Where to get crank & piston balanced

[ArthurKnowles]

I have a new Predator Carbon SE gasser on order from Rick's. It has the 231PUH motor in it. I hear a lot about vibration on these gas motors and was thinking it might be worth it to have the crank & piston balanced before running the motor.

The questions I have are:

1) Is it worth it? Meaning, will it help eleminate vibration. Will it help the longevity of the airframe and electronics?

2) Who should I have perform this service? A local shop? I'm sure I could find small motor repair shops, or performance shops, in the area that could do the job. It's just a matter of looking. I'm just wondering if I should look at small motor boar racers or others with hands on experiance to do the job.

Thought? Suggestions?

Art

[CustomPC]

Gassers, by their very nature of being a large single cylinder engine will always vibrate a little.

The 231PUH is very good with only minimal vibration.

The 260PUH in stock form is a shaker and many of the modded engines from the shops like Hansens etc lighten the piston to approx the same weight as the 231 piston which substantially reduce the vibes.

[ArthurKnowles]

Ah, that's intersting. What about the flywheel? Any need/reason to balance it any more than the stock configuration?

[rbort]

The 231 had the right piston to crank weight. You should pull out the flywheel and balance that (its not balanced stock) by drilling dimples on the back side where its heavy.

The G26 is a G231 with a bigger piston and head bore. The crank is the came as the 231. Due to this, you need to lighten the piston (g26) in order to match the weight of the G231 piston so that it doesn't shake. Al at Hanson's does an excellent job at this. Also of course you need to balance the flywheel, and while Al has it he also checks and trues the crankshaft reducing it from as much at 2 thousands off (zenoah within tolerances) to less than 1/2 a thousands off.

-=>Raja.

[Gyan]

Also to add to Raja's post, the crankshaft also has material removed from the connecting rod side, to further the weight discrepancy of the heavier piston. Al at BH Hanson is the guy to do it.

[PaulH]

How much does Hanson charge for balancing and modding?

[Gyan]

It varies depending on what is found during the process. Mine ended up costing $185 cause I needed new crankcases & brgs, I think around $120 is the price, Why ask here when you can ask Al ??

[PaulH]

'caus it's 2200 and I doubt that he's taking phone calls this late on a Friday preceding a holiday weekend.

[rbort]

'caus it's 2200 and I doubt that he's taking phone calls this late on a Friday preceding a holiday weekend.

Paul I sent mine it cost me $140 cause I didn't need the crankcase I guess. I also got bearings plus the rest of the works.

-=>Raja.

[PaulH]

Okay, so I should figure on $150-$200, depending on how much TLC it needs. My 26 is starting to act up again. I think I have an air leak around the insulator block again. I figure that if I'm going to pull the engine, I may as well send it down to Hanson to get it balanced, then put a Z-RC insulator block on it. I know the Intrepids work just fine with a stock 26, but what the heck. :glasses2:

[rbort]

My theory is, if it can made to vibrate less, then do it. Works or doesn't work, (kinda like my 1005 vs the Spectra), in the long run a less vibrant motor makes for a longer like on the machine and electronics.

-=>Raja.

[Gyan]

I can't really say the Intrepids would work fine with a stock G26. I don't think any aircraft can. I know some claim this but if ANY engine is out of balance your going to have issues. My engine was way off in my Intrepid, it wore bolt holes bigger in the frames, cracked exhaust headers, broke bolts, cracked engine cases, shall I go on???? By the way this engine was purchased at Hanson's new and was described as a G26 Pro, I've since sent it back and did the plus mod (at $185.00) It's still vibrating too much for my liking but it may be the needles & it has to be broken in yet.

[PaulH]

Raja: Agreed, but I haven't had any significant problems with mine. Nothing vibrates much once the needles are set correctly and my head speed is up.

Gyan: This is called the fallacy of Hasty Generalization (http://onegoodmove.org/fallacy/hasty.htm).

Bergen has hundreds of these units in the field. Many use the airplane version in models with a 70-80" wing with very good results. Most people don't have a problem with it. I'm sorry to hear that you had issues with yours, but the vast majority of the G26 engines seem to work fine.

[rbort]

Raja: Agreed, but I haven't had any significant problems with mine. Nothing vibrates much once the needles are set correctly and my head speed is up.

Gyan: This is called the fallacy of Hasty Generalization (http://onegoodmove.org/fallacy/hasty.htm).

Bergen has hundreds of these units in the field. Many use the airplane version in models with a 70-80" wing with very good results. Most people don't have a problem with it. I'm sorry to hear that you had issues with yours, but the vast majority of the G26 engines seem to work fine.

Paul:

I think what you are saying is that your Bergen can tolerate it (the vibrations). That statement also depends on how often you fly and how much you fly. Its a known fact that a G26 is nothing more than a G231 with a bigger piston on top. But the G231 was built with a piston weight that matched the crankshaft counterbalance and connecting rod weight. If you put a bigger piston up top which is heavier, then the engine is going to shake no question about it. What I was saying is by having someone reduce the piston weight all the way down to the same weight as the G231 if possible will restore the original vibration levels from the G231 or close to it. Why not do that is my question?

Lets put it this way. I've logged over 1600 flights or 400 hours with gassers in the air since 1997. Years back, around 1998 or so, I decided to get my engine balanced at Hansons. I did it for the smoothness and not the power. I wanted to reduce vibrations as much as possible as I fly alot and I want things to last as long as possible. I tell you back then my fins used to buzz. I got the Hanson motor and put that in and no other changes and the fins stopped buzzing. That alone was the best thing that I did for the machine, and the # of flights prove it. I didn't care about the extra power at the time, but it sure was a bonus. Smooth is key.

I understand you say it works and people do it. What I'm trying to say is take two engines and two helie, all brand new. Balance one and not the other. Put all new electronics in both. Fly both one smooth and one shakier and see over time which one lives a better life and which one lasts longer from the electronics to the airframe.

I'm willing to bet that the smoother one will be the one. That being said, why wouldn't you invest $140 for example to smoothen out your engine (peanuts in comparison) if you can. When things last longer, it will pay for itself in no time.

By the way, you and I need to meet. You are in MA and so am I. Maybe even we already met, but I just know you as the Paul from MA with Bergens. Are you going to the FF in Keene NH on the 15th of July? If so let's meet up there. Would be nice to put a face to the name online :D

-=>Raja.

[PaulH]

Raja,

I do agree with you on the smoothness thing. Believe me, I understand exactly what you're saying. I probably will send my engine out at some point, but there are a few other financial commitments that I have to deal with first.

We did actually meet, briefly, at the Ernie Huber in 2005. Being a bit of a geek myself, I was bugging you for details on your generator's electronics. :) We'll catch up again sometime this summer. The Looper's field is about an hour from my house. I belong to the 107th in Revere (about 1/2 hour from home).

This is the first I have heard about the FF in Keene. My folks are coming out to visit that weekend. That's not something I should reschedule, if you know what I mean. :arggg: