Dumb question.... Clamshell

[homemade]

I hear a lot of guys referring to clamshell motors. What are they? How are they different from a regular, split the case in half, type motor. The only experience I have with getting a chain saw down to that basic form is with a husky 281 and a solo 677.

 

[jughead500]

The clamshells split horizonally at the crankshaft centerline.the bottom have is sealed to the top cylinder portion and the whole assembly bolts into a plastic case.
The only dumb question is the one that isn't asked.

 

[fearofpavement]

A clamshell motor is a self contained engine that attaches into a plastic case. The cylinder has a pan on the bottom that looks a bit like half of a clam. The entire engine consists of the cylinder, crank, rod, piston, bearings and then the lower half (clamshell) hold that all together. They are more difficult to change cylinders on than other types but are no less reliable.

 

[Raganr]

This is what a clam shell looks like. To access the P/C/seals you need to pretty much take the entire saw apart.

 

[jughead500]

A clamshell motor is a self contained engine that attaches into a plastic case. The cylinder has a pan on the bottom that looks a bit like half of a clam. The entire engine consists of the cylinder, crank, rod, piston, bearings and then the lower half (clamshell) hold that all together. They are more difficult to change cylinders on than other types but are no less reliable.

Just a little less modifiable

 

[homemade]

Thanks guys.

 

[rjames]

UOTE="homemade, post: 5205518, member: 57572"]Thanks guys.[/QUOTE]
I believe your 460 is a clamshell saw. Ive cut a ton of wood with my 350 and its been extremely reliable. Never torn it apart, never had to.

 

[Raganr]

Just a little less modifiable

Is it just because you cannot cut the base of the jug/remove base gasket? What about a pop-up piston? Seems like other mods would work.

I know there are a few threads here about modifying clam shells. I need to go read them again.

 

[drf255]

A popup requires welding a dome on. I did it on an ms 250.

There's hugely varying opinions on whether or not the theoretical power increase from a popup's compression increase is mitigated by the adverse effects on flame travel.

 

[homemade]

UOTE="homemade, post: 5205518, member: 57572"]Thanks guys.

I believe your 460 is a clamshell saw. Ive cut a ton of wood with my 350 and its been extremely reliable. Never torn it apart, never had to.[/QUOTE]
I would love to look at my 460 but I no longer own it. It was stolen out of the back of my truck.

 

[Raganr]

I know it is a hot topic but for clam shells it's the only method to increase compression, right?

 

[Chris-PA]

Is it just because you cannot cut the base of the jug/remove base gasket? What about a pop-up piston? Seems like other mods would work.

I know there are a few threads here about modifying clam shells. I need to go read them again.

I'm working on the tooling for cutting a clamshell base right now. If that works then I'll see about moving the crank up in the cylinder. It does not look very hard actually, but we'll see.

 

[rjames]

Sorry about the bad luck chief. Hopefully the s.o.b gets what he deserves. Everything comes full circle eventually.

I believe your 460 is a clamshell saw. Ive cut a ton of wood with my 350 and its been extremely reliable. Never torn it apart, never had to.

I would love to look at my 460 but I no longer own it. It was stolen out of the back of my truck.[/QUOTE]

 

[Fubar]

i like them , clam shell designs lower production costs , weigh less and usually vibrate less , just harder to work on in some aspects.

 

[homemade]

I could see how it would be advantageous for the homeowner who wants a low cost and is going to be a low hour saw to be a clamshell. He won't be tearing into it when it started loosing compression. Doesn't want to have it vibrating his hands too sleep... All the features of a small homeowner saw produced as economically (cheaply) as possible.

 

[Jon1212]

This is from a while ago, and amongst the myriad of BS from Audible Fart, there is actually some good information.

http://www.arboristsite.com/community/threads/mastermind-meets-the-ms390.178738/

 

[DSS]

The boys did a wild thing build off a few years ago. I know Ed (Arrowhead) for sure rebored the main bearings in the case in his. Randy might have too.

 

[Jon1212]

The boys did a wild thing build off a few years ago. I know Ed (Arrowhead) for sure rebored the main bearings in the case in his. Randy might have too.

Is that Ed's 70cc Box Store Poulan?

 

[Jon1212]

Found It, but the Linkbucks fiasco killed the pictures.

I figured I'd knock the dust off this thread. Anybody still messing with the Wild Things? I made up a pipe for mine. I ended up with a 20% gain. In the video it's 10.5" wood, I'm running a stock chain.

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[DSS]

Is that Ed's 70cc Box Store Poulan?

No that was a 3300 maybe?, with an 038 mag top end. That was a cool build.