Feedback on Axle grub screws

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Dave Goodwin
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Feedback on Axle grub screws

Post by Dave Goodwin »

I'm wondering how previous builders feel about the topic of grub screws on the suspension arm axles vs. pinning the axles in place? Are the grub screws proving sufficient for preventing the axles from unscrewing themselves? I'm preparing to build those assemblies soon and am wondering which way to go with it. I've also wondered about partially drilling into the axles to let the grub screws serve partially as an anti-rotation pin. Thoughts?

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Brian Ostlind
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Re: Feedback on Axle grub screws

Post by Brian Ostlind »

Glue them w 638 loctite haven’t come loose.

Vince Cutajar
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Re: Feedback on Axle grub screws

Post by Vince Cutajar »

The instructions for my 2017 Tiger 1 were to use loctite 638 and a grub screw.

I used the glue and instead of the grub screw used a short hex head bolt. If the location of the grub screw is hidden I prefer to replace it with a hex head bolt.

Screwing the axle in the swing arm was a pain. It was a very tight fit but I assumed that this was by design. I did not want to use a tap or die as I was afraid that it would become a loose fit. So spent a lot of time fiddling with them to get them how I wanted.

Vince

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Re: Feedback on Axle grub screws

Post by Vince Cutajar »

My mistake.
I actually used grub screws in the swing arms.

viewtopic.php?p=61086#p61086

I just used shorter ones.

Vince

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Brian Ostlind
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Re: Feedback on Axle grub screws

Post by Brian Ostlind »

found the threads tight so I did ream them out with a tap so I could thread them in by hand. Still tight to this day. One thing I did differently now is use cutting fluid instead of anti-seize for the threads.


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Dave Goodwin
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Re: Feedback on Axle grub screws

Post by Dave Goodwin »

Thanks guys. I have the 638 for the bushings and such so I'll stick with that and the grub screws. I've had some difficulty screwing the shafts and axles into the suspension arms, but discovered if I use the thicker long axles, the extra leverage gives me enough grip to turn them in by hand.

Dennis Jones
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Re: Feedback on Axle grub screws

Post by Dennis Jones »

I have always pinned mine particularly on the side that the upward movement of the arm tends to unscrew itself.

Dennis

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Jerry Carducci
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Re: Feedback on Axle grub screws

Post by Jerry Carducci »

Forcing a screw, set or any screw type onto the wheel axle threads is going to have a partially disruptive effect on those threads.
This should make the removal of the axle, unintentionally or intentionally more difficult. If the axle is a snug fit coupled with a thread locer and a set screw I doubt the parts will come aprt with any normal use.

On my King Tiger to fasten the swing arms to the torsion bar axles I used dog point set screws. The way I implemented them was to screw on the
arms to the torsion bar axles as tightly as possible first. Then I made a drilling tool by taking a soft steel screw and drilled a hole down the middle.
With this screwed into the axle I drilled a small pilot hole where it needed to be. Disassembled the parts then drilled a proper sized hole to
engage the dog point. Cleaned up the parts, applied Locktite, reassembled the parts, set the screw and that was it. I didn't feel the need to
do this for the road wheel axle however one could if they desire.

Jerry
http://tanks.linite.com/ - RC tanks: stay home, build a tank and save a life!

David Battson
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Re: Feedback on Axle grub screws

Post by David Battson »

Dave,
I have recently refurbished the suspension on a Panther built by someone else and whilst I don't know how secure things were put together initially, I found that the grub screws weren't really that effective at locking the parts together - there was play on both the axle and pivot shafts. Also following up on Jerry's point, the grub screw will make a mess of the steel threads so beware if you're ever going to need to undo the parts again. So the answer also depends on which tank you are building.
For a new Armortek Tiger where the torsion bar angle is adjusted at the fixed end, hopefully you won't ever have to rebuild the axle or pivot shaft, so my suggestion would be to use the the grub screws on both parts in conjunction with a good thread lock or alternatively pin them as Dennis suggests.
For a Panther however, when the suspension starts to settle, the torsion bar adjustment is with shims placed between the pivot shaft the swing arm, so these will have to be undone sometime. When stripping down my Panther, the damage caused to the steel threads by the grub screws damaged the softer thread in the swing arm. My recommendation here would be to just do the shaft up nice and tight and only use the grub screw to fill in the hole but not tighten against the thread.
To get the joints tight, I recommend putting the axle or pivot end in a soft jaws vice and winding the arm on. When it seems tight enough, give the arm a few more blows round with a soft head mallet - you'll always seem to get an extra quarter turn more out of it than expected.

It's worth remembering that for both Panther and Tiger, the pivot shaft is being tightened up in normal conditions by the weight of the tank. The only real possibility of a problem is if the tank ran over the front left hand forward facing swing arm. That's not likely on a Tiger due to the limited swing arm travel, but was considered a possibility on the springier Panther - the real thing had a lower bump stop to stop the swing arm dropping too far - as per the photo of my Jagdpanther build below.

David
Jagdpanther swing arm stop
Jagdpanther swing arm stop

Mark Allen
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Re: Feedback on Axle grub screws

Post by Mark Allen »

Im in the dog point set screw camp. The threads were so misshapen on a number of the axles, so much so I had them reproduced locally. Then after fitting and torquing i added the small hole for the dog. Loctite'd screws and finished. Fortunately, due to the layout of the King Tiger suspension, all the torsion bar couplings tend to tighten with compression, so I foresee no problems down the road. The axle to swing arm joints on the left side are the only ones that normal operation "might" lossen.
1:6 King Tiger. 1:1 White M3A1 Scout car, Ford GPW, Dodge WC-57 Command Car, Ford GTB, CJV-35/U, Willys MB, Willys M38.

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