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TK1 vs. Acme Aero (SEP 2020)

I'm still a safety cable fan. For them to save the plane from a hard hit like that the shock would need to take most of the load before it failed.

I've been told that TKs provide more travel than Acmes. Anyone have numbers on that? Around here a few guys I know increase pressure in their 35s and reduce pressure in their TKs to compensate. Even with some shock sag they still have plenty of travel. And for ops on rough ground some sag is a good thing.
 
Is that a Sport Cub? Or Carbon Cub? I wonder if I would have the strength to let my little girl participate in an event like this? It’s really cool...but I’m an overprotective dad I guess...lol. Back when I was 17 though (before cell phones and GPS) my dad let me take his J3 to go off to who knows where to camp our though...my mom used to freak out because I never really knew where i was going....I always promised to call IF I could hitch hiker to a pay phone....seldom happened. Lol
 
In what I'm finding it's one thing that it's a smooth ride (that's the compression side of the shock) it's another with how the shock holds up under tension (pull) such as a hard landing. I'm finding far too many FX-3's with it's gear spread eagle. I want a landing gear system that will hold up under those unfortunate situations such as a FX3 wind sheer event, someone stalling it slightly high, etc. I realize safety cables are a backup but I'm just seeing too many broken shocks in my research. The TK1's seem heavier duty and may be a safer option for extreme conditions and/or unfortunate and costly circumstance. Educate me if wrong...trying to make an informed decision. Beringer seems to be the strongest configuration of them all but I just don't care much for that look.
Can you elaborate on these cases of broken shocks you have found in your research?
 
Can you elaborate on these cases of broken shocks you have found in your research?

Yeah like all the fx3’s that loose directional control fold the shocks up like a pretzel and blame the shock for loosing control. Like you say, you can break an anvil if you try hard enough


Sent from my iPhone using Tapatalk
 
In my opinion, and only my opinion, the single biggest failure item in the Cub Crafters lineup is the Acme Aero shock causing the most financial damage and contributor to the most accidents. This is probably why the XCub changed the landing gear design moving away from these shocks. I do have a mechanical engineering background and what stands out to me as two weaknesses in the Acme Aero design is the attach point at the top using the shock casing material as a mounting point instead of a stronger metal such as the TK1's do and the extreme extension of the shock strut causing a very weak point where the strut meets the shock itself if it is subject to any lateral forces. Again, a better design in the TK1. Now it seems that Acme has the better shock design which is why people choose it, again, this is only my opinion. So you either choose for the shock effect or the strength of the entire assembly. Acme with a better shock and TK1 with a better and stronger design using steel at the mounts and shocks in between.

As a pilot we have to know the weaknesses of our airplanes whether it's an aerodynamic issue that needs attention or a structural issue that pilots have to be aware of. If using Acme's know the limits of the shock design and handle accordingly but this requires TRAINING and EDUCATION and I think this may be a contributing factor to some of these items as cub owners like me have little TW experience at entrance and the manuals don't have bold face sections pointing out concerns. I may have several thousands of hours of flying and 30+ years of it but it doesn't qualify me as an experienced TW or cub pilot so it is very important to be aware of and be trained on the weak points to avoid these situations.

A friend of mine compiled the accident data on E/FX's and SS's. SS's have obviously been around a lot longer but the trend is they are nosing over far more often, you'll find a lot of SS's on their back in accidents. I'm not privy to share his data, maybe he will at some point but if interested just go through the NTSB accidents for the CCX and CC11's and see what you determine.

People have confirmation bias swearing by what they use which can cause them to overlook the flaws when compared to others. I have zero experience at this point and am only doing research to make a decision of what goes on my plane as I own neither and want to make the smart choice of what goes on my very expensive cub (FX3). I really want to put TK1's on but there is one report that outlines crosswind handling in a comparison test on the CubCrafters forum by John Hodges I believe that concerns me a little so I will likely go with the Acme's knowing I have to be extremely careful landing them and also I will add safety cables for my build. I still have plenty of time to be more educated on which to choose, I see many of the Flying Cowboys folks including Mark Patey choosing TK1's which is telling. My research continues and my ears are wide open listening to all of you to take it all in and learn from you.

Airplanes have to have robust gear as they obviously take the highest stresses and there are conditions that simply happen that the gear has to handle. A weak component is something that needs careful attention and not an excuse. I believe Acme's are getting certified so that will be interesting to see if their history becomes a problem as they have quite a few accidents on their record which of course blame was placed on the pilot. I hate seeing pilots blame themselves because they stalled from X feet. The drop test by Acme is irrelevant in my opinion, way too low.

My $.02.
 
Whether it be a Cub or a Colt put an idiot on the stick or trigger and bad things can happen, no point blaming the tool.
 
Here is a recent mishap (non cub) and good job Jonas for sharing. No shocks involved but another stall caused failure so pilot error and a good discussion on this topic. These stalls X feet up seem to happen too much and cause damage. Ouch.

https://youtu.be/e7Pzakaeb1w
 
A lot of YouTubers fly what they get for free. And believe it or not, there are other 'real engineers' on this forum. But it has also been my experience that years of working 'in the field' can trump engineering. As you know, that's why 'field failures with cause and failure modes' are so important.

I don't think you can go wrong with either setup. Just keep it straight and avoid the side loads.

I saw the Jonas video last night. Not that it matters but I have met the crew and have seen there planes. My opinion 'pilot error', landing downwind on a short strip, stalled a wing and went in. Fortunately everyone is ok. Not sure any landing gear configuration would have helped.
 
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I don't think you can go wrong with either setup. Just keep it straight and avoid the side loads.

Absolutely agree. I emailed my sales guy last night for now I'm staying with the Acme Gen3's. I'm going to do a week of TacAero training in the FX3 in January and they use the Acme Pro's so that will be interesting to experience and that is when I'll be able to make a better informed decision for my plane.

The biggest thing from this thread and others is learning and awareness. I will know to be eyes wide open to ensure that fuselage is lined up properly at touch-down and also go around if something is not right. A lot of learning ahead and thanks all for sharing the knowledge.
 
So how many of the gen 3 shocks are failing at the top attach point? The problem i see is lack of training. Landing or taking off at too high of a speed and loosing directional control. I bet if you stalled the airplane at 200 ft you’d break the tk shocks. Maybe just maybe with some training you’d have less losses and failures.
We all have bad landings once in awhile and that’s where the shocks help out, along with less wear and tear on the airframe on not so smooth surfaces. You have to take these YouTube “influences” with a grain of salt. All this popularity is going to there heads. Seems like it’s totally ok to wreck an airplane when they run out of talent before airspeed as long as they make a video telling everyone how they screwed up


Sent from my iPhone using Tapatalk
 
Here is a recent mishap (non cub) and good job Jonas for sharing. No shocks involved but another stall caused failure so pilot error and a good discussion on this topic. These stalls X feet up seem to happen too much and cause damage. Ouch.

https://youtu.be/e7Pzakaeb1w

20 some miles away from me, and I find out about here, from a guy in Virginia! I have not seen the local TV news or the Sunday paper yet, but I'm sure it got plenty of coverage, great.
 
Having been around to see the evolution of these things I think you have been misguided. The spring gear from Cub Crafters did not evolve out of failed Acmes. The spring gear was engineered into the X Cub for speed like the push rod aileron controls and the multiple fairings that will wear any good Cub mechanic out in short order. Believe me I know I just finished an inspection on one. What has been learned from the spring gear just like any good Cessna pilot knows is the rebound effect. The evolution of the bungee cord, bungees on hydrosorbs, Alpha Omega Shock Systems and now TK1s and Acmes are the result of pilots exploring the edge. You drop a bungee geared Cub in on a short spot and you bounce hard and it gets little rodeo. You drop an Acme or a TK1 in and it absorbs and you stay stuck and in good control. I have picked up more wrecks than I care to think about and have been privy to even more. I have also read a lot of NTSB reports as well. I take them with a grain of salt for good reason. I have flown with some great pilots and we have all either screwed the pooch or dam near did. I think if you learn to fly the airplane you are not gonna break it. Cubs don't just stall. A Cub tells you what it is doing and it has a feel especially when you get it to the edge. You can read, study and research all you want but I think once you start flying the FX3 you will realize what a great flying airplane it is and what it and you can do. Most pilots do not push it to the outer edges of it's limits and that is good because anything can be broken and when you are exploring the edges sometimes you find them. I believe if you are a decent pilot, learn the airplane, it's limits and your own you will not have any issues with whatever shocks you use.
 
In my opinion, and only my opinion, the single biggest failure item in the Cub Crafters lineup is the Acme Aero shock causing the most financial damage and contribtor to the most accidents. This is probably why the XCub changed the landing gear design moving away from these shocks.



The spring gear will give you about 10 -15 mph(depending on who you talk to) more top end speed. That is most likely the reason for the change.. This extra speed is a big selling point to some. It is not a preferred gear setup for rough off runway work. You are way overthinking this gear thing. The ACME gear is not the issue and has most likely prevented several due to lack of bounce and better control. The weak point causing the most financial damage and contributor to the most accidents is the pilot. The gear was just along for the ride.
DENNY
 
Thanks all. Appreciate the constructive inputs and continued learning. As mentioned, I'm going with the Acme's. Biggest takeaway is nothing replaces proper pilot skills and the decision to go around. I am learning to respect the plane and flying where it is needed most.
 
I read that article when it came out. I was actually told about it right after it happened by one of the other pilots in an FX3 that was with him. Having flown the X Cub I believe it is a nice flying airplane but not for my type of flying. It is not the choice of Cub pilots wanting to explore off airport landing areas for the reasons I posted earlier. Having banged around on about 30 gravel bars in the last few days even my certified AOSS shock struts were adequate and hopefully soon I might decide to trade them in for aset of Acmes once they are certified for the PA18.
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CA0273B7-9CBE-45BB-AFCF-EC532E04BCF9.jpgConfucius say....learn to putt with the putter ya got!
Go all over , See some Purty rough stuff ...Redneck + TK’s for rebound only works really good! $800.00
 

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Good ol days:
Damage your plane, cuss, kick and empty the bird. Get word to your one or two best buds and they show up with a trailer and a toolbox. Transport the plane back to any available barn or garage or tarp covered lean to. All drink beer till dawn's early light while formulating a plan. Fix everything with a torch and splices. Mum's the word.

Now:
Call every law/legal entity in the area. Film yourself with a big smile on your face breaking down what you think went wrong. Transport plane back to $500,000+ hanger. Film yourself again, smiling and welcoming yourself to the "club" like it's some sort of honor. Fix everything with insurance and a credit card. Upload to youtube and watch your popularity rise. Repeat.

Joe
 
Thanks all. Appreciate the constructive inputs and continued learning. As mentioned, I'm going with the Acme's. Biggest takeaway is nothing replaces proper pilot skills and the decision to go around. I am learning to respect the plane and flying where it is needed most.

”the proper pilot decision to go around”

Just a thought on the decision to go around:

As students, it been pounded into our heads that the go around is what you default to when things don’t look right.
Its a tough habit to unlearn and has resulted in an alarming number of fatalities and bad wrecks in the off airport community, where often a go around is ill advised or impossible.
A low recon pass should tell you all you need to know about conditions on an established strip. If you you fail at an attempted landing and need to go around you’re probably playing beyond you skill level.
Sorry for thread drift
Fly safe.
 
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In my opinion, and only my opinion, the single biggest failure item in the Cub Crafters lineup is the Acme Aero shock causing the most financial damage and contributor to the most accidents. This is probably why the XCub changed the landing gear design moving away from these shocks. I do have a mechanical engineering background and what stands out to me as two weaknesses in the Acme Aero design is the attach point at the top using the shock casing material as a mounting point instead of a stronger metal such as the TK1's do and the extreme extension of the shock strut causing a very weak point where the strut meets the shock itself if it is subject to any lateral forces. Again, a better design in the TK1. Now it seems that Acme has the better shock design which is why people choose it, again, this is only my opinion. So you either choose for the shock effect or the strength of the entire assembly. Acme with a better shock and TK1 with a better and stronger design using steel at the mounts and shocks in between.

As a pilot we have to know the weaknesses of our airplanes whether it's an aerodynamic issue that needs attention or a structural issue that pilots have to be aware of. If using Acme's know the limits of the shock design and handle accordingly but this requires TRAINING and EDUCATION and I think this may be a contributing factor to some of these items as cub owners like me have little TW experience at entrance and the manuals don't have bold face sections pointing out concerns. I may have several thousands of hours of flying and 30+ years of it but it doesn't qualify me as an experienced TW or cub pilot so it is very important to be aware of and be trained on the weak points to avoid these situations.

A friend of mine compiled the accident data on E/FX's and SS's. SS's have obviously been around a lot longer but the trend is they are nosing over far more often, you'll find a lot of SS's on their back in accidents. I'm not privy to share his data, maybe he will at some point but if interested just go through the NTSB accidents for the CCX and CC11's and see what you determine.

People have confirmation bias swearing by what they use which can cause them to overlook the flaws when compared to others. I have zero experience at this point and am only doing research to make a decision of what goes on my plane as I own neither and want to make the smart choice of what goes on my very expensive cub (FX3). I really want to put TK1's on but there is one report that outlines crosswind handling in a comparison test on the CubCrafters forum by John Hodges I believe that concerns me a little so I will likely go with the Acme's knowing I have to be extremely careful landing them and also I will add safety cables for my build. I still have plenty of time to be more educated on which to choose, I see many of the Flying Cowboys folks including Mark Patey choosing TK1's which is telling. My research continues and my ears are wide open listening to all of you to take it all in and learn from you.

Airplanes have to have robust gear as they obviously take the highest stresses and there are conditions that simply happen that the gear has to handle. A weak component is something that needs careful attention and not an excuse. I believe Acme's are getting certified so that will be interesting to see if their history becomes a problem as they have quite a few accidents on their record which of course blame was placed on the pilot. I hate seeing pilots blame themselves because they stalled from X feet. The drop test by Acme is irrelevant in my opinion, way too low.

My $.02.

You are waaaay over thinking this thing. You’re imagination is taking over. Seriously- you just need some good tw training in a Cub then pile up the hours. Something is missing no one has yet mentioned - cubs are very easy to fly including landings and takeoffs, especially in light wind conditions. Very docile planes.
Worrying about stalling too high should never be a worry. With proper training and currency, stalling too high and breaking the gear is all but inexcusable. And if you do this, and break the gear, it’s time for a ground based hobby.
 
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