OT-Dumb idea, homemade con rod?

[JohnL]

It's not for a saw, but a cheap 2 cycle blower I want to up the power on. I suspect the bottom end will be the weak link. If I were to try to make my own heavier duty connecting rod, what are the issues with weight and ballance, how will it change the overall ballance using the stock crank counterweights-. THe unit is a POS, and I'm not too worried about breaking it. But If I can do it right and learn something that would be fun. Just throwing it out there if anyone knows what kind of design considerations need to be taken into account.

 

[Lakeside53]

"heavier duty" would be more about heat treatment and other conditioning, than bulk...

First the right alloy, then "forging" (if that's the route to be taken), then precison machining of both bearng ends... and finally heat treatment.

Oh.. a cheap blower usualy has a pressed crank, so you'll need to press it all apart (and realign) it to put on your own rod.


And when you've finished, it will run no better then the orginal:greenchainsaw:



'Bottom end" is more than rod - it's the entire crank, bearings and case....

 

[JohnL]

First stage I want to adapt an adjustable carb to fit it, open up the muffler.

Second, remove base gasket, raise exhaust port roof by gasket thickness.

Third stage, try cleaning up the ports without going overboard.


I know it's kind of pointless, more for fun.

 

[stihl only]

Can you spend that time earning overtime at work? Then you could just buy a BR600 and be done with it!!

What would be an easier experiment would be to see how far you can mod it before the stock rod fails. I'm betting it never will!

 

[Lakeside53]

I bet Brad could bend it:greenchainsaw:

 

[stihl only]

OUCH!! Talk about kicking him when he is down!

 

[JohnL]

Can you spend that time earning overtime at work? Then you could just buy a BR600 and be done with it!!

What would be an easier experiment would be to see how far you can mod it before the stock rod fails. I'm betting it never will!

If it blows up I'll post some pictures


It already sounds like something is rattling in the case, probably less than 10 hours total run time on it.

 

[blsnelling]

I bet Brad could bend it:greenchainsaw:

Only if he does like Stihl and builds it so weak that you can't even disassemble the engine using conventional methods.:greenchainsaw:

 

[Gumnuts]

LOL...yes pics with footnotes would be good.

 

[Fastcast]

Only if he does like Stihl and builds it so weak that you can't even disassemble the engine using conventional methods.:greenchainsaw:

OUCH!

 

[Lakeside53]

It's a case of big muscles and small.... never mind.... opcorn:

 

[blsnelling]

LOL. The sad thing is that the scrench was stronger than the conrod! It wasn't bending.

 

[Jredsjeep]

i vote to do it, why not, it think it would be fun and would give it a try if i had the equipment.

 

[mtfallsmikey]

Why not!...WTH, I love science projects!

Mine: go-cart with a toilet mounted on it.

 

[JohnL]

The Victim

Pics of the victim.


The rectangular block of material is the catalyst, it sits right against the exhaust port from the cylinder, looks pretty restictive. It's a few feet of wire coated with catalyst ( I assume?), stuffed into a rectangular well, and it lifts right out. The exhaust screen has plenty of surface area, I have no reason to remove it. The outlet tube looks to be about 30-40% of the area of the exhaust port, so adding another one may be in order. I have an adjustable walbro WT carb on order, will need to make it fit.

 

[romeo]

A homade connecting rod is a bad idea, I HAVE PROOF.....

 

[chowdozer]

Make one out of Ti. I have a 440 rod sitting here I've been looking at for 6 months. If you make one, make it longer. You'll have to run a spacer under the cylinder.