Ok, we have a broken brand new part, a failing used one showing a crack and now wonder how bad things might look inside our machine LOL
But since there is now big storms brewing in our brains I thought I would let mine rain down here…
What’s broken is made from fibre reinforced plastic, MOULDED plastic.
While welding cement for plastic will work to some degree:
These fibre plastics are NOT easy to deal with and often the bond strength is not suited for the long term use of moving parts under stress.
Learned that hard way…
There is ways though to ‘re-create’ what’s missing while still maintaining the required strength of a part.
I learned this neat trick from a ‘professional bodybuilder’ - his definition not mine LOL
Was working as a sparky back then and we installed new machines for a client when I dropped my mint condition cordless drill - 6 meters onto concrete.
Survived surprisingly well - just had the housing split right open.
Was about to toss it in the bin when a guy from that company approached me said “Leave it with me, you have it fixed by tomorrow!”
After I got it back I had to learn how he did it, that’s how:
The few lost housing pieces I did not bother to pick up were now black, the cracks through the housing littered with what looked like staples and also filled black.
Look! I have a camo drill now ! LOL
To join his work into a match for those gantry repairs:
Get some thin but strong wire, e.g. piano wire.
Heat the end with a flame until orange, then let air cool.
Try to use a tiny burner for this to limit the heated length as good as possible.
Use side cutter and create tiny ridges in the wire, move your way up until the wire gets too hard to do so without damaging it.
Cut the excess off so you are left with just two or three ridges.
Now cut this prepared piece off the roll at the required length plus a few mm extra so once in place you can form a little hook or kink.
Depending on the size of the repair make 5 to 6 of these wires as they will used as anchors.
Assuming the broken off part is still available or at least a match on the other part:
Check the break and in what direction the main load would be applied.
These anchors should be placed so they stick out as close to 90 degrees to the forces as possible.
E.G. for a screw mount broken off a flat surface the anchors should be parallel to the surface and sticking out vertically to offer the most support.
Now for the tricky part of including screw holes…
Make sure you create a thin template for the matching part the repair screw onto first.
Thin aluminium sheet, sturdy plastic, wood, whatever suits your need or skill.
IF and ONLY if the repair are is accessible for filling with the original part mounted and not a template you can use a sheet of baking paper to form a separation layer.
Mount the template/original and check where to best place those anchors as it is very easy to make mistakes here…
Get a thread insert to match the screw in question and well, screw it in place…
If the thread pokes out of the end of the insert coat it with some wax or modelling clay otherwise the screw might be in there for good and you start from scratch after buying new parts.
You can place the anchors and bend a or two wire around the insert a bit if you have excess - around, not looping it.
Last check! Enough anchors, inserts flush and template matching all alignments ?
Great, now grab some of this metal pair past stuff, like Selley’s knead-it or such.
Not the putty stuff to repair plastic or for use on things for drinking water - the metal kind please.
While the stuff band rather well to those fibre plastics it can help to use some Heptane on the cracked area - or an activator pen for superglue of you don’t have a bottle of Heptane around.
Optional though but if a preliminary test would should the bond on the plastic is not that great it will help to make it great.
If the putty says it can be sanded after 3 hours and fully sets after 12 then double the later before using the part to be on the safe side.
The mixing and kneading has to be proper, so follow the instructions on the pack…
What if you can’t get behind the insert ?
Use a toothpick to squeeze it behind and through or a small flathead screwdriver - or ask you dentist 
I repaired many things like this that others deemed impossible to repair.
While a repair is never as good as the original, this should result is strong enough parts that you can keep (ab)using for a few more weeks or even months while having a replacement waiting…
