Possible Poulan 46 conversion...

[aubej]

Hey guys,
I've been thinking about maybe converting a Poulan 46 chainsaw engine for RC use. There is a good article at http://www.rcfaw.com.

I'm looking for advice from guys who have converted engines before. I think Kevin and Andrew have each done a few.

If I were to go with an electronic ignition, what would I need? Are there complete ignitions out there that I could buy?
Is it worth going with an electronic ignition? Would the weight saved from the engine be more than an ignition and batteries...
Is the electronic ignition used simply for ease of starting?

Looking forward to your responses.

Jason

[AJCoholic]

I have converted a few, staying with the stock magneto is possible and the main disadvatgaes are:

-reduced top end power due to a compromised low and high end ignition advance point

- same reason gives harder hand starting and rougher idle

- weight is usually more, allthough it depends as there are some lightweight flywheels and some use a monster battery pack for the electronic ignitions too.

I prefer (if money isnt a problem) to use a C&H synchrospark ignition. This is an auto advancing electronic ignition using a small hall effect sensor and a tiny magnet mounted onto something that rotates with the crank. It is set for the timing and then the computer automatically retards to a few degrees BTDC for easy hand starts and smooth idle, then as the RPM increases the computer automatically advances the timing to the preset point at full RPM, usually around 28 to 32 degrees BTDC.

Mounting the magnet is usually no issue as you can put it into the drive hub, and the bracket you make up to hold the hall effect sensor is also quite easy, even with just a drill and a file from nylon or something easy to work with.

The C&H setup costs roughly $225 Canadian direct from C&H including shipping and converting from US dollars, unless they have raised the price from last year.

I also had a Prospark ignition sold by Nelson Hobby but I didnt like it very much. I could not get the engine to run smoothly at all power ranges and it doesnt use a linear advance like the C&H but comes on strong after a few thousand RPM's. I like the C&H a lot better.

[aubej]

Thanks for the info Andrew. I think the CH ignition is the way to go. With it, I still think it's a decently priced engine.

Anybody have any leads on 46cc Poulans? I'm going to check out Princess Auto tonight...


Thanks,
Jason

[Kevin McGrath]

Im sure Andrew has done more conversions than I have but I agree with most of what he says.The big advantages using a CH unit on a conversion are weight since you lose the coil and flywheel and starting since the unit retards the timing for that purpose.Full advance is still about 28o BTDC so cant expect any big top end power increases.
Any particular reason you are looking at Poulan?What cc range are you interested in?What type of model and which specific one are you planning for the engine?Interested in other suggestions?

[aubej]

Just looking at the Poulan cause I read some good reviews. Any other suggestions for a reliable powerful conversion.
This will go on a scaled up Something Extra. The wingspan is 72", and cord is 16" for an area of 1152 in^2, so I think the 46 should be about right.

I'm open to suggestions as this would be my first conversion.

Thanks,
Jason

[Kevin McGrath]

I think the wing area and span you are indicating are a little small for for a 46cc gasser particularly if you are using a conversion which will normally be a little heavier than a made for purpose engine like ZDZ.Midwest for example make kits for a version of the EXTRA and CAP,for which they reccomend 45cc engines but the span on both is 80".
A lot of your engine decision will be tied up in the cost of the engine you buy to convert.realisticly you must compare that cost to a new ZDZ 40cc for example which comes with an electronic advance ignition and includes the battery and even an on off switch.Another potential bargain would be a good used Zenoah G38 or G45,for which C&H make bolt on electronic conversion kits including a new prop driver.Other possibiliies include staying with the size of plane you are looking at and going smaller on the engine,to a McCullogh,Ryobi,or homelite for example......all of which can be fitted with a custom C&H setup.
Bet you thought this decision was going to be easy,EH?
Incidentally that web site is "FAQ",not "FAW",and is one of the best sites around particularly for engine conversions.Reading about that Poulan got me interested ,and it looks like a winner to me,particularly with the flywheel trimmed back as in the pics,since it cant weigh much.
Why not talk nice to Andrew and see if he will chuck one in his lathe for you?Its childs play for a dude with his skills........
CH also make a plug in electronic unit at much less cost ,which is used to retard the timing for easy hand starting and then is removed that you may want to investigate.

[aubej]

Thanks for all the help Kevin. You're right, it's rcfaq.com....that's my fat fingered typo. :lol:
I was a bit hesitant about that size engine on a 72" span, but if you recall the Sig Something Extra, this is a scaled up version with a constant cord of 16 inches. The wing area would be just about exactly the same as the wing area on the Midwest 80" Extra, so I think it would make a good combo.

You're right, it's a lot of thinking. There are a lot of things to keep in mins when considering this type of conversion. I appreciate all of your help and will keep you posted.

Jason

[AJCoholic]

In regards to plane size, I am flying my AC-3D (giant profile similar to the something extra in layout) which is 16 pounds, 80" ws and 22" chord with a 40cc gasoline engine (dolmar head with C&H ignition) and it is a sweet combo.

Gas engines are a bit heavier and why not just scale it up to at least 80 or 85" wingspan? It will fly a lot better in the slower ranges since you have a lot lower wing loading.

Also, I would turn the flywheel for you, sure, if you tell me what you need done (it sounds like you are looking at some drawings?)

Kevin, I have 5 or 6 electronic engine conversions/installations so far, not a "pro" but have learned they are all pretty straight forward. I think for the money the C&H synchrospark is THE way to go :) Its allmost foolproof, as all you have to set is the initial sensor position, then its done forever.

When I was asking around for advice, everything I read/was told was to go with the C&H and I cant say anything bad about it yet. Just a bit pricey thats all..... but it is a one time purchase and you can even use it one more than one engine, a separate sensor/magnet (the only thing that is really stuck to the engine) is about $10 and you can simply unplug the ignition unit and transfer to a second engine/airframe quickly to fly more than one plane. Similar to swapping a receiver but with nothing to set up and only two plugs!

[Kevin McGrath]

Yes I agree on the CH unit.I have two at the moment one on a Ryobi conversion I did a while back.This is the third engine this particular unit has been on and it is easily switched from engine to engine.
There is a good market out there for converted weeders with the CH unit on it,or even just for the unit itself,so I always have the option of disposing of it and putting the $ into some new project......
I hate to see good equipment gathering dust rather than being used,or worse sitting and becoming obsolete,so I do a lot of trading and selling and buying particularly with engines.For example i just sold a nice 38cc Quadra to a lucky fellow in Sudbury and used the proceeds (plus a little!) to buy my first gas twin,an RCS(MOKI) 44cc,which will fill the hole left from the sale of the Quadra,on my Lazy Ace Bipe.This will be the seventh engine powering this particular model since I built it several years ago......

[AJCoholic]

So you got that twin! I remember reading about it and you asking questions without many answers on RCU a while back. It seems they deleted the twins forum as I cant find it anymore?!

[Kevin McGrath]

Yep I took the plunge and its a lovely piece of work too.I also bought a couple of Jim Bisson,s best for it, and they are his usual superb finish and fit.
Just waiting to get into our field and run it up on my test stand.lm going to write a review on it for RCC if Jason wants it.......
Looks like RCU buried the twin column in with gas engines ....that site is getting so huge it must be getting hard to manage....what an info bank though using their search feature!

[aubej]

I've been doing more reading, and it appears that the CH conversion kit for the 33 Poulan is a direct bolt-on for the 42. It's a bit pricy at about $190 US, but this still makes an engined that is cheaper than a ZDZ 40....which would be nice to have, but the price tag :shock:

Kevin,
I'd love to post your revue of the RCS 44 twin. New content is always a great thing.

Side question guys. When measuring your wing chord, do you include ailerons? My chord of 16" on this scaled up Something Extra didn't include ailerons. I'm guessing 3.5~4" ailerons.

Thanks again for the help guys.

Jason

[Kevin McGrath]

I have always assumed ailerons to be part of the surface of a wing on the basis that their area provides lift in neutral or deflected position.Any aerodynamic experts out there?

[JimMcIntyre]

Ailerons, flaps etc should be included, same for area impacted by fuselage, nacelles etc. The question gets more interesting with lifting stabs, oversized airfoiling of axles etc.. :?

[aubej]

Well, I went out and bought the engine today. REconditioned poulan 42cc. I'll take some pics as I start the conversion.

Jason

[AJCoholic]

Jason,
If you need some parts made up ask me first before you spend more $$....
I just "acquired" a 5 foot length of 3.5" diameter 6061-T6 aircraft aluminum yesterday :) - that should make a few mounts/crankcases/etc etc!! 8)


(I sent that gear today also)

[aubej]

Hi Andrew,
Thanks. I will do that. I'm going to check to see what is in that conversion kit that CH sells. I want to use their ignition system, so if it's worth it, I may order the complete conversion kit. I'll let you know....it's very much appreciated.

I started taking the saw apart, and am down to removing the clutch. Is there a special tool for removing the clutch? Any tricks? That thing is on there solid!

I appreciate the gear. Rob says thanks. Just got back home from a road trip, decals are going in the mail tomorrow.

Thanks again!

Jason

[aubej]

Here are some pics...

[AJCoholic]

One thing I do to any gas engine I build, is taske it totally apart and then stuff the cylinder with rags, and tape up the openings. Then I glass bead blast the exterior. Thats what gives the nice uniform matte look that all the manufacturers have. Its easy to do, and the smaller cabinets/gun combos are pretty cheap (about $225). Also, anywhere you cut away material, and file flashings, etc the bead blasting cleans it all up. Makes it look pretty darn professional!

[aubej]

Well, the engine is out. Not too bad I must say.
I have the CH ignition and prop hub on order. When I get it I will put the engine on a stand and run it up.
Looking forward to seeing what kind of numbers this little gas burner put out.

Jason

[Vulcan1]

I also have some questions on larger enginse. I modifyed a homy 45 from a chainsaw. I made a mount that some people think is nice loking.bolts on the fw(1/2in plywood) Turned the hub and shaft and made a pulley for staring. I. I don't like this setup(anywheres a rope i will get hung.
2. How do you start them on electric. I made a 2.5 to1 belt drive ratio on the starter,pulleys are nurrled for slipping and the motor does not have the jam to turn it over. It' just a whop whop and it is slow.
Iwould also like to trim some fin area, say down to the smaller base fins. Decrease weight and clean it up.
Plane is my own design like my q500 only bigger. It has an 81" x14.5" wing and the length 65" from nose to tail. Have had it running and has good idle with a bit of thump in the bottom end. There is a smooth transmission to high rpm but haven't measuered that. It also has no vibration passed mid transition. On the homade muffler it has a low pitch so it is nice to listen to.
If anybody could help I would change. Ch might come later but this seems to work fine once it is running
John :?:

[volksman]

the only way i got my cursed us engines to start is a rope on the shaft behind the prop usually one pull engine was not really used much till this summer cause it doesnt hand start very often slapping the prop i mesn slapping everything i can swing will start it every time but very hard on hand even with big glove and extra padding electronic is the way if ya can afford it rope is second choicea dynatron is an option but is expensive if ya already got starters. any one try the 14-24 v cordless drillsshould start up to a 62 but are they fast enough???????????

[Vulcan1]

Just tried my 18v cordless and it turns it over real good on high torque. Made my own cup for it so will fire it up on the weekend when there is help.
Thanks John :oops:

[Denmac]

Hi Jason. Just read about your problem clutch ?. I assisted in taking an chain saw apart just a few days ago. If memory serves me correctly, the clutch is held on by a nut, which has a LEFT HAND THREAD ? Try it.
Best of luck with your new engine. D.B.

[The_Big_H]

Jason:

I've worked on a few chainsaws, and yes, the clutch is on a left hand thread. Some use a nut, some the clutch is directly threaded onto the crankshaft.
Also..
Don Lowe (RCModeller magazine) suggests running conversions on glow/alcohol. I've tried it on an old beater weedeater - it screams. Throw away the coil AND flywheel, machine up an adapter to thread glow plug into sparkplug hole, and open up the mixture screws to get it rich enough (make sure your carb has both HI and LO speed mixture screws). Fuel too expensive? Go to local racetrack, find somebody running on alcohol. My local racer gets it about $1/liter. Still need to find local source for compatible oil - anybody know where I can buy Klotz Super Techniplate oil?

[Kevin McGrath]

See www.klotzlube.com
I bought a 12 pint case of their RC Lube recently and any >$50 order ships freght free at least in the continental US.
Worst case I guess is that they could tell you who carries their product in your area.

[volksman]

methyl hydrate will work also synthetic turbine oil used in gas turbine or jet engines works fine smells different castor sybthetic mix. my rossi 40 runs on the above mix with not much difference in performance. used turbine oil is cheap free if ya can get it

[Rosisco]

Hi I am new to this so please bear with me. I fly a Pouland 46cc gas engine. It is in a scratch built Sukhoi 82" bird that weight 17lbs. I purchased a pouland pro in the yellow case due to the fact that it has a chrome piston in it. I machined the flywheel and use the factory ignition. I also chose this engine due to the ignition is attached to the engine and no modification is required. The muffler and engine weigh about 5 lbs but it preforms well. I must note though that in an aerobatic aircraft you will not be happy with it unless you can get at least 8000 rpm an the ground. I started out with a 20x6 prop that turned at 7200rpm but it was not enough. It vertually stopped in the air on final if you idled down too far. It also seemed to lug in the air. I now use a 18x10 and am very happy with the speed, vertical and sound because I am sure that it is reaching at least 9000rpm up stairs. Don't be scared to let it wind out........this engine is used to cutting trees at 12,500rpm. The port timming is a little different.

[Rosisco]

sorry 20x8

[SpaceCowboy]

Hi Jason ; I have a Poulin chainsaw and i can't complain . It has run fine the last 2 years.

I was also eyeing up those engines at Princess Auto. :P

I did see at a flea market a Stihl concrete saw that had a 68cc ( i think ) engine in it. The price was cheaper than buying a Zenoah. Just a bit of work to cut it down for an aircraft.

[g-manz35]

I was looking at poulan 42cc chainsaws at Princess auto today and was flirting with the idea of a comversion. while reserching conversions on the net I was led back to this site. I was wondering how your conversion turned out and what the final weight of the engine was. I was looking at mounting it on a 4 star 1.20. I also was thinking of not putting an ei on it although all opinions seem to think its the way to go.

George

[Kevin McGrath]

I have had both EI and standard ignition 31cc Ryobi conversions in a 4/120 and I think the Poulan would be too heavy and too powerful for that model.

[g-manz35]

As I thought. I'm on a budget (my wifes budget) so I was aslo looking at some weed wackers. Ryobi the way to go? I assume if you buy some no name weed wacker the weight/conversion may not work very well.

George

[Vulcan1]

My Poulan 42 weighs 4 lbs. complete with ignition and muffler. All homemade. You should be around that weight with magneto ignition. As for power I think they call it a throttle. The part I like about the ignition is that it is easier to start. There is nothing wrong with magneto and if I was not alone 1/2 the time I would still be using it. :wink:
Not sure where in Sask. you are but Treecutter and Wingburner have them converted so you could pm them for help also. And if you need help I am also available.
John