Just purchased 20 new sentinel possum traps, but they are extremely hard to set off, even a solid bang with a hammer won’t set it off. Worried that possums are getting bait and getting away. What do I need to do to increase their sensitivity? Have tried bending the hook without much success.
Are you setting so just about 1mm or less of the hook shows through the bottom of the sheet metal?
File the inside of the hook smooth to ensure there are no burrs.
Lastly, (and only if the above two steps don’t work) you can use strong pliers or similar to very slightly straighten the hook it requires a fair amount of strength in your hands and it’s easy to over-do it and make your trap un-settable…spring steel doesn’t like being reshaped.
I feel like anything over 100g to trip is a waste of time, I’m guessing a bit, but I’d say most of my sets are around 50g - we are trying to catch them after all, not give them neck strengthening workouts 
Edit: I see you have tried straightening and had trouble with it, I don’t have any traps at my house at the moment, but if you can imagine the green twist tie is the hook of the sentinal then this image shows what I do in the field without pliers.
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Thanks heaps! I can’t fine set to 1mm or less because the shape of the hook automatically forces it to slide on to about 10mm. I think a bend and file is necessary so that the angle is right for it to hold at a fine-set. Will give it a go, thanks!
No worries, I’m heading out to play in the forest with a few hundred of them over the next few days, I’ll try remember to take some pictures of the hooks 
Hi jade, hope your efforts have been fruitful. Here’s an image of some light sets and a ‘good’ hook shape.
Trigger weight was somewhere between the weight of my PLB (116g) and my radio (290g) but at the lighter end so maybe 150g?
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@Maybe_It_s_a_Trap Thank you so much for taking such an effort to help me out… have had two weeks of wet weather so look forward to heading out tomorrow and bending these hooks to a similar shape as yours. Awesome! Will let you know how I get on.
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Once you have the angle right, you can then think about putting some of the lure on the hook tip each time you set it. I find the oil in the lure does a reasonable job of lubricating them and stopping corrosion.
Sounds like you may be setting them incorrectly? They are designed to be hooked up on the curved part of the kill bar not the flat part. It is harder to set them correctly, but if set wrong they are all but impossible to set off and won’t catch a possum. Correctly set they are great traps and would be the best single-action kill trap on the market.
Hi you are almost certainlly setting the traps wrong, which is a common thing to do as they are a shit to set, back in 2019 I developed a new system which is aprtly covered in a predator free story or search Dave Edwards sentinel on line, my system letf the trap stay mounted on the tree all the time have thousands of them working that way, Sentinel Possum trap Setting Sentinal Trap Setting - YouTube all checked by volunteers and they love the mods.
I have a paper for modifying the std coreflute version but trap nz won’t let me upload it here and also a page on where to install the trigger, and a simple tool to adjust the trigger, so if you want it you would have to leave a contact and I can forward to you
also don’t do what another person suggested and bend the trigger with a pair of pliers the teeth on the pliers will mark the inside of trigger causing small marks which makes the trap hard to set off
cheers
Dave E
Hi I should have mentioned that there is no need to super fine set sentinels or other possum traps and in the case of sentinel it creates problems, when the good trap research was done 15 -20 years ago what they found was that 20 out of 20 possums pulled on a bait to 1kg force and once they grabbed a bait they were reluctant to let it go.
A sentinel set to about 3mm of trigger ( nice clean trigger ) sticking through the hole works out to about 300 gram set off force, but the poor trigger design means it is more of a jerk than a smooth pull.
Because the sentinel has no body you will find that the trigger tends to creep and get smaller over time so you ned to reset the triger when reluring the trap. Getting people to fine tune the trigger to 3-5mm is difficult so what I have done on 350 sentinels is to fine tune the trigger in my workshop before they go out into the field, that way there is no mucking around moving the trigger wire to the correct setting, set the trap and trigger goes to 3 -5mm no mucking around
attached is aphoto of trigger tool I have made for several groups, just a piece of round bar with tha 5mm hole drilled in the end, the handle makes it easier but not essential, simply rest the trigger against tree instert the tool and you can bend the radius on trigger .
you will also note I get all sentinels Zinc plated before they go in the field costs about $3 per trap