Theoretical custom case

[Rich Fife]

Like mentioned in some other threads... I tend to do *s-word the hard way... I don't like following the crowd and my comprehension lags... with that being said... crank swaps into various cases isn't the most fun thing to do... takes a bit of time and I'm the type that wants to see results sooner rather than later. So, in short... builds that drag out I tend to lose interest. Now, with that said... I have conflicted thoughts/ideas... the cats out of the bag about modifying a perfectly good 462 case and a perfectly good 461 crank... I love the weight savings of the 462s but I also like the power of the 461s... I figured combine the two and get the best of both worlds... I'm not sure it'll work as I hope or Intend it to, but, time will tell.

Anyway, I'm currently designing a custom case, modeled after Stihls design(s)... my end goal is to be able to swap different cranks... to either de-stroke or make it a stroker. I figured "how hard can it be... right?" .... Yeah, it's a pain in the ass with A LOT of measurements coming from the centerline(s)... but at the same time, it doesnt have my full attention as iI'm uilding and testing saws and in-between that I'm messing with the 461/462 hybrid... here are my thoughts for this case... the various strokes, widths and clearances have to be accounted for... so my thought process was to make precision bearings/seal adapters (some internal, others external) to compensate for the difference in crank widths, for the crank clearance... I'd machine insertable radius deflectors... for the cylinders different heights, I'd have pinned and possibly o-ringed cylinder spacers that can be added or removed to compensate...
I have yet to think about the side covers as well as the flywheel/clutch situation...

Coming from the racing scene... we are constantly stroking or de-stroking our motors... I feel it would be awesome to have a chainsaw thats 67cc one day and the next day using the same case 100+cc.
 

 

[jacob j.]

It can be done, depending on how much work a person wants to do.

A guy in Northern California designed and built his own crankcases for the Dolmar 166 - they were some trick-looking pieces.

One of the cases he set up to use (I believe) an 090 crank.

 

[Red97]

Sweet idea! But why not just make a crankshaft?

Profile the ends to match desired flywheel/clutch.

but it would be sweet to see custom case.

 

[Ketchup]

I feel like chainsaws never have a good place for things like reeds, power valves or turbochargers. It would be nice to see a platform that incorporated that stuff. Even just a crank with adjustable stroke and removable con rod(s) would be pretty sweet. Maybe then you wouldn’t need all the different bearing oddities. Something that wouldn’t require press or interference fitting. Just bolt and go.

Sorry, brain dump.

 

[wcorey]

Sounds like a fun rabbit hole.
Not enough pertinent details to give more than generalized opinions...
Manual machining or cnc? Sandcast or billet? TIG welder? Test bed only or intended for end use?

If I were going to spend that much time on such a project, simplicity and modularity would be first priority.
Build it like a bike saw, bare basic crank case with lots of material left on for plenty of attachment points.
Assuming no cnc, using billet, no effort on weight reduction. Just a basic rectangle block, can do the fancy time consuming stuff on version two or three.
In my own experience, in spite of the best laid plans, there will be a version two, three, etc., the first one eventually becomes shop art/sculpture, lol...
Don't bother with covers on version one, use a basic rope/pulley for starting.
Your plan to use seal/bearing, cylinder adaptors is a wise one, making as many features as modular as is reasonable is what's worth spending extra time on.

 

[Red97]

Can also find a case thst can fit lots of cranks/cylinders



This should be able to go from 38-96cc

 

[Rich Fife]

Sweet idea! But why not just make a crankshaft?

Profile the ends to match desired flywheel/clutch.

but it would be sweet to see custom case.

Machining a custom crankshaft and using various rods would be the smartest and easiest way to go about it, no doubt about it... but, it would be cool to build a saw mostly from raw materials. Like mentioned, I tend to do *s-word the hard way...
I do like the idea of machining a crank though!

 

[Rich Fife]

I feel like chainsaws never have a good place for things like reeds, power valves or turbochargers. It would be nice to see a platform that incorporated that stuff. Even just a crank with adjustable stroke and removable con rod(s) would be pretty sweet. Maybe then you wouldn’t need all the different bearing oddities. Something that wouldn’t require press or interference fitting. Just bolt and go.

Sorry, brain dump.

That's part of my thought process as well... ive been taking notes from my Pioneer 3270 Super and a few stihls... the pioneer has a 2 piece rod and Reed valves... personally, I love Reed saws... kinda like an old mechanical 850cfm quadrajunk carb that came off of a marine motor from the late 60's... it'll only pull what the motor desires.
I'm wondering how the rods would hold up to 17k rpms... if the rod/cap had recessed alignment pins built into them with some stronger bolts I'm sure it would work...
Well, now I have more things to ponder...

 

[Rich Fife]

Can also find a case thst can fit lots of cranks/cylinders

View attachment 370824

This should be able to go from 38-96cc

I thought about doing some things to a few 372 husky cases. I have a 2083 and a 2186 crank. The problem with those, the width and shaft diameters vs the cases width and bearing pockets depth and thickness... or lack of... I should check the hardness of those crankshafts... I should be able to turn them.

 

[Rich Fife]

Sounds like a fun rabbit hole.

Thats what I said... and then I went in, tip toeing.

Not enough pertinent details to give more than generalized opinions...

Opinions are welcomed, might spur some ideas.

Manual machining or cnc? Sandcast or billet? TIG welder? Test bed only or intended for end use?

I'll bounce back and forth from manual to cnc, it all depends on the operation at hand. Machine Work on the case will be cnc (g&m code)
If it works out, the thought process is to have some casted (if its not too expensive, as the ol' lady might kill me in my sleep)...

Material would be billet aluminum.
Yes I have both mig and tig capabilities.

If I were going to spend that much time on such a project, simplicity and modularity would be first priority.

Agreed.

Build it like a bike saw, bare basic crank case with lots of material left on for plenty of attachment points.

I really like this idea!!! And thays very similar to how my Pioneer was made.

Assuming no cnc, using billet, no effort on weight reduction. Just a basic rectangle block, can do the fancy time consuming stuff on version two or three.
In my own experience, in spite of the best laid plans, there will be a version two, three, etc., the first one eventually becomes shop art/sculpture, lol...

Always happens... I always look for things to change, to refine, etc...

Don't bother with covers on version one, use a basic rope/pulley for starting.
Your plan to use seal/bearing, cylinder adaptors is a wise one, making as many features as modular as is reasonable is what's worth spending extra time on.

Yessir!
I also like the idea on not wasting time on the covers until I get so.ething proved out/functional.

I definitely appreciate your input man! You kinda helped organize my thoughts...

Thank You.

 

[Rich Fife]

It can be done, depending on how much work a person wants to do.

In reality I want to do the least amount of work to get a finished product... but, something like this is 100% going to take time and a lot of planning...

A guy in Northern California designed and built his own crankcases for the Dolmar 166 - they were some trick-looking pieces.

One of the cases he set up to use (I believe) an 090 crank.

That would be awesome to see.

 

[wcorey]

If you can find the time, what with catching up on the universe of info buried here and other saw sites...
You should follow some of the crazy builds (strokers/bigbores shoehorned into smaller platforms) Red97 has done and documented both on the forums and 'tube.
He's of a relatively small percentage of people doing this sort of stuff that concludes with actual great running saws.
And then there's his dyno setup...

 

[Rich Fife]

If you can find the time, what with catching up on the universe of info buried here and other saw sites...
You should follow some of the crazy builds (strokers/bigbores shoehorned into smaller platforms) Red97 has done and documented both on the forums and 'tube.
He's of a relatively small percentage of people doing this sort of stuff that concludes with actual great running saws.
And then there's his dyno setup...

DynoJoe?

 

[East/West CADaddict]

DynoJoe?

Yeah, that's his handle on here Red97

 

[wcorey]

DynoJoe?

Yeah, he may be one of the 2-3 guys on here who know their chit.

Sorry..., gonna be a while before you live that one down...

 

[Ketchup]

It’s worth your time to check out Twostroke Stuffing on YouTube. Not chainsaws, but he’s built several ground up theoretical engines for bikes and documented it well. It’s a lot of content though and not all of it is engine related.

 

[BarkersSaws]

Sweet idea! But why not just make a crankshaft?

Profile the ends to match desired flywheel/clutch.

but it would be sweet to see custom case.

He’s gonna make me get out some pics of my uncles work.

 

[Rich Fife]

It’s worth your time to check out Twostroke Stuffing on YouTube. Not chainsaws, but he’s built several ground up theoretical engines for bikes and documented it well. It’s a lot of content though and not all of it is engine related.

I watch him. He's next level smart.

 

[Rich Fife]

Can also find a case thst can fit lots of cranks/cylinders

View attachment 370824

This should be able to go from 38-96cc

Joe, is that a 2 series Husky case? What cranks can you fit into that specific case With the different shafts diameters and counter weight widths?

 

[Red97]

Joe, is that a 2 series Husky case? What cranks can you fit into that specific case With the different shafts diameters and counter weight widths?

That is an echo case.

Stock is 32mm stroke. The generation prior is 34,36mm and the generation after has 37.6mm.

Bearings and seal diameter are good, widths are the same or less. And plenty of shaft to make the flywheels/clutch tapers/threads.

Some hard turning is involved, but it's doable.