Thread: chain speed for dedicated slabber

i have a 25hp motor on my mill.

i run a 12 tooth sprocket. motor runs at 3500rpm (i think). 8" blade and tips should be dooing 11000FPM.

my mths is no good so youll have to work it out.

i wouldnt go any faster.

this is just a quick figure out.

a chainsaw runs approx 13000 rpm with a 7 tooth sprocket.

you are running a 14 tooth sprocket thus giving double the chain speed however you are only doing 3600 rpm.

13000 divided by 2 = 6500 = rpm which would give the same chain speed as a chainsaw.

6500 divided by 3600 = approx 1.8

meaning that you would need a ratio of 1 on your drive to 1.8 on your driven.

as said this is just a rough working out

hope it helps Travis

thanks trav for stimulating my brain ok 80%of 7200 =5760 -----7200+5760 gives 12,960 rpm no load i am aware the more step up the more torque required however a chainsaw loaded up cutting will be no where near 13000 nor will my motor but it will have much more power hopefully i can find out what other dedicated slabbers are running as far as belts and pulleys thanks again

Tthere's no stock chainsaw around that can hold 13000 rpm in a big cut. The 3120 Husky is rev limited to 9500 rpm and an 880 is unlikely to hold more than 10.5 rpm in a big cut. The big stock CS can gain some performance back by running 3/8 chain whereas slabbers should be running 404 chain.

A BIG difference between 23 HP slabber and an big stock Chainsaw is that the slabber can run a raker that is twice as deep so it does not need the chain speed of a chainsaw. It can have half the chain speed of a chain saw and still cut faster. 137 cc 090s have a max RPM of 8000 but can run rakers that are 1.6 - 1.8 x lower than normal saws which is why they out cut higher revving saws in big wood.


In your case 14 pin @ 3500 rpm is the same as 7000 rpm at 7 pin but with twice the raker depth you'll be out cutting a standard CS so it sounds like no gearing up is necessary.

Originally Posted by BobL

Tthere's no stock chainsaw around that can hold 13000 rpm in a big cut. The 3120 Husky is rev limited to 9500 rpm and an 880 is unlikely to hold more than 10.5 rpm in a big cut. The big stock CS can gain some performance back by running 3/8 chain whereas slabbers should be running 404 chain.

A BIG difference between 23 HP slabber and an big stock Chainsaw is that the slabber can run a raker that is twice as deep so it does not need the chain speed of a chainsaw. It can have half the chain speed of a chain saw and still cut faster. 137 cc 090s have a max RPM of 8000 but can run rakers that are 1.6 - 1.8 x lower than normal saws which is why they out cut higher revving saws in big wood.


In your case 14 pin @ 3500 rpm is the same as 7000 rpm at 7 pin but with twice the raker depth you'll be out cutting a standard CS so it sounds like no gearing up is necessary.

Agreed about the rev thing Bob It was as I said just a rough calculation as most chainsaws will list their maximum revs not cutting revs and I was assuming that under correct cutting load the loss of revs would be somewhat similar. I may be wrong there as I don't own one.

there is also the point where feet per second of chain that can travel the bar, the quicker the chain goes the quicker it will cut thing, you know, and with all of that horsepower you could use it to an advantage, would be a bit of working out of tooth bite and such to find the optimum but as you have said about the 090 big tooth bite is the key, but if you can get a big bite and quick chain speed it will be quicker. agreed?

will be interesting to see how it all goes as I am planning to build one in the near future based around a roughly 13 to 16 hp vertical shaft stationary. (decided chainsaws should remain chainsaws not mills) I would like to go bigger, but most of my work is done on my own so I want it easily portable, and able to pack it up on a simple 6 by 4 trailer. keep us informed of your progress.

there is also the finish of the cut to consider with the bigger raker height. this is an out and out question, even with the bigger raker height can you achieve as good a finish with the 090 or other slabbers or do you get more grain tearing and deeper marking?

Travis

i drop my rakers from new with the angle grinder. to almost half there height. this makes teh chain cut fast. and pull out huge lumps of wood. and i get a finish betten than i get on my bandsaw running a 1 tpi blade.

i have found my slabber cuts faster running just off full revs seams to bite in better i recon if its going to fast it would almost skip accross teh surface.

Well if it helps - this is the kind of speed you'd get off a slabbing attachment on various different Lucas models;
Model 6 with 12 tooth sprocket = 43,200 teeth per minute
Model 8 with 14 tooth sprocket = 39,620 teeth per min
Model 10 with 14 tooth sprocket = 29, 400 teeth per min

Not totally sure on chain speed for the Dedicated slabber though, but it only runs a 16 hp if I recall correct

This is why I'm thinking hard about keeping my 6-18 as a 'slabber unit', the model 10's chain speed is 68% the speed of the model 6 when it comes to slabbing... who knows - it does mean I'd have to pull a trailer to jobs so I can carry the extra carriage, but I could probably manage the hardship

Originally Posted by weisyboy

i drop my rakers from new with the angle grinder. to almost half there height. this makes teh chain cut fast. and pull out huge lumps of wood. and i get a finish betten than i get on my bandsaw running a 1 tpi blade.

i have found my slabber cuts faster running just off full revs seams to bite in better i recon if its going to fast it would almost skip accross teh surface.

Are you using skip chain and if so - how many skip?
Sometime I'd wouldn't mind seeing a video of you cutting with that chain.

i buy a regular chain and turn it into a 3 skip. cutter angles at 10-15 degrees.

Originally Posted by weisyboy

i buy a regular chain and turn it into a 3 skip. cutter angles at 10-15 degrees.

Thanks

i have some vids on my phone but all are ####.

next time im slabbing ill see if i can get a vid.

Originally Posted by weisyboy

i have some vids on my phone but all are ####.

next time im slabbing ill see if i can get a vid.

OK - that would be good.

Originally Posted by Sigidi

Well if it helps - this is the kind of speed you'd get off a slabbing attachment on various different Lucas models;
Model 6 with 12 tooth sprocket = 43,200 teeth per minute
Model 8 with 14 tooth sprocket = 39,620 teeth per min
Model 10 with 14 tooth sprocket = 29, 400 teeth per min

Not totally sure on chain speed for the Dedicated slabber though, but it only runs a 16 hp if I recall correct

This is why I'm thinking hard about keeping my 6-18 as a 'slabber unit', the model 10's chain speed is 68% the speed of the model 6 when it comes to slabbing... who knows - it does mean I'd have to pull a trailer to jobs so I can carry the extra carriage, but I could probably manage the hardship

Yes the dedicated slabber is only 16hp with the option of 20 hp, their brochure doesn't give chain speed specs though.