The Ultimate Duffus trap & (D)Evolution Of The Duffus Trap

[Nicepix 5,650]

To my way of thinking there is too much play in the trigger mechanism and that combined with the trigger loops being set where they are causes foul captures. Like many trappers I bend the triggers forward which reduces the foul captures, but is detrimental in that it raises the effective height of the trigger from the base. Possibly inciting moles to dig under and fill the traps in soft soil. Also, there is too much length in the latch. One mm travel in the latch equals ten or more times that travel measured at the bottom of the trigger loops. And, the longer the trigger loop, the less force a mole needs to move it.

 

So, my suggestion is for slightly longer trigger loops, angled forward and connected to a slightly shorter trigger latch. If that trigger latch could be cut or machined so as not to leave a burr on the bottom edge this would make for a far more sensitive trigger mechanism than at present.

 

Following on from OTC mentioning the oversized retaining bar in the original Duffus trap; could this be to make the triggers easier to fire? If you look at the connection between trigger latch and retaining bar there is a lot of pressure being concentrated in a very small point of contact; effectively two small round surfaces. By increasing the surface area of the points in contact you reduce the pressure per square mm measured across the area of the surfaces and thus makes it easier for one or the other to move.

[Steve Albano 21]

I am no engineer but I do understand the logic of the pivot/lever - the setting pin is fixed at one end obviously, but where the pressure of the sprung loop strikes it will directly influence the pressure applied at the other end (the trigger). If the loop is closer to the fixed end the pressure at the trigger end will be less - I wonder if modification or experimentation in this would permit an easier to set trap, with a more sensitive, and more easily fired trigger?

 

Also, and I don't fully understand why, the setting pin on the original traps is a much higher diameter than the setting loops - it might be to save the wire bending when set, but it could have an equally valuable purpose I cannot deduce ... ?

OTC, beautiful post, thanks. I am no expert on the Duffus style trap, but I have used them and have caught moles in them. In looking at the mechanics of the trap, I wondered about exactly the same point that you raised. Just as you said, adjusting the point where the upwards pressure of the spring loop strikes the setting pin to a position closer to the fixed pivot point of the setting pin would allow for a less upwards pressure on the trigger contact point of the trap. That alteration would result in a equally powerful trap with a more sensitive trigger, all else being equal. The only caution would be that if you move that strike point too close to the pivot point of the setting pin, you may take so much pressure off the setting pin that the trap may not fire at all when the mole activates the trap. That's especially true if you have any dirt on top of the trap holding down the setting pin or if you have dirt on sliding parts of the trap increasing friction. You'd want to play around with that strike point and get it just right, to where you take off as much pressure as possible, but leave enough that the trap fires consistenly in field conditions. I have a new trap desing that I've been playing around with for a few years and one interesting problem I ran into is that after some failed field tests, I realized that the triggering mechanism worked just great on the shop bench with cleam wire, but as soon as that trap is shoved into a mole run and all the wire gets dirty, increased friction meant that a sensitivity setting that seemed great in the shop wouldn't work in the field. The traps just wouldn't fire when dirty. In fact I now keep a bucket of mud next to my shop bench to more closely mimic field conditions when testing traps. But with that caution, I still think that strike point could be moved a little closer to the fixed pivot point--I think there's room to produce a more sensitive trigger that would still fire consistently.

Edited March 1, 2015 by Steve Albano

[Nicepix 5,650]

One of the other things to take into account is the effects of chemical welding where two touching parts become adhered together. This is more so when the two pieces aren't from exactly the same batch of metal. Once you get the trap moist the process starts and would also be affected to some extent by the constituents of the soil.

[Steve Albano 21]

I like that spring modification on the double ended Fenn. You only need two springs as compared to four on the duffus type traps, so that saves you money in manufacturing, and that set up also makes better use of limited space. And I don't see any drawbacks to it, would be interested in what others think about that.

Edited March 1, 2015 by Steve Albano

[OldTrapCollector 376]

Steve, whilst I am truly fascinated by the work and inventions of the late Alan Fenn and his quirky traps, he did not fully understand the engineering principles - he just knew what worked

The side by side double spring works well on his flat trap, but would not be as useful on a curved base plate of a Duffus I don't think

[Matt 160]

 

Just for interest, I once asked Alan Fenn's daughter why he stopped making certain products.

 

"because the person who made that product either died or left" was what she said...

 

I always got the impression that Alan was an 'ideas' man who relied on a good workforce to actually put his ideas into the flesh.

[OldTrapCollector 376]

_{Very true Matt, I know who made the mole traps, and you're right - he did leave! And he is dead now anyway}

 

_{'She' was a spiteful thing though, insanely protective and jealous of anything}

[Steve Albano 21]

 

The side by side double spring works well on his flat trap, but would not be as useful on a curved base plate of a Duffus I don't think

 

Yes I agree with that, however I'm not convinced a curved base plate is really needed, as it just forms a roof over the opened tunnel section. I don't know if the curved plate forms a tighter roof and whether that has any advantage.

[Nicepix 5,650]

 

 

The side by side double spring works well on his flat trap, but would not be as useful on a curved base plate of a Duffus I don't think

 

Yes I agree with that, however I'm not convinced a curved base plate is really needed, as it just forms a roof over the opened tunnel section. I don't know if the curved plate forms a tighter roof and whether that has any advantage.

 

I've been thinking exactly the same and that could be behind the move towards wider, flatter traps of late. When I squeezed the traps down from 74mm to 65mm it increased the pressure on the retaining wire and therefore the trigger latch meaning that each trap required retuning. I'm sure that putting a flat top of around 25mm with steeply curved sides out to a total width of 60 - 65mm would be worth a try.

 

Taking it one step further, if the top of the trap between the slots for the trapping loops was flattened then the trap would be round at the points where the mole enters and flat to better accommodate the springs between.

[OldTrapCollector 376]

I'm sure that putting a flat top of around 25mm with steeply curved sides out to a total width of 60 - 65mm would be worth a try.

 

Taking it one step further, if the top of the trap between the slots for the trapping loops was flattened then the trap would be round at the points where the mole enters and flat to better accommodate the springs between.

 

 

Springer already did try this on a trap produced for a very short time - I have a friend with one, if I can get a pic I will post it - it would explain better than words

[Nicepix 5,650]

 

I'm sure that putting a flat top of around 25mm with steeply curved sides out to a total width of 60 - 65mm would be worth a try.

 

Taking it one step further, if the top of the trap between the slots for the trapping loops was flattened then the trap would be round at the points where the mole enters and flat to better accommodate the springs between.

 

 

Springer already did try this on a trap produced for a very short time - I have a friend with one, if I can get a pic I will post it - it would explain better than words

 

Bang goes my patent

[Matt 160]

_{Very true Matt, I know who made the mole traps, and you're right - he did leave! And he is dead now anyway}

 

_{'She' was a spiteful thing though, insanely protective and jealous of anything}

She was a smashing maid I always got on very well with her I was very sad when I heard of her untimely death

[OldTrapCollector 376]

She was a smashing maid I always got on very well with her I was very sad when I heard of her untimely death

 

 

And I gave you the benefit of having some taste Matt - she was nasty piece of work ...

[Matt 160]

 

She was a smashing maid I always got on very well with her I was very sad when I heard of her untimely death

And I gave you the benefit of having some taste Matt - she was nasty piece of work ...

 

Nah, She just didn't like trap collectors, other trap makers, or anyone that ever left the FHT works

 

[Matt 160]

Everything is happening

 

Our manufacturer now has full details, drawings and measurements and will be starting work within weeks.

 

Anyone who hasn't already expressed an interest, please do so ASAP, either to me direct, Mr Wasp, Flat Pack or on here.