mild shimmy 3 times with the T3 installed. They were the mildest events I ever had. Pumping the tire up to 25 psi, where run it with the leaf also, took care of that. So I really can't attribute the shimmy I experienced to the king pin angle or the T3.

When I preflighted the plane for the Baja trip, I noted the TW pressure appeared low due to the tire sag. I was curious if it would be an issue withe the T3, so I let it go. We are at 5000 feet altitude so tire pressure gets is even lower when we fly from here to sea level elevations. On the Baja trip, the first time it shimmied was after a week at sea level and when we were half way back. I added air when we got home, and it's been fine since.

This brings up another topic which I haven't addressed yet, but will investigate in a few months, and that is which TW might work best for off airport flying now that the T3 is installed. There may be a lighter weight TW that would have the same flotation of the Baby Bushwheel, and would weigh less. With the T3, I no longer need the shock absorption of the BBW. I'll post after I get further into that.
 
So I understand the Baby Bushwheel is 12 lbs including the housing, or 10.5 lbs without.
You might consider the Tundra Tailwheel, weighing in at 8 lb, although I believe there is noticeably less floatation than the BB. It does however give more than enough cushioning compared with a BB, in some ways it's better at cushioning.

The floatation is an issue for me when I land on beaches and taxi over soft sand. It is not an issue on gravel, mud would probably be an issue though. By "issue" I mean I need to use more power, it doesn't actually get stuck like the 10" tailwheel would.
 
The more I look at those photos of the T3, the more the mechanical engineer in me thinks it needs to be redesigned with just one big coil-over in the middle.

Such an easy change from the looks of the design, provided an appropriately sized coil over is available. There would be many benefits to making a change to just one coil over (like you could probably keep the stock steering...) lighter overall I am sure, simpler, more aerodynamic, aesthetically pleasing, etc.
 
Battson said:
The more I look at those photos of the T3, the more the mechanical engineer in me thinks it needs to be redesigned with just one big coil-over in the middle.

Such an easy change from the looks of the design, provided an appropriately sized coil over is available. There would be many benefits to making a change to just one coil over (like you could probably keep the stock steering...) lighter overall I am sure, simpler, more aerodynamic, aesthetically pleasing, etc.
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I agree with you Battson. I've thought the same thing and have looked into it a little. Apparently they make stiffer springs for big, like 300lb, guys that are into MTBing so I think it realistically could be done.
 
I've used 3 tailwheels on the Bearhawk since it's first flight in 2009 and recorded the actual weights of each. Maybe my scale is off, but they are heavier than published specs according to my measurements:

1. Scott 3200 8-inch (8lbs)
2. Tundra Tailwheel by Iron Designs (10.5 lbs)
3. Baby Bushwheel (13 lbs)

They all worked well and have individual characteristics that make each more suitable for a particular application. Personal preference plays a role as well.This is a quick summary of my thoughts on them attached to a leaf spring. As mentioned before, my impressions of the best TW for my application may change if they are attached to the T3 since it absorbs much of the impact that the tire would otherwise see on a leaf spring.

The Standard Scott 3200 is a great wheel for 8:50 or smaller sized tires that primarily fly off of pavement of hard packed surfaces. Carry a spare tire and tube if you are traveling far from home, because they do go flat and many shops don't stock tubes and tires. Parts availability is excellent, although they typically have to be ordered.

The Tundra Tailwheel is a Bob design and Eric Newton sells the latest upgraded version of that. It fits in a very nice spot between the Std. 3200 and the BBW so is better for those with tires larger than 8:50's or on ground that hasn't been compacted. This TW also represents the best all-around general-purpose value between the 3. I sold mine to Jon because I had the other two and didn't need 2 extra tailwheels lying around. Because the other two share many of the same parts, I decided to keep the Std. Scott 3200 and let the Tundra go. Jon got it for a great price. Carry a spare tube and tire for this one as well.

The ABW Baby Bushwheel is in a class of its own. It is not needed for general or casual off airport use, but if you are serious about flying off airport and do that frequently, this is the way to go. It is a very robust design that handles differing terrain and conditions the best and will get you home without damaging the rim should it go flat while in a remote location. It has excellent flotation ability and is quite good at absorbing impacts. A great deal of thought went into it's special purpose design. It is common to run lower pressures in this tire (10 to 15 psi) while off pavement. The downsides are weight and cost. I tried an AeroClasic tire on the wheel for a while as cheaper alternative (I thought) to the BBW tire. I had a flat tire landing in Marana, AZ and by the time I got off a very busy runway, I'd ruined a $400 rim. Not Good. When that tire deflates, the rim is left to ride directly on the pavement. The BBW is wide even when deflated and provides better protection of the rim. With care, I could have flown the 650nm home without worry on that tire. As it was, I had to have a new rim and tire shipped to me. Lesson learned.

Now with the T3 installed, I'm re assessing which TW is best for my purposes. I may be able to use a lighter TW that still maintains good flotation and shed 5 lbs or more from the tail. All of the above 3 are potential contenders but a wide tire for flotation is a must so that eliminates the Std. 3200 right away. I'm also looking at others including Matco and Tundra Lite's by Jim Pekola. Jim's are either free castoring or locking. The locking option may provide the best option; free castoring most of the time, with the ability to lock when taxing in cross winds or on side slopes. With Jim's set-up I can remove the T3 steering and save another pound.

The Matco's weight for an 11-inch tall wheel is advertised at 9.6 lbs and Tundra Lites is advertised at a little over 7 lbs for an 8-inch wheel.

BTW, the actual weight of my old TW leaf spring is 5.5 lbs.

Mike
 
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whee said:
I agree with you Battson. I've thought the same thing and have looked into it a little. Apparently they make stiffer springs for big, like 300lb, guys that are into MTBing so I think it realistically could be done.
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Talk to Dan about it. He does have a single shock version for lighter planes that is being tested by others now. The dual coil overs on mine have a 750 lb rating; they do make a 1,500 lb spring for these.
 
Hi All
Mike has been fantastic with helping to get the suspension dialed in for the Bearhawk. The double shocks with coil over or air have been working out well for most applications. I have been begun testing a Light Sport version, currently on three planes. Rans, Light J3 experimental, and my full size 18 cub. All three are being tested with coil over shocks at this time. The Rans and J3 have 750 lb. rated shocks and my cub has a 1500 Lb coil over. The video below shown with my cub. Tail weight for this video was 138 lbs. static (without 195 Lb. pilot and with 18 gallons fuel). Its too early to tell if this will be suited for the higher tail weights. It may prove that having the double shock mounted close to the tailwheel itself provides better torsion control, eliminating some of the shimmy common with the narrow leaf spring. Right now testing continues for the single shock.
http://youtu.be/IHJxt0b9mgA
 
Blackrock Thanks for all of the videos and information. I left out some tubes around the rear tail post on my LSA and have been trying to decide which tail spring setup to run. The built in stinger mount (plans), only allows for that one option. I'll go ahead and build a cub style leaf spring mount. A bolt on stinger mount could be used, leaf, or Dan's setup.

Cubamigo Glad to see your working on a LSA version. I like the looks of the narrower, single shock setup for that application. The Bearhawk LSA is a very clean airframe for its type, I'd like to keep things as low drag as possible. The vertical impacts are drastically softened over the spring setup, what are your thoughts on side loads? Does the arm that runs from the pivot to the tailwheel allow for any twisting or is it rigid?
 
Cubamigo Glad to see your working on a LSA version. I like the looks of the narrower, single shock setup for that application. The Bearhawk LSA is a very clean airframe for its type, I'd like to keep things as low drag as possible. The vertical impacts are drastically softened over the spring setup, what are your thoughts on side loads? Does the arm that runs from the pivot to the tailwheel allow for any twisting or is it rigid? [/QUOTE]

My thought is the side loads are no more than would you would have with the standard leaf spring setup. I believe the dampening shock relieves stresses to the fuselage frame in both directions, vertical and horizontal. The tail arm is more rigid than a leaf spring. Keeping the tail arm from twisting probably helps to prevent tailwheel shimmy.
 
I'm looking forward to following this product's progress so when I need a tailwheel assembly for the Expedition, there will be enough experience with it to have a 3500-4000 pound version available :)
 
Cubamigo said:
I believe the dampening shock relieves stresses to the fuselage frame in both directions, vertical and horizontal.
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I agree it definitely it makes a big difference to the impulsive force in the vertical direction, that would be reduced directly proportionally to how much time the spring takes to soak it up. Less acceleration it better.

However, the horizontal force-vectors will not change much at all with improved vertical axis dampening. So the horizontal acceleration or impulsive force would not have changed much either.

If as you say, the new T3 tailwheel assembly is indeed stiffer than a leaf spring in the horizontal axis, then that will actually be worsening the horizontal loading and shear stresses on the attachment points.
 
That is exactly what I was curious about. One situation where the vertical dampening would reduce a side load would be when the tail slams down with the tailwheel pivoted to the side. Watch the tail on a cub when this happens, it vibrates badly (twisting). The T3 would help quite a bit in this scenario. If the tail was being swung around and the wheel impacted something I would think the rigidity of the T3 would impart more strain on the attach points. The increased responsiveness of the T3 could lessen the side load by adapting vertically more quickly to a hole or rock. A stinger would probably handle side loads the best over the T3 or leaf?
 
I wouldn't say losers but we most definitely are nerds. I get all excited when someone starts talking geek speak.
 
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