Weedwacker Conversions - RC Groups
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Nov 06, 2017, 11:28 PM
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Discussion

Weedwacker Conversions


Is there a forum or sticky here that deals with conversion of weedwacker engines to aero use? I have a Poulan 46cc that I would like to convert but I need a carb, carb adapter, prop adapter and ignition system for it. I previously emailed with Ken Lambert but his site hasn't been updated since 2015 and my last message from him was in 2014.

All help appreciated,
Mark
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Nov 06, 2017, 11:40 PM
AMA 46133
Quote:
Originally Posted by mmattock
Is there a forum or sticky here that deals with conversion of weedwacker engines to aero use? I have a Poulan 46cc that I would like to convert but I need a carb, carb adapter, prop adapter and ignition system for it. I previously emailed with Ken Lambert but his site hasn't been updated since 2015 and my last message from him was in 2014.

All help appreciated,
Mark
By the time you finish you will have a heavy weedwacker engine that may or may not be compatible with the carburetor you put on it. Your money will be way better spent getting one of the more "modern" gasoline engine designed for RC aircraft use in the 50cc size.

If the Poulan is a well known engine that is reliable and durable maybe there is a reason to save it and compromise on the weight.
Nov 06, 2017, 11:47 PM
Registered User
Quote:
Originally Posted by SeismicCWave
If the Poulan is a well known engine that is reliable and durable maybe there is a reason to save it and compromise on the weight.
It was a popular conversion and works well. Ken offered kits to convert them but has dropped off the radar so I am looking for alternatives.


Mark
Nov 07, 2017, 12:04 AM
AMA 46133
Quote:
Originally Posted by mmattock
It was a popular conversion and works well. Ken offered kits to convert them but has dropped off the radar so I am looking for alternatives.


Mark
Sorry couldn't help you there.
Nov 07, 2017, 03:17 AM
UAS Pilot - FAA# *******HRK
CryHavoc's Avatar
The market for conversion parts hit the skids several years ago as soon as cheap gassers out of the orient flooded in. The reason people were converting in the first place was because of the limited and expensive market that existed for gas engines back then. Plus, guys like Ken were getting old even back then.

So unless you can make your own parts, you're probably out of luck finding anything commercial. I'm not saying nothing may be out there but they probably won't be cheap.

That being said, there is nothing wrong with conversion engines for guys like me that love to tinker and have machine tools to make my own parts. A lot of airplanes have been flown quite nicely with conversion engines so its not like they're useless. They're just not worth much these days. However, some of them can be just as light as hobby engines and besides, unless your into competition, you don't need the latest uber-light wunderkind engine.

Mike
Last edited by CryHavoc; Nov 07, 2017 at 03:25 AM.
Nov 07, 2017, 10:41 AM
Registered User
Quote:
Originally Posted by CryHavoc
The market for conversion parts hit the skids several years ago as soon as cheap gassers out of the orient flooded in. The reason people were converting in the first place was because of the limited and expensive market that existed for gas engines back then. Plus, guys like Ken were getting old even back then.

So unless you can make your own parts, you're probably out of luck finding anything commercial. I'm not saying nothing may be out there but they probably won't be cheap.

That being said, there is nothing wrong with conversion engines for guys like me that love to tinker and have machine tools to make my own parts. A lot of airplanes have been flown quite nicely with conversion engines so its not like they're useless. They're just not worth much these days. However, some of them can be just as light as hobby engines and besides, unless your into competition, you don't need the latest uber-light wunderkind engine.

Mike
Thanks, Mike. I agree on the conversion engines being decent for a lot of uses. I would use the Poulan on something like a Taylorcraft or Monocoupe where you need some weight to balance and balls-out performance isn't required. I guess I will have to design my own parts and see about getting them made locally by a couple of machinist acquaintances.

Where do I source a Walbro (or clone) carb that is suitable these days?


Thanks,
Mark
Nov 07, 2017, 11:44 AM
Registered User
Mark, here's a link to an engine conversion forum thread that might be helpful.

http://www.rcuniverse.com/forum/sear...earchid=384475
Nov 07, 2017, 02:14 PM
Registered User
Quote:
Originally Posted by Lowkey
Mark, here's a link to an engine conversion forum thread that might be helpful.

http://www.rcuniverse.com/forum/sear...earchid=384475
Thanks. I used to frequent RCU but the conversions forum has been really quiet for years now. That is where I first found Ken Lambert and his parts. FWIW, that link didn't work for me. This is the one I get when I log in to RCU:

http://www.rcuniverse.com/forum/engine-conversions-92/


Mark
Nov 07, 2017, 08:32 PM
Registered User
I keep picking weedwackers up at garage sales whenever I see them for $5 even if they don't work, in case I need a carb or whatever. I was going to make a couple RC boats. Never finished one yet, but started two They don't need any adaptors. The prop driver would be easy to make, The carb adaptor? maybe . IDK about the ignition, but there is a long thread about gas/glow adaptors. There is a spark plug thread to glow plug thread adaptor for $10 or $20 that you screw in and take off the whole magneto system. They run 1/3 glow fuel and 2/3 gas with 2 stroke oil. It was a popular thread for a while and then it fizzled out too.
Nov 07, 2017, 09:31 PM
Registered User
Quote:
Originally Posted by aspeed
The prop driver would be easy to make, The carb adaptor? maybe . IDK about the ignition, but there is a long thread about gas/glow adaptors.
Ken Lambert has pics of what he did on his site: http://www.lambertsrc.com/engines.html

The ignition is easy enough, RCExcel still make and sell them from what I can see. The hardest part is mounting the pick up and magnet. If I had a lathe and mill this would be no problem, but without machine tools I am stuck.


Mark
Nov 08, 2017, 06:29 AM
Registered User
Most converted engines use standard prop adapters that can be found as spare parts for other engines on sites such as hobbyking.
Over the years I have converted dozens of engines and have dozens more in different stages of conversion.
The following will fit many of the converted engines:
https://hobbyking.com/en_us/replacem...as-engine.html
Sometimes it's easy enough to cut out the prop adapter from the rotor/fan using a holesaw.
Other prop hubs are also readily available, I got a few RCGF and NGH prop hubs, they come with the magnets pre-installed and make a glow to gas conversion with EI a breeze.
I used the NGH 35 hub (12mm) for 2x OS FX160 and an ASP 180 two stroke, NGH 30 and NGH 38 hubs (10mm) fits nicely on my ASP 180FS's, Webra 120's and Moki135 amongst others.
Nov 08, 2017, 09:47 AM
Registered User
earlwb's Avatar
Years ago there used to be several small businesses with websites that sold conversion parts for gasoline utility engines. Unfortunately, the cheap gas engines coming out of China killed off the conversion market. It wound up cheaper to just buy an engine ready made instead of converting one.

Generally the trimmer engines are low power engines intended for their use in weed trimming. The engines do not develop a lot of power. The connecting rod is generally a stamped metal affair with needle bearings on it. So you need to be careful not to over-rev them.

But years ago everyone was converting gas engines over to use in model airplanes. The chainsaw engines tend to develop more power and fly the airplanes better. But you are forced to make a new crankcase for most of them.

When electronic ignition units became commonly available a number of guys machined the flywheel down into a prop hub spacer and put the timing magnet on it. Before then they kept the flywheel and used the magneto, but they would machine off the fan blades though.
Last edited by earlwb; Nov 08, 2017 at 09:53 AM. Reason: add more information
Nov 08, 2017, 02:57 PM
Registered User
Quote:
Originally Posted by ClippedWings
Most converted engines use standard prop adapters that can be found as spare parts for other engines on sites such as hobbyking.
Thanks, I will take a look at those. The engine is bare, with no cooling fan or carb on it so I will need to work from scratch.

Quote:
Originally Posted by earlwb
The chainsaw engines tend to develop more power and fly the airplanes better. But you are forced to make a new crankcase for most of them.
While I titled the thread with weedwacker, the Poulan 46cc engine I have is actually a chainsaw motor. It was the basis for the Brillelli 46GT motor if anyone remembers those. Fortunately, it used a beam mount set up so it is pretty easy to adapt it to mounting on a model.

Since the advice is flowing here, I might as well post a few pics of what I have:









The shorter, tapered shaft is the end that the prop goes on. The other end just gets cut off.

Just for reference, a couple shots of the Brillelli conversion:






Mark
Nov 08, 2017, 03:42 PM
Registered User
AA5BY's Avatar
I've recently participated on the RCU engine conversion thread and interacted there with av8tor1977 who is quite knowledgeable about conversions as are several here on RCG.

I've recently done a Ryobi conversion with EI, mostly because I had the engine and spare ignition and the Ryobi with rear carb and muffler fits well into the cowl of a planned build. And... it will meet the power requirements for the lazy floater.

If not having the engine or the ability to do the conversion myself... it wouldn't have happened.
Nov 08, 2017, 10:13 PM
Registered User
Your engine is similar to the McCulloch 42cc of which I have quite a few examples of.
It's a clam shell constructions which lets you change the orientation of the crankshaft easily.
You can choose where to fit the prop adaptor but may have to change the crankshaft's position internally and make sure that all other components stay where they are.
If I remember correctly, the opposite end (with straight shaft) is 10mm in width behind the threaded part, increasing to around 12mm. It should happily take one of the RCGF adapters, I think the 15cc and also 26cc, I will try measure, fit an adapter and report later tonight.


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