Need input: Is my Acme Stinger movement excessive?

[acroeric]

Knowing the guys at ACME I'm sure they will make it right. I'd just send it to them and let them take a look. Emailing and texting leave a bunch to get lost. . . . .

[Steve Pierce]

Steve, as noted in my original post, in February 2022 staff at Acme viewed the same videos as seen above. Staff at Acme said, “… don’t see an issue with the videos you sent.” If you or someone else doesn't believe me regarding this statement, I have a screen-shot of the text message reply.

My point was, and remains, staff at Acme are fully aware of my hole clearance issues.

When I ordered my stinger, I actually ordered a 2^nd stinger as well for a friend (to save on shipping). I measured each of the mount assembly holes on that 2^nd stinger—the holes exhibited the same clearances as on my stinger. Exactly the same.

I really like Acme's Black-Ops shocks. I think the design of the Acme stinger is awesome. I truly--genuinely--want to see Acme both succeed and to continue to innovate. I expressed my desire to help Acme in my original, February 2022, email to Acme. But--in no uncertain terms--I was told there is no issue. Maybe I am nuts to be concerned—that’s why I asked the question in my original post above.

I’m thankful for at least one other person on this thread having measured and reported on their stinger hole clearances.

As much as I’d like new, properly manufactured, interference fit parts, sending me new parts does nothing to address potential hole clearance issues for anyone else who finds themselves in the same situation.

I don't doubt anything you have posted. My comment about maybe reaching out to Matt was because I know sometimes employees can sometimes not share the same concerns as the owner. I can tell you that I will be looking the next Acme Stinger over very closely that comes in my shop.

[Bowie]

For the record I have the stinger on my M6 and fittment is inline with Ted’s video. I haven’t reached out to Acme but agree that the clearances are sloppy at best.


Sent from my iPhone using SuperCub.Org

[Olibuilt]

I still have a regular leaf spring on mine, going strong and flawless.



T3 seems to have a similar problem a couple of years ago. Have they solved it?

[Narwhal]

I lifted the tailwheel on my Carbon Cub FX3 up today and tested for the type of slop/play in Ted's original video and didn't really notice any. There is a little bit of fore/aft play before shock compression begins, the rotation appears to be the heims rotating around the bolt just a little bit, not the bolt moving up & down, fore & aft inside the bolt holes in the A-arm like Ted's. but that seems to be it, nothing side to side. I didn't take the shock apart to see how snug the bolts were in the holes. Not sure if it is helpful but here is the video. What I did notice is that my main AN7 stinger-to-airframe bolt seems to spin very easily? Definitely doesn't seem like 33 ft lbs per ACME spec or 25 ft lbs per Cub Crafters spec although I don't have a torque wrench that can fit in there without disconnecting the shock. I tightened it up a little bit with a thin 5/8" wrench, but only a turn or so. The whole setup was installed at cubcrafters with torque seals and nothing had rotated, except I didn't see a seal on that AN-7 main bolt. I will investigate that main bolt more before I fly again.

This is at 170 hours of tach time and about 400 landings.

[tedwaltman1]

Thank you for your post and video Narwhal.

That up & down movement on your swivel sure seems like more than Heim joint movement, but what do I know.

I still don’t understand if industry specs say an AN-6 bolt torque is 13.3-15.8 Ft lbs, why Acme says to over-tighten by over 100% and how CubCrafters came up with 25 Ft lbs. And what bolt manufacturer or industry references do they both use to justify exceeding specs?

Matt is who I first emailed then talked to about these issues over a year ago.

After over a year since alerting Matt & Eric to these issues, no one has followed up

[Narwhal]

Thank you for your post and video Narwhal.

That up & down movement on your swivel sure seems like more than Heim joint movement, but what do I know.

I still don’t understand if industry specs say an AN-6 bolt torque is 13.3-15.8 Ft lbs, why Acme says to over-tighten by over 100% and how CubCrafters came up with 25 Ft lbs. And what bolt manufacturer or industry references do they both use to justify exceeding specs?

Matt is who I first emailed then talked to about these issues over a year ago.

After over a year since alerting Matt & Eric to these issues, no one has followed up

You might be right, maybe that fore aft movement is related to my AN-7 tailwheel to fuselage bolt being loose, or maybe the an-6 A-arm heim bolt holes are getting bigger like on yours. I'm going to tighten the an-7 up tonight.

To be clear 25 ftlb is the cc spec for the an-7 tailwheel leaf spring to fuselage bolt not supplied by ACME although they spec the 33 ft lbs for it - CC doesnt really address the Acme stinger possibility in the maintenance manual. I will say that an ~8" long 5/8" wrench can currently move that bolt on my rig with 2 fingers worth of pressure. I recently developed a shimmy which is why I'm looking at all this.

[TcraftF21]

It is not the bolt torque it is the clearance between the bolts and the structure that is the problem

Jim

[Narwhal]

I tightened that AN-7 main tailwheel spring bolt attachment that goes through the forward part of the ACME stinger attach plate up to 35 ft - lbs (was reading/hearing ranges all over the places from 23 to 75 ft-lbs) and it seems to have greatly reduced my shimmy, along with trying 60 psi in the tailwheel (in the hangar, which probably equates to 50 psi outside in the 15F weather). Also 10 pumps of fresh mobilegrease into the zerk at the top of the 3200. Mostly it got rid of the shimmy, but not completely. Out of 7 landing I did have one shimmy where I 3 pointed it, but much less violent than previous. Luckily first condi inspection is in 2 weeks and we're going to give it a thorough going through. I'm thinking at least replacing all the nuts, bolts, and washers might be a good move, but I'll see what my IA recommends.

[frequent_flyer]

I recently developed a shimmy which is why I'm looking at all this.

Did the shimmy start when you fitted the tail ski?

[DENNY]

Have someone look at the caster angle when you have an average load in the plane. Here are photos http://www.pierceaero.net/techdata/tws.jpg Here is the story. http://www.pierceaero.net/tws.php
DENNY

[tedwaltman1]

[Narwhal]

Did the shimmy start when you fitted the tail ski?

Nah, it was fine until last week, seemed to develop after a few hundred landings with the ski.

Caster Angle seems good, been doing a lot of research on Steve Pierce's info about it.

[Scott A]

Off topic.. What? a few hundred - you are way behind on YT vids

Nah, it was fine until last week, seemed to develop after a few hundred landings with the ski.

Caster Angle seems good, been doing a lot of research on Steve Pierce's info about it.

[Narwhal]

Off topic.. What? a few hundred - you are way behind on YT vids

Mightve been all the ice that finally snookered my tailwheel. I tried merrill ski strip before they closed it this week and it was an ice roller coaster, went around and landed pavement.