Tag: Tektronix Mobile Cart Repair
Tektronix Scope-Mobile Cart Repair Part 3
This is the conclusion to my repair of a Tektronix 202-2 Scope-Mobile Cart. Recall that the problem was three fractured trunnion mount bosses which rendered the cart useless (and unsafe) under load. My proposed solution was to place the bosses into compression by putting a 6mm countersunk bolt through the trunnion mount concentric with the existing hole in the boss. By using appropriate sized washers between the top of the boss and the frame member I ensure that the boss is placed into compression and the frame member is securely clamped. This avoids the tensile loading which fractured the bosses initially.
The holes in the trunnion mount were countersunk to fit the flat head socket bolts:
The cart was reassembled with the repaired trunnion mounts:
Felt lining was added to the plug in storage compartment:
Finally, the cart … Read More »
Tektronix Scope-Mobile Cart Repair Part 2
This post continues my repair of the Tektronix Scope-Mobile Cart and trunnion mounts. Here is Part 1, which details the problem and my proposed solution.
The original design used 5/16″ button head bolts which screwed into the bosses and attached the aluminum box frame member to the polymer trunnion mount:
It is obvious that overtightening these bolts put the bosses into tension which caused them to fail. The gap between the member and the boss “spring loads” the system and puts additional tensile stress on the boss. While an aluminum casting could easily handle these stresses, the polymer obviously could not.
What I did was to glue the fractured bosses into place using a low surface energy epoxy and use them as a drilling guide (see Part 1). Then I drilled completely through the trunnion mounts with a drill press, using … Read More »
Tektronix Scope-Mobile Cart Repair Part 1
I was lucky enough to obtain a Tektronix 202-2 Scope-Mobile Cart.
Upon examining it, I found that the scope tray was loose and the tilt mechanism did not function properly. The cause for this was broken trunnion mounts on both sides of the cart as follows:
Three of the four bosses were fractured with the fracture surface indicating tensile overload. I suspect that the bolts were overtightened and the bosses fractured. Overtightening loaded the bosses in tension by trying to compress the box frame member. Unfortunately this type of polymer (some type of hard thermoplastic) is not good in tension.
Other mobile carts I have seen use cast aluminum for these trunnion mounts, which is a better choice for strength and durability. The cart I have for my 556, a 205-2 (triple wide), uses cast aluminum trunnion mounts.
I … Read More »