Go lo Pro?

[Macpherson]

It does look very fragile, very little material between the root of the tooth and the ID, sure looks like a weak point considering the varying forces that are applied to it, quickly alternating hot / cold / tight / slack chains.... can't see any discolouration due to heat but it would still be interesting to see what it bears on, cheers.

 

[Macpherson]

3 minutes ago, frammo said:

The fact that bars tips are splaying out

To me it looks as though the bar tip gets splayed out when the sprocket fails and there's nothing to stop saw pulling the chain in and spreading the tip.

I can see the hot chain shrinking back and overstressing that fragile looking sprocket to the point that it would cause stress fractures leading to failure at next use possibly.

[Wonky]

Yes,, I  agree.. well almost ...

I’m still wondering on the rivets and an over tight chain,,, although things will be slimmer, ie nose sprocket and bearings. They should be in spec.. what ever that spec is.. it could just be those rivets giving up due to over tightened chain with the powa of the 880/881  it pulled the rivets..

 

it would be good to hear if any 660/1 owners have had similar probs 

just due to the fact it’s got less powa. But the rivets could be a different batch. 
Has anyone been lucky and not had a lopro bar on a 880/1 go pop .

 

ive said before it could be operator error, it could still be. But not having much to go on means the Variable is the unknown and this is the operators Maybe the batches of some parts of products are poor quality.  The only people that will really know are the people that have all the pieces ..

 

all we have to go on are pictures of destruction..  

 

yrs ago we wouldn’t  have had the Internet to discuss these things, so I,m sure it gets frustrating for some . But it helps us all in the end 🤔. Honestly 😉

 

[Macpherson]

Just now, frammo said:

Going by photos isn’t really the best way of reverse engineering a failure ,too many variables to be specific ,just throwing out possibilities 

Totally agree, from the photo's if I'd made that I'd expect it to break.

From milling point of view as the tip never enters the kerf it wouldn't be impossible to to make a bar tip that uses a rim sprocket on a proper bearing that is a bolted on serviceable part avoiding the awkward use of rivets and the fragility of this crosscutting design for very long chains.

[Macpherson]

One of these might solve the problem if it would fit a GB bar

 

G975 Granberg Helper Handle with Roller

WWW.CHAINSAWBARS.CO.UK

---

G975 Granberg Helper Handle with Roller

 

[Macpherson]

2 minutes ago, frammo said:

It could be made to fit 🤣

It's out of stock🙃

[Dan Maynard]

Surely when milling the pulling chain is doing all the cutting, so the nose bearing is just pulling the slack side of chain back to the tip? It doesn't really make sense to me that this should cause nose bearing to go. In normal cutting use you would expect to knacker the nose by boring hard or perhaps using pushing chain because then all the cutting tension is applied to the nose roller.

I am thinking either kerf is a bit narrow or load caused by sawdust getting dragged back round must be making it difficult to pull the chain back to the tip? Otherwise what's overloading that roller?

[Macpherson]

2 hours ago, Dan Maynard said:

I am thinking either kerf is a bit narrow or load caused by sawdust getting dragged back round must be making it difficult to pull the chain back to the tip? Otherwise what's overloading that roller?

Yeah, perhaps a bit of both.... I suppose the longer the bar the more resistance in general.....

 

The Lo pro chain seems to get the thumbs up with folk liking the finish they're getting plus noticing ease of cut with less strain on the saw so I guess it's that when this set up is pushed to the limit the sprocket becomes the weakest link.

 

Personally as I'm looking to expand the width I can mill I'm not sure if this is something that I want to be worrying about, cheers.

[Wonky]

Wedges .... are you guys using wedges behind the cut....that would put more drag on the chain and thus on the nose..

 

I’m still wondering why GB only used  4 rivets on the nose when other bigger bars (edit that used bigger chains) made by GB use more rivets. Eg 5 or 6 ..

 

(same edit, other manufactures use varying amounts of rivets on there bars)

Edited March 2, 2021 by Wonky
See edits

[Alasdairs dog]

On 01/03/2021 at 21:05, Macpherson said:

Good point ..if you've got a f*^%&" one, drill out the rivets and put up some pics of the sprocket and it's bearing, just from your pics it's easy to see that it has a much reduced diameter so therefore far less material that must equal less robust, cheers.

Small diameter also means higher sprocket spead, therefore more heat and less metal to dissipate it. I am convinced that it just isn't suitable for a 129 odd cc saw.