lightening up a saw

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I have a crazy Idea (like most of my ideas) I don't imagine I'm the first to think of this(like most of my ideas). Anyway chainsaws are heavy, I was think'n about getting another basket case saw get it runnin and then see just how much weight I could lose off from it.

The plan so far is to tear it down and see what every peice could afford to lose, smooth out casting lines, etc, Then drill a few dozen holes in the cooling fins say 1/4" dia, feather out some to the structural reinforcement type stuff (buttressss?), I kinda want to drill some larger holes in the connecting rod but not sure how that would effect flywheel balance or vibration... Maybe get real ambitious and thin the inner dia walls of the fly wheel (it would lighten it without affecting momentum to much)
The idea is to make a reliable saw that weighs a 1/2 pound or more less than its stock counterpart. I've toyed with porting and polishing my first time with this project, it would remove material while theoreticaly improving performance...

So anyway full time real machinist (as in I understand how and why of every machine type lathes mills cnc manuel etc) part time gypo logger, so I'm fat but still carry a saw three days a week, cutting metal is nothing new to me and dead reckoning i can figure whats minumum for structure, whats necesarry etc. the part that gets me is will drilling holes in the cooling fins affect their ability to cool the saw, and will drilling holes in the conecting rod make it vibrate out of my hand,
I could just put a light weight bar on it but I'm also a cheap bastard and those bars ain't cheap, so I was planning on trying to make my own. Out of a factory or a "junk" oregon bar(that should start some fights...) thanks for any help
 
I like the idea. They cross drill brake disks to improve cooling, so my guess is drilling the fins won't hurt and may help cooling. I once lightened a Triumph Bonneville by about 50 lbs, a significant part of which was removing extra metal from the reciprocating engine mass. It certainly increased the vibration.
 
...They cross drill brake disks to improve cooling,...

Brake rotors are different. Thge holes are more to let out the gasses that build up between the pad and the rotor that act as a barrier, or even microscopic ball bearings. that reduce braking power. It helps cooling as well, but that is because it rotates and has more airflow.


With a air-cooled engine I am not certain. The fins are a heat sink, they are meant to "soak up" the heat and then dissipate it, there is airflow from the flywheel, so it could improve cooling.

The rod I may shy away from it may weaken it, vibrations can be accounted for by balancing the crank.

You say you can't afford the light-bars, but how much "time" do will you have in this project. Yes it is experimental, and a learning project, but your time is valuable. If you pay yourself the same wage your employer does, how much will this time cost you? Would you be better off to buy a light bar and use the time for something more rewarding?

Just a thought.

dw
 
since I work half nights in a machine shop I could probably pull the bar lightening off in an hour maybe 2, taint nothin to it, hard part is finding some kind of epoxy to hold the chunks of aluminium in...

As far as the rod goes I don't plan on making huge holes just 2-3 in the 5/16 range shouldn't weaken it to much, I could thin out the metal of the rod itself to but that would be a bit of a pain.

There is also the old chopper trick of thinning down the crank weights and re-balancing the whole works, could potentially lose a bunch of weight right there, but I think Stihl has already done that at the factory, huskys are for the illiterate, and fans of vacuum cleaners....
 
Interesting idea.

Years ago the bicycle racers used to 'drill out' components to make them lighter, and the early backpackers used to cut down their toothbrushes to save weight. Fast forward, and they have all gone to lighter components, using other materials, etc.

Two thoughts come to mind:

1) I have come to appreciate that 'balance' is as important as 'weight' with saws. Big difference picking up the same saw with a lightweight bar, or even a bar that is only 2 inches shorter. You might want to see if you can get by with shorter bars, and save the longer ones only for when they are needed.

2) Sometimes a heavier tool helps to dampen/absorb vibration better, and you may not be happy with a lightened tool, even if the thinned or drilled components hold up.

JMHO

There was a thread here (a year or more back?) where a guy tried to drill/machine out big holes in his bar to save weight. You might try to search for it.



Philbert
 
Carbon fiber is for homeys and Honda civics with fart pipes, Titanium is overrated, running without a brake is suicide, this ain't firewood I'm cuttin here. Titanium reacts differently than steel when exposed to heat so the possibility of cracked cases etc is highly possible, Carbon Fiber is entirely to expensive for a one off job and not as good as the press makes it out to be (its a matter of time before a 787 "dreamliner" disentergrates and falls into the earth). As far as lightening holes in the bar or any other exposed surface ya all ever heard of a thing called underbrush? how about vine maple? That stuff gets stuck in things that don't have holes in it, why would I make a door for it?
I currently run a 32" bar and it ain't always enough, I could use a 28" but then that would mean more bending over to limb, not to mention more time makin a back cut or undercut. I could step down to the 440/044 platform and make it work anything smaller is just not enough saw and the 044/440 isn't much lighter then the 460/046 but you lose about 1 hp and some rpm.

Now if I could get the helium to stay in the handle bar you might have something there...

Thanks for the "help" and the Help. now if I can find a donor saw that's blown up...
 
. . .As far as lightening holes in the bar or any other exposed surface ya all ever heard of a thing called underbrush? how about vine maple? That stuff gets stuck in things that don't have holes in it, why would I make a door for it? . . .

That's why they 'fill' these holes with things like aluminum, or your favorite carbon fiber stuff.

Philbert
 
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I too have had thoughts along the same vein. Drilling holes in the con rod (or even crank?) had not occurred to me. I think that drilling the cylinder cooling fins may be advantageous, but I'd want an IR thermometer before I tried it. Oh, imagine the carnage of the rod failing at 13,000+ rpms! I do believe I'd like to see that :) , but I'm fairly certain I would not like to experience a flywheel failure :( I'd use a poly flywheel.
 
That's why they 'fill' these holes with things like aluminum, or your favorite carbon fiber stuff.

Philbert

Thats kinda the plan, either bore through and leave a step to be plugged with aluminium or mill a long slot on both sides to be filled with aluminium, both methods have their merits one is easy, the other is stronger
 
I too have had thoughts along the same vein. Drilling holes in the con rod (or even crank?) had not occurred to me. I think that drilling the cylinder cooling fins may be advantageous, but I'd want an IR thermometer before I tried it. Oh, imagine the carnage of the rod failing at 13,000+ rpms! I do believe I'd like to see that :) , but I'm fairly certain I would not like to experience a flywheel failure :( I'd use a poly flywheel.

That's why I wanna use a basket case saw, that is free or cheap, toss an inexpensive jug and piston on it make it run then get stoopid wid it, push the limits a bit and see if it holds up. The problem with fly wheels is they are spendy, so if the donor don't have one than oh well, Probably wont lighten the fly wheel to much part of its job is inertia, so it needs to be a little bit heavy or the saw can't overcome its own compression, as far as rods breaking, eh oh well If blown a few engines in my day taint that bad (famous last word right) only one way to find out if it works and that to do it.

I got a couple of dead jugs around here Maybe I can heat em up in the forge and time how long it takes to cool off before and after the drilling? (just can't get excited and leave em in there to long It sucks to clean the vent when bits of metal get welded to it)
 
I like the idea. They cross drill brake disks to improve cooling, so my guess is drilling the fins won't hurt and may help cooling. I once lightened a Triumph Bonneville by about 50 lbs, a significant part of which was removing extra metal from the reciprocating engine mass. It certainly increased the vibration.
Thats not why they drill rotors. The louvers in the middle of a high performance rotor are what extract 90% or better of the heat build up
 
I have a crazy Idea (like most of my ideas) I don't imagine I'm the first to think of this(like most of my ideas). Anyway chainsaws are heavy, I was think'n about getting another basket case saw get it runnin and then see just how much weight I could lose off from it.

The plan so far is to tear it down and see what every peice could afford to lose, smooth out casting lines, etc, Then drill a few dozen holes in the cooling fins say 1/4" dia, feather out some to the structural reinforcement type stuff (buttressss?), I kinda want to drill some larger holes in the connecting rod but not sure how that would effect flywheel balance or vibration... Maybe get real ambitious and thin the inner dia walls of the fly wheel (it would lighten it without affecting momentum to much)
The idea is to make a reliable saw that weighs a 1/2 pound or more less than its stock counterpart. I've toyed with porting and polishing my first time with this project, it would remove material while theoreticaly improving performance...

So anyway full time real machinist (as in I understand how and why of every machine type lathes mills cnc manuel etc) part time gypo logger, so I'm fat but still carry a saw three days a week, cutting metal is nothing new to me and dead reckoning i can figure whats minumum for structure, whats necesarry etc. the part that gets me is will drilling holes in the cooling fins affect their ability to cool the saw, and will drilling holes in the conecting rod make it vibrate out of my hand,
I could just put a light weight bar on it but I'm also a cheap bastard and those bars ain't cheap, so I was planning on trying to make my own. Out of a factory or a "junk" oregon bar(that should start some fights...) thanks for any help
I've done everything your talking about minus putting holes in the connecting rod because if your planning to make decent power gains it will most certainly fail. I have ground off material to lighten it with no issues at 18000rpm. As for the crank I took my knowledge of building race engines for motorcycles and gave it a knife edge but it dose need to be put on a balancer to rebalance otherwise at a certain point the rotational force of opposition will actually stop it from achieving its highest possible rpm plus its just a much smoother ride. Don't forget about the piston and pin. Lots of gains there if u know what to do. I probably wouldn't put to many holes in the flywheel as it could cause overheating issues. I just thin them out. It removes more material anyway. I could go on and on. But yea I'd like to know how it turned out.
 
G440 clone would be a good candidate. While you’re trimming everything put a 460 jug on and port it. Should pull 32” skip, no problem.
Tsumura lightweight bars can be found at reasonable prices.

If you don’t post pictures, it didn’t happen.
 
Oregon Versa-Cut bars are very light compared to standard bars. Mine is half a pound lighter than my standard bar in the same lenght (20inch). Plus they are only around $45-$55. A lightweight bar makes a big difference in how a saw feels, in my opinion.

Yes they aren't as durable being a laminated bar, but so far mine has impressed me.
 
Interesting thread. When OP mentioned drilling cylinder fins it brought a murky memory to the surface of same thing done to air-cooled motorcycles from the 1960's. IIRC, drilling a hole less than fin thickness will help cooling (and weight reduction) While going bigger(such as the 1/4" hole mentioned) will compromise cooling due to decreased surface area of the fin.
 
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