Homemade Reduced Weight Bar

[SOS Ridgerider]

Pre-preg?

I'm going to draw a bar up in solid works and make some cuts in it. I can set the material to chromoly and check compressive force along with several other forces.

SOS, if you cut another bar I can tell you to avoid the square corners if possible. Even just a 1" corner radius would be better. I can explain more later, but I think you know what I'm getting at.

What I have here is what's used on school buses to bond the body sheets together, without the need for rivets. It's a Henkel product, and is what the engineers at Henkel recommended using. I just don't have the mixing gun for it on hand. I can borrow one from them, but I need to have the bar cut out and ready first.

The bars are about 5mm thick, so my idea was to have 2mm milled down from each side for the rim edge around the cutout. I was going to use 1.5mm or 2mm carbon and bond those in place, minimizing the amount of bonding agent and maximizing the amount of carbon used. I was forced to use 1mm carbon instead, as the cutout and rim edge wasn't perfect, and had slight variations in depth. Having the inserts flush with the rest of the bar was my main goal.

If you look back to the start of the first bar I did, you'll see the edges I had drawn were way more rounded than they ended up like. I was limited to what my buddy could do, and beggars can't be choosers.

 

[mettee]

.......

 

[mettee]

Center rib is cut to .040 in this render, all dimensions are adjustable on the fly for bar length.

 

[RedGas]

Does anybody just make a carbon-fiber bar with steel rails? Seems like that's the way to do it. CF with resin should be plenty strong/stiff.

All you need steel for is the wear factor of the chain running around it. 1/4" height should be enough, seems like. And some steel at the tip for the rivets for the sprocket tip to go through.

I'm thinking a 3/32" or 1/8" thick piece of styrofoam or balsa or something that weighs nothing, with layers of CF impregnated with resin around it to form a torsion box, vacuum bagged, with a band or rail of steel as an enclosure...I don't think it would be very hard to make.

If this has been discussed already, pls ignore, as I haven't read the entire thread yet.

 

[Willard]

Just found this thread , quite a read.
I built a lightweight bar 34 years ago and still holding out strong today on my 40 h.p. bikesaw.

Built it by accident and kinda wish I never did. Summer of 1984 I stopped in at General Bar Co. in Tigard, Oregon and had them build me a 3002 mount 17" salmon belly bar with 2 7/8" roller nose.
I supplied the roller nose and they built the bar for $50
Beautifully done polished like chrome and only 0.160" thick with .050 kerf.

I get home and ran it on my freshly built YZ bikesaw then got a brain wave from looking at old McCulloch saw pics with holes in their bars.

Took it to my machinist for him to cut 4 holes in it. He thought I was crazy ruining this beautiful hand made bar. But went ahead.

Tested it in couple year old dry timbers and the YZ cut good with it.
But at the first competition in green frozen spruce the bar jammed up solid with chips in the second cut.

Back to the drawing board I ended up installing aluminum cutouts and a coating of JB Weld on both sides.
Almost 35 years today the JB Weld is still holding strong and still stiff as ever. Pics show 72LG practice chain on the bar.
Last pic shows it weighs 2 1/2 lbs

 

[Rob Stafari]

This has been on my radar for a while. I have a friend who makes custom carbon fiber car parts for exotic cars. I am his resident house/dealership/shop remodeler. I've worked a deal with him and am slated to get some CF shop/class time learning how to mold and make top covers for my Dolkitas. After that I should have the base knowledge to start tackling the reduced weight bar with a little help from his shop and tools.

 

[Willard]

Here's a better pic of it on the scale.
Yup 2 1/2 lbs and 35 years old.

 

[Willard]

42mm carb on a 36 year old YZ125 bikesaw

 

[RI Chevy]

Really cool Willard!

 

[Willard]

Really cool Willard!

I got a 250 bikesaw in the planning stages but still have plans for this 125.
The 125 in its history went through 2 design changes, last one in 1988.
Going to reverse its engine rotation and make it right hand drive. Plus get it down close to the weight of a 3120XP.
Will look at a alky nitro setup on it.

 

[RI Chevy]

Whew! Awesome.

 

[CR888]

You were ahead of your day filling in cut outs on a solid bar Willard some 35 years ago. But like myself who tried it a year or two ago you soon realise hollow holes don't work consistently well in all wood types/conditions. I have a Cannon fatbelly 25" roller nose hotsaw bar that is a prime candidate for some machine work, they get damn heavy at that size. I'm surprised Cannon don't offer reduced weight options for their custom race bars.

 

[Willard]

You were ahead of your day filling in cut outs on a solid bar Willard some 35 years ago. But like myself who tried it a year or two ago you soon realise hollow holes don't work consistently well in all wood types/conditions. I have a Cannon fatbelly 25" roller nose hotsaw bar that is a prime candidate for some machine work, they get damn heavy at that size. I'm surprised Cannon don't offer reduced weight options for their custom race bars.

CR888, I bought my first special order race bar from Cannon 40 years ago in the first 2 pics below.

The trick with competition bars is to have it made as thin as possible for allowing those up to 40 hours to make race chains to cut.
A standard bar is any wheres from 0.180" to 0.200" thick, this 16" .050 bar Cannon made me in 1978 is 0.138" thick and weighs 1 lb. 14oz.

My 28" Cannon .063 hotsaw bar is 0.162" thick and 5 lbs 4 oz.
So custom race bars are considered weigh reduced with their thin profile.

Last 2 pics is my 20" Stihl Light bar at 2 lbs 1oz and a thick 0.186.5"

 

[Willard]

 

[Willard]

So just to annoy everyone just a bit more
Here's the thickness of my General 17" .050 lightweight fat belly bar. Exact same thickness as my Cannon 28" .063 fat belly solid bar.
Kudos to Cannon as I told them to make the 28" the exact same thickness as the older General. That they did.

Both bars are .024" thinner then my Stihl 20" Light bar.

 

[Willard]

One more
My 1978 Cannon 16" lightweight Cannon bar at 1 lb.14oz and 0.138.5" thick is .048" thinner then the Stihl Light.
And from my "feel test" in the bench vise just as stiff.

 

[mettee]

I'm going to do my cut out on a 26" cannon bar. I'll do a one piece insert that contains a blend of spectra and spread tow carbon. I am going to use a run of the mil resin thats good to 200 f. That will be a good long term test bed.

I can also do a dxf file for anyone who wants to machine there own own bar, any custom layout you want. I have a good pattern for strength, I ran it in solid works and it appears to respond well. I can add length or shorten as necessary. I kinda feel like 36" bars are the break point. No sense in trying to go light on longer bars.

 

[hseII]

I see this thread has been resurrected. Nice!

I have used both of my carbon bars a little bit by now, and they do just fine. I’ve had a few inquiries if I can make them for other people too, so I’m looking for someone with a mill, who can help me out with cutting them.

In all honesty, the stiffness of the bar depends a little on what bar you start out with.

The 32” GB bar I got from @Jon1212 was quite a bit stiffer, and nicer quality, than the cheap Laser bar I used for the 36” project. I never got around to doing the stiffness tests, but it’s clear that the Laser bar is more whippy than the GB.

Going forward, if I can make more, I’ll probably start with Oregon PowerMatch bars. They are consistent quality, tried and true, and available anywhere.

I’m sure there are many ways to make them better than what I’ve done, but they’re working very well for a hack like me. I haven’t used either of the 32”-36” for felling yet, so it’s all been bucking cuts and play, and the flex doesn’t bother me. My RW Oregon 34” bar isn’t any less whippy, for that matter.

Jon’s idea was to make a true homemade reduced weight bar, which he did a great job with. I took it one step further, and incorporated a few tools that most people don’t have in their homes, although my buddy does. Lol

It would be cool to see someone take this further, and really engineer it, even though at that point we’re getting further and further away from homemade.

I see the last posts address the concern about temperature, and the epoxy’s ability to handle it. In my experience there hasn’t been any issues with the epoxy. At all. I’ve done some long cuts with them, and many in a row. No sign of any stress or softening anywhere. The saw porters use the same epoxy I used, inside the jugs, to get the numbers where they want them. I have the feeling a jug gets at least as warm as a bar under operation. Lol

This is probably the longest post I’ve ever written. Good Lawd!!!

You don’t talk this much in 3 weeks Sonnie.


Sent from my iPhone using Jon1212 Pro

 

[SOS Ridgerider]

You don’t talk this much in 3 weeks Sonnie.


Sent from my iPhone using Jon1212 Pro

Lol. I’m a quiet guy. Usually there is more for me to learn by observing, rather than chiming in and confusing everyone.

 

[Adirondackstihl]

Lol. I’m a quiet guy. Usually there is more for me to learn by observing, rather than chiming in and confusing everyone.

Sup dood!