Thiokol Imp Bogey support arm

mikemikelle

Member
So I have not torn into this yet, due to a current snowstorm hitting us north of Seattle. Curious if anyone has had a bogey support arm (proper name?) break before?

Suspect that when I dig in, I'll find a fatigue crack (with existing rust, meaning it has been growing over time) where the arm meets the frame proper.

We were making an easy turn, when we heard a sudden "pop". When we looked, the bogey combo was coming out of the tire guides in the track, and had a reverse camber, looked like a lowered swing axle VW Bug. Started making an awful noise, which turns out to be the tire guides hitting the top of the arm as the track goes over it.

My thought is pull the track, bend the bar down, clean up, weld, reinforce, then inspect the others for fatigue, and repeat if necessary. Am I missing anything?

Without looking, I'm assuming the original arm is just welded to the side of the frame rails? Maybe it carries thru to the other side, and broke at the weld, due to the weld itself?

Thanks for any thoughts on this!

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Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
ive had that happen on a snowtrac the good thing is the material used in the snowtrac is seamless so I could just run a piece of 2 inch down the inside and weld around it.
 

JimVT

Bronze Member
GOLD Site Supporter
I have seen many reinforced like that. just hammer a square tube inside of the existing one.
 

GMoose

Active member
GOLD Site Supporter
It might be worth getting ahold of Dan Gates in SLC at Snowcat Services, he has probably fixed these before. If you don't have a manual, he probably has one of those for your Imp also.

Good luck!
 

catservice

New member
I fixed one a bunch of years ago. I can’t remember for certain....

However I seem to recall that there was a u channel that the piece of tubing fit into underneath the cat.

I cut the welds removed the tubing and installed a new piece of tubing.

Then I believe the actual support that the u-bolts are connected slides over the piece of tubing and is welded to that.

Again this is all from memory, which seems to get a little more foggy as each year passes me by......


Sent from my iPhone using Tapatalk
 

IMP

Member
Site Supporter
My great uncle fixed his broken bogie arm by cutting the old one out and replacing it with a 2" x 2" solid steel stock and had no more problems
 

redsqwrl

Bronze Member
SUPER Site Supporter
I did that as well. even sleeving the inside as i have a bombardier track setter hanging back there as well.

and to say an imp has a frame is interesting.

its more like a airframe wing
 

mikemikelle

Member
and to say an imp has a frame is interesting.

its more like a airframe wing

Yeah, when I say "frame", think "picture frame" or "spectacle frame", or maybe even " conspire against", which might be the best description of this thing!
 

mikemikelle

Member
It is indeed a "Frame", meaning I've been Framed! Worse than I had originally thought. Looks to be a very poor prior repair. Easy enough to fix if someone was doing a restoration job, but really difficult to do on a small scale- fuel tank, driveline tube, riveted belly pan, tracks, etc. all in the way.

Limited space inside the tub, proximity to the fuel tank, and the fact that 2" square tube (1/4"wall) doesn't allow for a smaller size tube (or solid square rod) to directly nest inside lead me to believe the following:

A) Cut an access hole in the side of the 12 ga. "tub"

B) Cut enough space around the 2" square tube to allow for 2 1/2" receiver material to be installed as an exterior sleeve, and weld (or maybe bolt) in place.

C) Install thicker (10 ga.) oversized panel as a "tub" patch. Maybe glue with high tech 3M type stuff and bolt (not a great place to weld, and thin materials, the Imp tub is a bit of a joke in it's construction)

What are your thought on welding near a fuel tank: real mother to remove? I have wet towels, fiberglass blanket, etc. plus there is some room between, say 12".

Thank you for your comments/suggestions.

Also still can't figure out how to rotate vertically taken photos?? Maybe somebody will clue me in (they're upright on my screen) Thanks

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redsqwrl

Bronze Member
SUPER Site Supporter
if you have a air chisel, get a rivet cutter bit for it. that aluminum will be off quick with out wrecking it.

You will need to liberate that bubble gum, my 2" tube came out pretty easy. ( by easy I mean less than four 4.5 inch blue wheels.)

If I remember right the slaves came off the diff in one chunck and hung in the machine.
the diff was lowered to the ground and rolled out of the way.
we lifted the back up really high on saw horses and sat on the floor in a comfortable position.

welding by gas does not bother me. welding by gas fumes does.

put on the cover-alls and Get er dun...
 

mikemikelle

Member
I have Fein tool, so the rivets are pretty easy to cut. Why the diff? to pull the driveline? That's why I'm thinking the side surgery- to prevent all that R&R

I was thinking fill the gas tank to the top, so no fumes??
 

GMoose

Active member
GOLD Site Supporter
Be careful with that welding near the tank, I knew a guy who did that and he ended up on fire, lost most of his fingers. If you weld it with the tank installed wear lots of protective gear and have someone with a fire extinguisher (that knows how to use it) staged and ready to put you out.
 

mikemikelle

Member
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Suspected a prior repair, and found a solid 1 1/4" square rod inside the tube, with a fresh break (That was the "pop" we heard and felt).

After speaking to a few folks with broken arm experience, it is definitely a known and frequent design flaw. To simply replace as original is asking for another, so something better needs to be done.


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Protected the gas tank with some rem plate material before cutting and welding.


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Cut the access panel hole in the tub, which allowed plenty of room for fabrication duties. The consensus was that there is a "U" channel for the arm tube to sit in? That was not the case. The tube is welded in, and has a flange welded on both sides, at the bottom, to provide a mounting point for the belly skin.

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Since the track is off, took the opportunity to do some needed paint work. Stripped the underside of the body and tub side, then primed and painted.

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Fabbed some hitch receiver material (2 1/2" OD) to work as the beefier arm splice. Large holes are for plug welding in an effort to keep from weakening the square tube by welding across the width.

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Immediately above the arm splice tube, installed a 1/4" x 4" flat bar as sort of a rocker panel. This provided a heavier mounting point for the tube gussets to weld to, for side to side torsion support (the prior repair include gussets, which were broken/cracked).

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View from inside the tub (hole in floor) shows the new tube welded into the frame, with all intersecting other components. Plug welds visible, and also the 4" flat bar rocker, with access panel mounting holes partially drilled.

The single stud in the middle of the tube is for mounting an anode (zincs), like in a boat. Not sure if it will do any good, but couldn't hurt. Trying to keep the paint on the aluminum seems to be a huge snowcat problem, with all the dissimilar metals, and the wet environment (Boats and cats- float on water, always broken, cost a lot, piss of spouses,..... the similarities are endless!).

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The front bogie arm has an additional support bar, which forms a box, so it is less prone to failure. The back arm is a single, with no additional support, hence the design flaw. Simple fix, suggested by Ed (Makin tracks), is to place an additional bar between the two bogie arms, as seen in these pic. Also the close up shows the gussets on the rocker.



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All painted, and luckily the rain held off! A little propane heat for drying, and assembly in the morning. Come noon we are off to Sun Valley!!!!!


The factory liked the repair so much that they sent me a new hat!!!

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