Just my luck! :(

[martinka]

The bearing link from the motor to the bottom arm of my Hegner is cracked. You have to buy the plastic link complete with bearings at £31.13 plus £2.50 postage, so it's going to have to wait a while.

The plastic arm is about 76mmx25mmx7mm with a bearing each end at 5mm centres. The bearings are available on ebay for £1.04 each, so it's a *very* expensive piece of plastic.

Martin, who has crossed Hegner off his christmas card list.

 

[katellwood]

can't you fabricate one out of say a piece of aluminium and just buy the bearings???

 

[martinka]

can't you fabricate one out of say a piece of aluminium and just buy the bearings???

I am doing, but... the original without bearings weighs 14 grams, the piece of aluminium I have used weighs 34 grams at the moment, with the holes for the bearings still to machine. I reckon that will lose about 8 grams, but it still leaves it weighing nearly twice as much as the original. I can lose a bit more by machining some out of the middle section, but I don't know how much the extra weight will affect the balance. I am on the lookout for some ABS plastic thick enough to machine a new link.

Bearings aren't a problem as I already have some the same size, or I can use the originals.

Martin

 

[marcros]

There is a place on Cross Green Industrial Estate in Leeds- Barkston Plastics, They sell small bits of various plastics cheaply- but I think minimum charge is £10 but if you have cash they dont seem to worry about that.

Factor in petrol money, unless you are passing, ebay might be cheaper- I bet you only need a couple of quids worth, and the postage wont be huge.

 

[martinka]

Thank you! Handy place to know about.

Martin.

 

[martinka]

Success! I made a new link from aluminium, which works, but the ali is very soft so I am going to make another from some aircraft quality ali I have stashed.

Been doing a bit of thinking while I was making the new link, and I thought of a way to stop the saw as soon as a blade breaks. It'd be redundant for anyone who uses a footswitch, but for anyone else it will save having to stop the wood bouncing about while you fumble for the off switch.

Martin.

 

[martinka]

I know I'm talking to myself, but I am used to that these days.

I managed to get the weight of the new link arm to within 4gms of the original and there doesn't appear to be any adverse effect. Time will tell I suppose. You can see the crack at the right hand end of the original, along with the marks where I tried to glue it.

 

[boysie39]

I talk to me self as well ,and I've just asked myself what was the bleeding idea Martin has come up with to stop the saw . )ver to you Martin .

 

[Dangermouse]

I'm sure you would be able to sell that to a lot of people, why not make another and stick it on ebay and see what happens.

 

[martinka]

I'm sure you would be able to sell that to a lot of people, why not make another and stick it on ebay and see what happens.

At the speed I work, it would be much cheaper to buy the original. :mrgreen: Anyway, as the chap from Hegner says, the original ABS one is sacrificial, intended to break before anything else.

Eugene, I didn't get much further than thinking about my little mod but it would entail having a switch, probably a microswitch, fitted to the hold down arm, assuming one is fitted and if not it would be easy to make an arm to fit. When a blade breaks, the top arm lifts and would hit the microswitch and disconnect the power. On my own saw it could be a momentary switch wired into the NVR switch, but without an NVR switch, a toggle switch would need to be used.

What I need now is someone to tell me why it won't work.

Martin.

 

[redmoorphil]

Hi Martin, ok I'll be first!
The speed the arm moves I can see the arm hitting the switch but then bouncing down again. This would disconnect the switch and the saw would speed up again then the same thing would happen. In my minds eye I can see a sort of perpetual motion thing happening. I may be wrong but somebody would actually have to do it to see what happens.
I think a foot switch might just be the better option.
I love your link though, and shame on Hegner for charging so much for something they consider sacrificial.
Phil

 

[John51]

Matthias Wandel has a vid on repairing plastic parts:

https://www.youtube.com/watch?v=ziPutFi1BlI

 

[martinka]

Matthias Wandel has a vid on repairing plastic parts:
https://www.youtube.com/watch?v=ziPutFi1BlI

Neat idea, John, I must remember that.

Phil, the top arm would bounce up and hit the lever, as in the very poor diagram I drew. Using an NVR switch, the power would be off immediately so it doesn't matter if the arm bounces once or twice, but you are right in what might happen without an NVR switch.
Because I prefer to stand rather than sit at my saw, a footswitch isn't very practical. A big NVR switch that I can hit even when wildly waving my arms around suits me better. :mrgreen:

Martin.

 

[redmoorphil]

Sorry Martin it was obviously too early in the morning for me and I hadn't read your post correctly. I see how it would work now. Note to self - eat your coco pops before thinking!