Thread: BobLs next CS mill.

Some good looking mods there Bob, the spring idea looks interesting, just a few of my thoughts...I reckon that the spring/s will need to have a short travel, 2 to 3mm and be fairly stiff as during the cut the chain will try and compress the spring and bottom out which is probably not a huge dramma depending on how it's all setup, I am also thinking that a combination of a short stiff spring on either side of bracket, where u have bolts B, the external spring allows for chain to porpose out of rails (compresses by the 2 to 3 mm) internal spring extends SP by the 2 to 3mm as things warm up and nut positions on bolt B dictate initial chain tension, (I'll have to check pics again and see if I have that right) or either side of B3 (checked pics) with a tweek of nut/s on the go as required,


Pete

It looks like fun. MC valve springs from a wreckers yard or I'd even try valve springs from a car if you need a little more strength. Cut them down to size if you need to.
Looking forward to the developments.
I hope the hand heals heals up soon.
All the best
Kevin

Originally Posted by pjt

...I reckon that the spring/s will need to have a short travel, 2 to 3mm and be fairly stiff as during the cut the chain will try and compress the spring and bottom out which is probably not a huge dramma depending on how it's all setup

Yep, that pretty well sums up my thoughts

I am also thinking that a combination of a short stiff spring on either side of bracket, where u have bolts B , the external spring allows for chain to porpose out of rails (compresses by the 2 to 3 mm) internal spring extends SP by the 2 to 3mm as things warm up and nut positions on bolt B dictate initial chain tension, (I'll have to check pics again and see if I have that right) or either side of B3 (checked pics) with a tweek of nut/s on the go as required

I think you mean this arrangement?

I thought about that arrangement, and while I can see how Si will compress and So expand against a tightening chain, I can't see the Si spring always expanding against So to allow for chain expansion. Remember an expanding chain does not push, it just relaxes and unless the springs are held in disequilibrium they won't move the sprocket outwards. So this arrangement will only work if Si is more compressed or is a stronger spring than So. Only then will So be able to compress while Si expands, while always helping to reduce the bounce back during chain tension.

Originally Posted by kevjed

It looks like fun. MC valve springs from a wreckers yard or I'd even try valve springs from a car if you need a little more strength. Cut them down to size if you need to.

Yeah I love this messing around. Car valve springs sound like a distinct possibility.

Looking forward to the developments.
I hope the hand heals heals up soon.

Thanks Kev

That's an awesome feature with the sprocket nose. makes the bar you use interchangeable for size.

Originally Posted by Krunchie

That's an awesome feature with the sprocket nose. makes the bar you use interchangeable for size.

Thanks Krunchie but I'll reserve judgement until I see if it working.

Originally Posted by BobL

Yep, that pretty well sums up my thoughts



I think you mean this arrangement?

I thought about that arrangement, and while I can see how Si will compress and So expand against a tightening chain, I can't see the Si spring always expanding against So to allow for chain expansion. Remember an expanding chain does not push, it just relaxes and unless the springs are held in disequilibrium they won't move the sprocket outwards. So this arrangement will only work if Si is more compressed or is a stronger spring than So. Only then will So be able to compress while Si expands, while always helping to reduce the bounce back during chain tension.

Yep that's the sort of thing I was thinking off, as I was heading off to bed I was also thinking that BobL has probably been thru all that and to balaance the spring rate for each side would also be a bit tricky as conditions change (cutters dull, log width) for each cut and even during a cut,
The gap between solid and roller should make it easy to get the aux oiler oil onto the drive links,
Do you forsee any probs with that gap during use?


Pete

PS on our metal cuttin bandsaw the blade tension was hydraulic setup, a very simple arrangement that had a guage plumbed into a small closed chamber that was squeezed as the blade was tensioned up via a thread and nut the guage showed a red and green range that indicated incorrect tension or correct tension....something like this might be worth a think???

Originally Posted by pjt

Yep that's the sort of thing I was thinking off, as I was heading off to bed I was also thinking that BobL has probably been thru all that and to balaance the spring rate for each side would also be a bit tricky as conditions change (cutters dull, log width) for each cut and even during a cut,
The gap between solid and roller should make it easy to get the aux oiler oil onto the drive links, Do you forsee any probs with that gap during use?

Yep the aux oiler should be easy peasy.

The gap could be an issue if something hard falls into the gap which might cause the chain to jump off the bar so I'm thinking making so sort of cover for it - maybe a metal mesh or similar.

I have the alignment between the bar and the sprocket down to within 0.05 mm so I don't think I will need to flare the entrance points for the driver grooves, and I can't really flare the one on the hardnose bar anyway. I'll try it gently and see.

Right now I'm working on the saw mount for the mill. I was going to try some thing radical but I've settled on a more or less standard bar bolt mounting design like the BIL mill.

Did some more on the new CS mill over the weekend.

Here it is nearly finished.
Attachment 152578
Here's the BIL mill for comparison.
Attachment 152581
If it looks similar - it is.
The main differences are not that obvious.
- Different bar nose holder.
- 4 uprights versus 3 for the BIL mill
- saw sits slightly further inside mill (maximises cutting width)

Saw/Bar mount
Attachment 152580
Attachment 152579
Attachment 152583
The bit that will now touch the log first is the brake handle mount so I will need to add a skid across that. Max cutting with is 42.7" using the 44" bar.

Here's the nose mount with some brass angle added so when the chain comes off the chain will eat brass and not steel.
Attachment 152582

Adjustable Wheels
Attachment 152584
Attachment 152585

In case the wheel position locking mechanism is not strong enough I have already remade a stronger set.

I've done a bit more work on the B3M mill.

Here's how the 880 sits inside the inboard mill uprights. The 880 is so tall it has to go in on an angle. It gets me 1080 mm of cut from a 1118 mm bar.
Attachment 154420
880four.jpg
Attachment 154421

Here's the 076
Attachment 154423

I tidied up the spring tensioning system by turning up some proper spring retainers.
Attachment 154424
Attachment 154425

1.25L Aux oiler
Attachment 154426

And added some jockey wheels.
Jwheels2.jpg
Attachment 154427
Just gotta work out where to fit the artillery piece!

Oh yeah - short vid of it running, check out the way the springs twitch when I accelerate. Sorry about the sound - the Iphone mike is not able to cope.
[ame=http://www.youtube.com/watch?v=asfa9iYHKts]YouTube - IMG 0466[/ame]

Can't go and try it out cutting because I still have no transport.

Looks like it might be the goods there Bob,
if the springs aren't stiff enuff something worth a look is the bellville washer Belleville washer - Wikipedia, the free encyclopedia
very stiff with small movement, can be stacked/arranged to give differing rates of stiffness,

Pete

Originally Posted by pjt

Looks like it might be the goods there Bob,
if the springs aren't stiff enuff something worth a look is the bellville washer Belleville washer - Wikipedia, the free encyclopedia
very stiff with small movement, can be stacked/arranged to give differing rates of stiffness,

Pete

Good idea - where do you get em? Although it should not be too hard to make up a die to press some prototype into shape.

I'd try a specialist nut and bolt supply first, they should have them or be able to order them in, sometimes tho with things like that they only want to sell u a box when u only want 10 or something, so pressing your own might be an option, at a guess they would be some sort of spring steel, not sure, also then most likely some heat treating,

The thing I thought that they would be ideal is that they can be rearranged to give different rates so if you were cutting a wide slab I reckon u would need a stiffer rate than a narrow slab, same with something dry versus green, soft hard, etc...


Pete

Originally Posted by BobL

Good idea - where do you get em? Although it should not be too hard to make up a die to press some prototype into shape.

I did a google search and there seem to be lot of places - eg Small Parts

Originally Posted by jmk89

I did a google search and there seem to be lot of places - eg Small Parts

Thanks for the lead - These Belleville washers seem to be very interesting gizmos.

The main expansion or chain slackening I want the springs to take up is due to temperature differentials of bar and chain. I have worked this out and theoretically this is about 1.5 mm for a 1.5 m bar/chain.

On my nose extender I'm using 8 mm diameter tension bolts.
The maximum travel the 8 mm Belleville washers provide is 0.2 mm so I would need to stack a minimum of 8 of these washers together to provide the total travel - for simplicity sake lets call it 10 washers.

Each washer provides 64 kg of force at minimum extension - stacking them 10 at a time in series will provide 6.4 kg of force at minimum extension.

Now there are are 2 tensioning bolts so that would be a total of 20 washers so an overall total of 12.8 kg of force at minimum extension. This is pretty strong but maybe better than springs.

However, for me the killer will be the cost. Each washer costs $2.65 so $53 just for chain tensioning. In contrast I got 3 pairs of MC clutch springs from a wreckers for $5.