Weedeater, What do you think?
07-28-2005 | 03:52 PM
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Weedeater, What do you think?
Hello,
I reversed the cylinder on my Weedeater 25cc blower engine. This provides greater room for different mufflers and much better cooling for the hot side of the cylinder. It required trimming back the fins behind the coil and trimming the case coil support a little for the carb flange clearance. Also the center baffles in the crankcase transfer ports had to be removed. They no longer lined up with the cylinder transfer baffles. It weights 55oz. without the muffler.
Dave
I reversed the cylinder on my Weedeater 25cc blower engine. This provides greater room for different mufflers and much better cooling for the hot side of the cylinder. It required trimming back the fins behind the coil and trimming the case coil support a little for the carb flange clearance. Also the center baffles in the crankcase transfer ports had to be removed. They no longer lined up with the cylinder transfer baffles. It weights 55oz. without the muffler.
Dave
08-01-2005 | 07:31 AM
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From: dearborn,
MI
RE: Weedeater, What do you think?
Neat Job & Clever Idea! Congrats! What are you using for prop shaft spacer? Is prop mounted on orig crankshaft extension? Did you make your own mounting plate? I have a Sears/(Poulon?) 24 cc blower. The rear engine cover is a metal casting w/ 2 round lugs to engage rubber insulators to mount it to the plastic housing. Did you have plane your rear cover flat to fit your mounting plate? Thank you.
08-01-2005 | 12:06 PM
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From: Blairsville ,
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RE: Weedeater, What do you think?
Hi Dave,
Thats interesting what you did. I have worked on a couple of Weedeaters, but I haven't flown one, yet. One point I might question is about the piston ring pin. Did you keep the area of the piston and its ring pin running in the same area of the cylinder that it used originally? The area where it normally runs is wider than the other side. If you lifted the connecting rod from the crank pin and turned the whole assembly, it will all be in the same relationship as built by the factory. Another point I would ask you to consider is using the blower crankshaft the way you have it so far. I have one of these long crankshafts and I don't think I would trust the flatted end of the crankshaft to hold a prop on. I think it would be much better to cut the shaft and thread the end, but it has to be done on a lathe as you probably know, or just find another crankshaft from a Weedeater trimmer. I would be wary of using the long shafts to drive a prop for another reason, the prop is pretty far from the bearings, this amounts to a fairly long cantilever load on the bearings. The airplane when in flight has a spinning gyroscope in the form of a propeller and when you turn the airplane the gyroscopic load is considerable. Remember holding a child's gyroscope toy while it spins? you can feel the load when you move it around and what are they, 3" in diameter. This is long but it it also could be a safety issue. The bearings probably wouldn't last as long either.
I am converting two of the 25cc Toro engines you posted the photos on. I need to find a metric? tap to match the threads on the shaft to machine the prop hubs. The rest of the bolts are SAE! One of these engines has a two barrel carb and the other has a single barrel carb. I want to test run both of these soon. These Toro engines are high compression compared to some others and I wonder how smooth they are going to run after conversion. I ran them before I started to convert them. I suspect one of the reasons they are on the surplus market is: Did you notice how hard they are to crank with the cord? The pull cord system is a relatively small diameter and the compression is high, so they are hard to crank, but the quality of the engines and the machine work is also high. I'll post what the results are later.
Thats interesting what you did. I have worked on a couple of Weedeaters, but I haven't flown one, yet. One point I might question is about the piston ring pin. Did you keep the area of the piston and its ring pin running in the same area of the cylinder that it used originally? The area where it normally runs is wider than the other side. If you lifted the connecting rod from the crank pin and turned the whole assembly, it will all be in the same relationship as built by the factory. Another point I would ask you to consider is using the blower crankshaft the way you have it so far. I have one of these long crankshafts and I don't think I would trust the flatted end of the crankshaft to hold a prop on. I think it would be much better to cut the shaft and thread the end, but it has to be done on a lathe as you probably know, or just find another crankshaft from a Weedeater trimmer. I would be wary of using the long shafts to drive a prop for another reason, the prop is pretty far from the bearings, this amounts to a fairly long cantilever load on the bearings. The airplane when in flight has a spinning gyroscope in the form of a propeller and when you turn the airplane the gyroscopic load is considerable. Remember holding a child's gyroscope toy while it spins? you can feel the load when you move it around and what are they, 3" in diameter. This is long but it it also could be a safety issue. The bearings probably wouldn't last as long either.
I am converting two of the 25cc Toro engines you posted the photos on. I need to find a metric? tap to match the threads on the shaft to machine the prop hubs. The rest of the bolts are SAE! One of these engines has a two barrel carb and the other has a single barrel carb. I want to test run both of these soon. These Toro engines are high compression compared to some others and I wonder how smooth they are going to run after conversion. I ran them before I started to convert them. I suspect one of the reasons they are on the surplus market is: Did you notice how hard they are to crank with the cord? The pull cord system is a relatively small diameter and the compression is high, so they are hard to crank, but the quality of the engines and the machine work is also high. I'll post what the results are later.
08-01-2005 | 05:01 PM
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RE: Weedeater, What do you think?
ORIGINAL: rollmyown
Hi Dave,
Thats interesting what you did. I have worked on a couple of Weedeaters, but I haven't flown one, yet. One point I might question is about the piston ring pin. Did you keep the area of the piston and its ring pin running in the same area of the cylinder that it used originally? The area where it normally runs is wider than the other side. If you lifted the connecting rod from the crank pin and turned the whole assembly, it will all be in the same relationship as built by the factory. Another point I would ask you to consider is using the blower crankshaft the way you have it so far. I have one of these long crankshafts and I don't think I would trust the flatted end of the crankshaft to hold a prop on. I think it would be much better to cut the shaft and thread the end, but it has to be done on a lathe as you probably know, or just find another crankshaft from a Weedeater trimmer. I would be wary of using the long shafts to drive a prop for another reason, the prop is pretty far from the bearings, this amounts to a fairly long cantilever load on the bearings. The airplane when in flight has a spinning gyroscope in the form of a propeller and when you turn the airplane the gyroscopic load is considerable. Remember holding a child's gyroscope toy while it spins? you can feel the load when you move it around and what are they, 3" in diameter. This is long but it it also could be a safety issue. The bearings probably wouldn't last as long either.
I am converting two of the 25cc Toro engines you posted the photos on. I need to find a metric? tap to match the threads on the shaft to machine the prop hubs. The rest of the bolts are SAE! One of these engines has a two barrel carb and the other has a single barrel carb. I want to test run both of these soon. These Toro engines are high compression compared to some others and I wonder how smooth they are going to run after conversion. I ran them before I started to convert them. I suspect one of the reasons they are on the surplus market is: Did you notice how hard they are to crank with the cord? The pull cord system is a relatively small diameter and the compression is high, so they are hard to crank, but the quality of the engines and the machine work is also high. I'll post what the results are later.
Hi Dave,
Thats interesting what you did. I have worked on a couple of Weedeaters, but I haven't flown one, yet. One point I might question is about the piston ring pin. Did you keep the area of the piston and its ring pin running in the same area of the cylinder that it used originally? The area where it normally runs is wider than the other side. If you lifted the connecting rod from the crank pin and turned the whole assembly, it will all be in the same relationship as built by the factory. Another point I would ask you to consider is using the blower crankshaft the way you have it so far. I have one of these long crankshafts and I don't think I would trust the flatted end of the crankshaft to hold a prop on. I think it would be much better to cut the shaft and thread the end, but it has to be done on a lathe as you probably know, or just find another crankshaft from a Weedeater trimmer. I would be wary of using the long shafts to drive a prop for another reason, the prop is pretty far from the bearings, this amounts to a fairly long cantilever load on the bearings. The airplane when in flight has a spinning gyroscope in the form of a propeller and when you turn the airplane the gyroscopic load is considerable. Remember holding a child's gyroscope toy while it spins? you can feel the load when you move it around and what are they, 3" in diameter. This is long but it it also could be a safety issue. The bearings probably wouldn't last as long either.
I am converting two of the 25cc Toro engines you posted the photos on. I need to find a metric? tap to match the threads on the shaft to machine the prop hubs. The rest of the bolts are SAE! One of these engines has a two barrel carb and the other has a single barrel carb. I want to test run both of these soon. These Toro engines are high compression compared to some others and I wonder how smooth they are going to run after conversion. I ran them before I started to convert them. I suspect one of the reasons they are on the surplus market is: Did you notice how hard they are to crank with the cord? The pull cord system is a relatively small diameter and the compression is high, so they are hard to crank, but the quality of the engines and the machine work is also high. I'll post what the results are later.
The weed eater case and back plate had to be trimmed and filed flat for the mount. The mount is pretty simple. Go to your local recycling center and buy some scrape aluminum plate. I reduced the lenght of the shaft by about 5/8",but I could thread it and make it shorter. The pinned ring has been moved from the exhust side to the intake side where it Has more roomto run. It was very close to the exhust port stock and got worse when the exhust was widened. You don't have to flip the cylinder, it just makes more room for the muffler. I took the Toro flywheel nut to the hardware store today and determined the size of the stud. It is 8x1.00mm. The rear stud is 8x1.25mm. I am going to need a prop hub also. I checked the stock timing on the Toro and it is: Intake=60 degrees btdc, Exhust=65 degrees BBDC, Transfer=51 degrees BBDC. Teh intake is the same as the stock Homelite 25, but the exhust and transfers open a little late.
Dave
08-02-2005 | 10:00 AM
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From: Blairsville ,
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RE: Weedeater, What do you think?
Hi Dave, I use aluminum plate to make rear mounts also. Since you mentioned mounts, I try to keep the mounting plate at 3"x4" with the firewall mounting holes the same pattern for all engines if possible. I keep all thrust lines on the mount as close as possible when the mount is bolted to the engine. I am ready to start designing a couple of airplanes for these 25cc engines. Keeping the mountings the same will make it easy to try a different engine on the same plane. There probably won't be a cowl, at least not at first. I don't think there is enough airplanes for this size (21 to 25cc) of engines. I am not talking about 3D aircraft. Your description of grinding the rear of the engine prompts this question. Did you retain the green plastic backplate cover? I prefer the Weedeaters with the 4 bolt backplate, 21 to 25 cc, and I uses spacers about 5/8" long between the "green" and the aluminum plate. I have a Brand new FL-25 I am working on, I need to make a hub and spacers for it and I will be able to test run it. I will post my results on Two 21cc engines in a another post. Thanks for confirming the metric sizes, for the Toro, they are what I found. I ordered the 8x1mm taps on the net, because I could not find them locally. Check this idea, The 8x1mm bolts for prop retention are not as common as 5/16"-24tpi SAE bolts. The 5/16" bolts are commonly used on conversions of this size so I plan on the rear of the prop hub to have the metric threads and the front of the hub to be 5/16"-24. The rear of the hub needs to be a bit less than 7/8" diameter and the front of the hub will be 1.5" diameter, so there is no chance of it getting reversed. On the Toro engines have you seen both the 2 bbl and the 1bbl carb versions. The 2 bbl version has a different cylinder head and a lot different intake porting arrangement. The exhaust porting is the same for both. I am not talking about the timing of the porting, just the phyical "tunnels" through the cylinder. Have you run your Toro yet?
08-02-2005 | 10:22 AM
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From: Blairsville ,
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RE: Weedeater, What do you think?
Hi Dave, I looked at your Weedeater again. My FL-25 and the two 21cc engines I have, don't have your bigger type muffler. My Weedeaters have the smaller silver ones. I am in the process of making an aluminum muffler for the FL-25. This is a bit of a challenge since these mufflers are held on with springs and not bolts. I see why you reversed the cylinder. I converted the two 21cc Weedeaters first. With the first runnings, I got 6000 RPMs with a 16-8 MA prop. They run pretty smooth so I started modifying. I cleaned up the ports, I opened the intake a lot, I drilled the carb spacer to 1/2", and changed the card to Zama carbs from 32cc MACs. Now I get 7000 RPMs with the same prop. I did one other thing and I am not 100% sure if it was necessary yet but I like the way they run, still smooth and a bit easier to start. I machined .030" from the bottom of the cylinders. 7000 RPMs with a 16-8 prop from 21cc seems like it will be usuable. The FL-25 has more compression to begin with and the ports are also bigger to begin with so I am interested to run it after the conversion is finished. I am going to change its carb also as the main change. I hope it runs as smooth as the 21cc versions. One other point is that these engines are not terribly loud without a muffler so that is why I am making a muffler to try on the 25. (Working on these engines has become another Hobby in itself)
08-02-2005 | 03:41 PM
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RE: Weedeater, What do you think?
Hi rollmyown,
I don't have prop hubs for my Toro single carb or Makita 24.5cc yet, so they havn't bee run. The Makita takes a 6mm. I don't know the pitch for the Makita yet, it is the same as the G23 Zenoah. It would be nice if you could post some pictures. My 25cc weedeater has a four bolt aluminum back plate. I have a 18cc with a plastic four bolt backplate. I trimm them and sand the back plate flat for the mount. I don't have the equipment to turn down the cylinders for compression increase. You really got good performanec from those 21cc weedies. If the 32cc Mac carbs are the same as the 28cc they would be a good choice for the 21cc. Mine is a 10mm Walbro. I planned to use it on my Echo 21cc and put a 11mm on the Mac 28cc. Using a 5/16x24 bolt on a metric prop hub is a good idea. That is how my Echo 44cc is setup. I planned on doing this with all metic shafts and I use a standard bolt pattern for all of my mounts. I hope that I anwsered all of your questions.
Dave
I don't have prop hubs for my Toro single carb or Makita 24.5cc yet, so they havn't bee run. The Makita takes a 6mm. I don't know the pitch for the Makita yet, it is the same as the G23 Zenoah. It would be nice if you could post some pictures. My 25cc weedeater has a four bolt aluminum back plate. I have a 18cc with a plastic four bolt backplate. I trimm them and sand the back plate flat for the mount. I don't have the equipment to turn down the cylinders for compression increase. You really got good performanec from those 21cc weedies. If the 32cc Mac carbs are the same as the 28cc they would be a good choice for the 21cc. Mine is a 10mm Walbro. I planned to use it on my Echo 21cc and put a 11mm on the Mac 28cc. Using a 5/16x24 bolt on a metric prop hub is a good idea. That is how my Echo 44cc is setup. I planned on doing this with all metic shafts and I use a standard bolt pattern for all of my mounts. I hope that I anwsered all of your questions.
Dave
08-02-2005 | 08:55 PM
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From: Up north,
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RE: Weedeater, What do you think?
post what you get for rpm's when you get up to that point, i'm really curious... I've got two 25cc weedeaters serving as actual lawn mowing devices, and one blew out the exhaust. INSANE power once the exhaust was opened up, I rarely trim above an idle!
08-05-2005 | 10:53 AM
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From: Blairsville ,
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RE: Weedeater, What do you think?
Hi Dave, (and smokincrater) I will post what RPMs I get with the FL-25. I am going to try the non adjustable carb it came with out of curiosity and to establish a baseline. Its a single needle version that might be adjustable with a special tool. I ran it before converting, it was brand new, and seemed to be eager to run. The ports don't seem too bad as far as size is concerned, but I won't hesitate to open them if it seems like it will add RPMs. The FL-25 as I mentioned has more compression than the 21cc weedeater had. I also want to see if the 25 runs as smooth as the 21s. I suspect the 25s will be better all around and they are still light. For a Lathe, I have a little Taig lathe so modifying trimmer engines is a challenge, it can be done but not as quick as a bigger lathe. Machining the cylinders was a challenge. I wondered what machining the cylinders was going to do the "breathing" of the transfer ports, I had a plan to round out the tops of the transfer slots if necessary, but it didn't seem to be detrimental and I am to the point of "I better quit while I am ahead". My Taig has paid for itself making non hobby stuff stuff so I use it. It takes me a while to make a prop hub, but after all its a hobby. I do have a Digital camera and can take pictures, but how do I go about posting them? I have never posted pictures. I am probably like most hobbyists, never bored, but with the fingers into too many projects. I have the Toros ready for Prop Hubs but I am cleaning the shop area, they can get out of hand as you know. (If any one else has a Taig, I can offer a useful tip.)
08-09-2005 | 11:00 AM
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RE: Weedeater, What do you think?
Maybe try this [link=http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=33684]Harbor Freight Lathe[/link] instead. Lots of support on the net for it too.
08-09-2005 | 03:40 PM
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RE: Weedeater, What do you think?
Oslim, I bought the Taig years ago when there was not that many choices. Mine has paid for itself, but it is small and the price is getting close to $400. It is neat in some ways but it I wouldn't buy one today unless like a friend of mine I found one used in good shape for $50.
The Taig cannot cut threads, another reason why I would look elsewhere. Hobby Lobby sells the Taig. Maybe the Taig's best feature is that it is small, about 17" long, if space is a problem. I would like another more capable Lathe myself, but then I might need to put my bed outside, this hobby can take over your life, but I am never bored.
The Taig cannot cut threads, another reason why I would look elsewhere. Hobby Lobby sells the Taig. Maybe the Taig's best feature is that it is small, about 17" long, if space is a problem. I would like another more capable Lathe myself, but then I might need to put my bed outside, this hobby can take over your life, but I am never bored.
08-09-2005 | 03:59 PM
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From: Blairsville ,
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RE: Weedeater, What do you think?
runningman, I kind of like that Lathe myself. We typically use 1.5" or so barstock material for prop hubs and since you can't just stick a barstock of this diameter into the chucks of most small Lathes, leaving enough sticking out to machine a hub and then cut it off. This is what we need to work around with, with hobby Lathes. I have to cut off a piece a bit longer than what my finished length will be and then start machining it in steps. It takes me a while to do a hub. I don't know where I would put a Lathe like I would like to have. To machine a flywheel with a Taig was a challenge. The Taig has a 3/8" bore but it was the right size hole to accept 3/8" x 24 threads so I threaded it and now I can bolt a flywheel on. With several different length 3/8 bolts, for different items that I might need to work on, it works. A lathe with a large enough spindle bore for production runs of something out of 1.5" barstock is a good sized machine. These small Lathes are becoming reasonably priced and in spite of small spindle bore diameters are extremly useful for our hobby. I always want to have a Lathe of some kind now. Like a drill press, you get attached to them. Talking about the spindle bore diameter subject could be out of place here, but it might help to point out a main difference between a hobby lathe, possible to have in most home work shops, and a machine shop Lathe in a full size machine shop. A big Lathe with big capacities is very heavy too. A lot of the mystery goes away with Lathes like everything else, once you get your hands on one. These new Hobby Lathes cut threads also.
08-09-2005 | 04:20 PM
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From: Blairsville ,
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RE: Weedeater, What do you think?
To add to my post on the FL-25 weedeater I am working on. I finished the conversion and ran it with the original carb, just to see what this single needle, non adjustable, carb would do. With a 16x8 prop, I got 7000 RPMs and a 3500 RPM idle. This is a main problem with all single needle carbs for RC, there is just not enough flexibility for our use. I then replaced that carb with a 2 needle carb having the same bore diameter, 1/2". This carb produced 7000 RPMs also but with a nice 2500 RPM idle and a bit better overall running characteristics, throttle response included. Then I installed a 2 needle ZAMA carb with a bigger bore diameter, 9/16", like I used on the 21cc weedeaters. The ZAMA gave me 7100 RPMs and ran great with nice throttle response. I suspected that I could get more by porting, so I opened up the exhaust and intake ports as much as I practicaly could within reason. You can go too far. I always keep from filing down to the top of carb pulse hole use for the carb pumping function. Now I am getting a nice running 7800 RPMs with the same nice sounding 2500 RPM idle. It sounds pretty good a t 7800 too, not like a weedeater at all. It would probably get to 8000 RPMs but it would be close to being too lean. I am well pleased with this lightweight weedeater now and I am going to quit messing with it while I am ahead. It could improve with time also, it was new, and only has about an hour at most on it now. By the way, it was easier to trim than the 21cc weedeaters also. After the running test, and while cleaning it up, I discovered the gasket under the spark plug was leaking compression, noticeably, so I fixed that, but didn't run it again. I think it is safe to say that a FL-25 modified like I ported this one is good for right around 8K with a 16-8. I am very pleased with it to say the least. I can help with photos of the porting if anyone wants to see how far I went. I did open it up quite a bit to result in 8k.
09-12-2005 | 09:54 PM
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From: Blairsville ,
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RE: Weedeater, What do you think?
Hi, Harbor Freight has recently built a store that I could get to. I saw the Lathe you have the link to, but it was red, and it had a nice finished and assembled look to it. I wanted to see firsthand the 9" x 20" Lathe. They had one and it was mounted real high up on a terraced display counter. It was hard to check out and I am 6' 1" tall. The side door was a flimsy sheet-metal affair and the gear train covered by this door didn't look all that great either. The door killed my interest and there was so much else to look at that I moved on. It would be smart to see these things before you buy and these stores are springing up in more cities. They didn't have a 7x12 or maybe it is now an 8x12 for me to also compare at the time, I 'll have to go back. You can also call and check on items before you make the trip and burn the gas.
01-11-2006 | 12:29 PM
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From: Avon,
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RE: Weedeater, What do you think?
Dave,
Have you ever run the 18cc weedeater. I have a few of them. I want to open the ports up and run them on EI. It should be 2lbs then. Very light. It is so small with EI it may fit in a 60 - 90 size airplane. I just thought it would be fun to try.
Have you ever run the 18cc weedeater. I have a few of them. I want to open the ports up and run them on EI. It should be 2lbs then. Very light. It is so small with EI it may fit in a 60 - 90 size airplane. I just thought it would be fun to try.
11-09-2007 | 06:40 PM
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From: NEW BOSTON,
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RE: Weedeater, What do you think?
rollmyown,
I have a 25cc Poulan to convert and I would very much be interested in seeing the pictures, if you still have them, of the port mods you made.
Thanks
Jim
I have a 25cc Poulan to convert and I would very much be interested in seeing the pictures, if you still have them, of the port mods you made.
Thanks
Jim
11-09-2007 | 09:22 PM
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RE: Weedeater, What do you think?
rollmyown: Here is a link dealing with Harbor Freight Lathes and others. Good data! Capt,n http://www.rcuniverse.com/forum/m_49..._1/key_/tm.htm
