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View Full Version : Reverse Engine rotation on a weekeater


Andyinchville2
08-25-2004, 09:38 PM
Hi,

I was weedeating the other day and noticed something interesting.....My weedeater seemed to cut grass off fence lines and walls better when I walked in the opposite direction compared to how I normally walk with the weedeater (I am right handed and use my right hand to operate the throttle and my left to hold the handle of my Shin 270....When I walk I typically hold the head of the weedeater towards my leftand move in the direction of my right arm))....Has anybody else noticed this?......Also when I edge, the weedeater throws dust in the direction of my travel making it hard to see the line I'm cutting sometimes.....Would be great I think to be able to reverse the direction of the engine to make cutting easier....Does anybody know if the engine would run OK spinning in the opposite direction?.... I could probably alter the starting mechanism to accomplish this......(Yes, I have tried walking the other way but you cant teach and old dog new tricks!).....Am I weedeating like you would (hold technique and direction of travel?)

Thanks
Andrew

PS -I know that using cable drive weedeaters the head sping in the "right" direction for me....but weedeaters using a gearbox causes the head to spin in the "wrong" (counterclockwise).

PLM-1
08-25-2004, 09:50 PM
walk the other way...right to left. it will throw the stuff back at you. the arrow on the shield is the direction the head spins. when you edge turn the head vertical and the shaft at 130 degrees and walk right to left. i have never heard of a weedeater spinning clockwise..all of mine have ALWAYS spun counterclockwise (the way it should be..LOL)

GeeVee
08-25-2004, 10:07 PM
The head spins the way it does for centrifigal force. The bolted on parts would loosen if they didn't spin they way they do.

Holding the device the way you do, you would see an increase in efficiency if you traveled around the work clock wise (r-l).

Andyinchville2
08-25-2004, 10:18 PM
Thanks for thinking of that....I forgot that the threads on the head would have to be change changed so they wouldn't loosen if the engine spun the other way.....I tried walking clockwise but it seems so unnatural to me.....

GeeVee
08-25-2004, 10:28 PM
Learing left hand throttle isn't that hard, but you have to be a hair more patient than your average lawndaryl.

One full day tops. AND, you wear a lot less stuff home each day left handed.

(evens out those arm muscles for two fisted drinking, or ambidextrous pud-pulling, for the Gedd types.)

Ric Harris
08-29-2004, 04:24 AM
I use a 13 year old HomeLite ST-275 weed eater with a rapid feed head and .155 line. I'm right handed also, and with a clockwise spinning head the days of walking from right to left are gone. My helper uses the counter clockwise spinning Echo trimmer and at the end of the day, the boots tell the story. You can "LOL" at the name but that ST-275 will put some of them Pro weed eaters to shame!

ric.

Envy Lawn Service
08-29-2004, 04:52 AM
No reason they can't make then spin the right way!

Commercial trimmers suck!

Slow, unefficient for the right hander and filthy!

I like the rotation better for edging though.

Anyways, the first commercial trimmer made that spins the right way will get my business immediately!!!!!!!!!

Sometimes I want to go back to Ryobi straight shaft trimmers. Last one was a split shaft and held up 2 years running all the attachments.

Andyinchville2
08-29-2004, 12:34 PM
HI,

Thanks for some of the responses...I haven't had a chance to look into reversing the direction of the starter mechanism and changing out the threads at the bottom but I wonder if anybody out there has actually done this already (modifying a weedeater to spin in the opposite direction from the manufactured way)...
I think it would help alot to make a weedeater than can be reverse rotated for us right handers.....

Andyinchville2
08-29-2004, 12:37 PM
Just thought about it but I did ask the dealer if they knew a way to make the head spin the other way and they just scratched their heads....I wounder if there aren't alot more lefties out there
cutting grass than us righties....I mean there has to be some reason why all the manufacturers get the heads to spin a certain way?

Pecker
08-29-2004, 12:58 PM
I too liked the clockwise direction (when operating the trimmer, looking down at it as it cuts, the string spins clockwise) of my Ryobi. The reason I like, as a right-hander, is because it allowed me to trim left to right and it throws the leaves and debris out away from the fences and structures so that it can be mulched by the mower. Since I'm still right-handed and must go left to right (vs. having to twist my upper body to trim right to left), the commercial trimmers just throw the debris up against the fence and the end effect is not so great because there is still debris near fences and structures that can't be mulched by the mower.

The only reason I can think of that they would do this is to counteract the effects of the mower blades, since they all seem to spin clockwise. I noticed in places, such as curbs, that over time the grass wants to start growing laid over slightly in the direction that the mower blades travel. Since the trimmer works in the opposite direction it stands the grass back up, and makes it look good.

grass_cuttin_fool
08-29-2004, 01:09 PM
I have one of thoose Home lites also, I really tuff trimmer, I have retired mine, it needs a rebuild kit in the carb, gas runs from it all the time

tx_angler
08-29-2004, 01:11 PM
It would be almost impossible to reverse the stroke of a two cycle engine because of the intake/exhaust port alignment within the cylinder and the location of the reed valve.

See this link (http://science.howstuffworks.com/two-stroke2.htm) for an animation of a two-stroke engine in action.

Five Diamond Lawns
08-29-2004, 01:15 PM
Just get an EDGIT attachment for your weed eater and for get it. It'll cut up next to a chain link fence like a dream!:blob3:

The C Man
08-29-2004, 02:03 PM
Originally posted by Andyinchville2
I wonder if there aren't alot more lefties out there cutting grass than us righties....I mean there has to be some reason why all the manufacturers get the heads to spin a certain way?

It's not a conspiracy even though it might seem that way. The drive shaft on all trimmers spins clockwise - it's how it connects to the head that determines if the head also spins clockwise. On a curved shaft trimmer the drive "shaft" is a cable that attaches directly to the head, so the head is obviously going to spin clockwise too.

On a straight shaft trimmer the drive shaft goes into the gear box, then into the.... can't think of what it's called... the reduction gear? .... then that attaches to the trimmer head. This setup causes the head to rotate counter-clockwise.

fubunics
08-29-2004, 03:06 PM
What is a 'week eater'?!? :D I'm left-handed so I don't have this problem. Although I will say that my legs get covered in dirt and grass and I get plenty of crap kicked back up into my face trimming left-handed, so I really don't think it makes much difference there. I have a Ryobi split-shaft and a kawasaki, and if they rotate in different directions, I guess I haven't noticed it.

TClawn
08-29-2004, 03:24 PM
fubunics, I am also left handed and there is a way to hold the trimmer so that you don't get junk on your self. tilt the trimmer slightly to your right so that your cutting with the back of the head instead of the leading edge. this only works in growth that is not super heavy but for weekly matinence it should work just fine.

fubunics
08-29-2004, 04:50 PM
thanks for the suggestion TClawn, I'll have to remember this...

EJK2352
08-29-2004, 04:52 PM
Originally posted by Andyinchville2
HI,

Thanks for some of the responses...I haven't had a chance to look into reversing the direction of the starter mechanism and changing out the threads at the bottom but I wonder if anybody out there has actually done this already (modifying a weedeater to spin in the opposite direction from the manufactured way)...
I think it would help alot to make a weedeater than can be reverse rotated for us right handers.....

I changed the rotation of my Echo SRM-2400 from counter-clockwise to clockwise. I took a gear box from an old Stihl FS 66 and mounted it on the Echo. The engine on an FS 66 turns the opposite direction than the Echo and most other straight shaft trimmers. So mounting that FS 66 gear box on the Echo gives me a clockwise spinning head. I put some blue locktite on the threads of the head and socked it down as tight as I could. I have not had any problems w/ the head coming loose. I use a Gator Head and have to wind the string in the opposite direction than the spool indicates. It has worked flawless for 3 seasons. I used bent shaft for years and could never trim near as fast w/ a straight shaft as I could w/ a bent shaft. Now I can fly w/ the straight shaft Echo, reach under decks, trim wide ditches and edge better than a bent shaft. The Echo is getting a little tired, so I am now working on converting a Redmax straight shaft w/ the FS 66 gear box. My cousin works at a machine shop and is machining the splined driveshaft to a square so it will fit the Redmax. The Echo has a square flex shaft that fits the Fs 66 gear box without modifications, since Stihl uses a square ended solid drive shaft on the FS 66. I tried to use the Redmax as it was from the factory, but I am so unproductive with the counter-clokwise spin I just couldn't use it. I'll try to post some pictures of the Echo.

EJK2352
08-29-2004, 05:33 PM
Picture of Echo w/ FS 66 gear box.

EJK2352
08-29-2004, 05:34 PM
Another picture of the Echo

EJK2352
08-29-2004, 05:35 PM
One more of the Echo

docta
08-29-2004, 05:54 PM
I'm new to the forum and to the business, however I feel as though I can make a comment regarding your weed eating. I'm also right handed and when I'm trimming along a fence, wall, or anything vertical to the yard, I trim from left to right or opposite to trim head revolution. I wear chaps for protection. Personally, I feel as though I have much more control that way. Got tired of the trimmer walking up fences and the like.

Expert Lawns
08-29-2004, 06:17 PM
I always walk backwards and from right to left. This seems to pull the grass away from the mulch/flowerbeds. When I go the other way, more grass seems to fling into areas that I dont' want it in. Also, when you go right to left, it pulls the grass UP from when you went by it on your mower.

Harry0
08-29-2004, 06:59 PM
I use the curved shaft for the clockwise rotation-And I am an old dog-I have used the straight shafts but I scalped and got frustrated-So I use the curved-Harry

Andyinchville2
08-30-2004, 12:42 AM
HI Tx Angler,

Thanks for the link....that site has alot of interesting info in it....Between that and lawnsite I may not get anything done!.....Anyways I did look at the movie of the 2 cycle engine but I still cannot see why engine rotation would not work in reverse....I mean the piston would still just go up and down just the crank wouold be spinning ion the opposite direction or is there someting else that I'm missing?
Thanks
Andrew

Andyinchville2
08-30-2004, 12:51 AM
I just thought about it but anything cable drive (curved shafts and some of the old cheap homelites straight shaft Homelites I had would spin clockwise)....After getting used to the power and durability and smoothness of the shin t270 and soon to be t350 I'd really hate to go backwards to the old cable drives....I really am going to try to make it clockwise tho!.....

I really like the idea of using a different gear box but that seems like alot more cost and possible work in the event (most likely) that it wouldnt work on my shin w/ extensive machining etc....

When the shop opens tomorrow I think I'm going to order a manual (other than the owners manual) for my machine and I'll study the poics to see what if anything can be done...Hopefully easily.....

In the event that the whold reverse engine thing works do you think loc tite would be enough to keep the nuts and bolts from loosening i8f I am able to change the spin direction of the head?.....Now they tighten in the direction of headspin but If I reverse the direction of the engine the rotation would tend to loosen the assembly....I think (hopefully) high strength loctite would work?
Thanks again
Andrew

Andyinchville2
08-30-2004, 01:00 AM
HI Ejg2352,

How did you know that the different heads would interchange....trial and error? Any ideas if the head would fit a shin t270?....I 'll get the maunal on order to see what kind of shaft ends I have....Oh, was the fs66 a cable drive or shaft drive and are there gears in the head assembly?.

Thanks
Andrew

EJK2352
08-30-2004, 01:17 AM
Originally posted by Andyinchville2
HI Ejg2352,

How did you know that the different heads would interchange....trial and error? Any ideas if the head would fit a shin t270?....I 'll get the maunal on order to see what kind of shaft ends I have....Oh, was the fs66 a cable drive or shaft drive and are there gears in the head assembly?.

Thanks
Andrew

What do you mean when you say different heads?? The gear box or the line head?? The FS 66 had a solid drive shaft w/ square ends. As far as expenses in your earlier post, the gear box I have on the Echo came from a tired FS 66 that was no longer in use. The gear box that I'm going to use on the Redmax, I found it on Ebay. What is the diameter of the outside of the shaft tube on your T-270.

EJK2352
08-30-2004, 01:28 AM
Andy,
I went to Shindiawa's wed site and according to their trimmer specs. the T 270 uses a splined drive shaft. They also have a parts PDF parts breakdown available on their site. My cousin is remachining the driveshaft for my Redmax, and it was a splined shaft. He said it's a 10 minute job. I'll let you know how it works out once I get it all together.

Richard Martin
08-30-2004, 05:03 AM
Originally posted by tx_angler
It would be almost impossible to reverse the stroke of a two cycle engine because of the intake/exhaust port alignment within the cylinder and the location of the reed valve.

The port alignments, port timing and reed valve work the same way no matter which way the engine spins. Also most of these small 2 strokes don't have reed valves. If you actually look at a 2 stroke engine and spin it both ways you will see this.

There are 4 issues with making a 2 stroke engine reverse rotate.

Two have already been discussed here.

1: Starter
2: Bolt and nut threads although this is not really an issue
3: The clutch would need to be turned upside down (if possible) so it engages with the opposite rotation
4: You would need to spin the flywheel 180 degrees on the crankshaft so the spark plug fires on the other side of the engine rotation.

Andyinchville2
08-31-2004, 01:08 AM
Good point about the clutch, I haven't torn into one of my older shins yet (may do this this weekend).....I suppose though it depends how the shoes are held in and where the pivot points are that determines how the clutch has to be modified....If everything can be flipped over (starter / clutch) that would almost be too easy.... I'm sure probably some modifying /customizing will be needed......

I'm not sure I follow about the flywheel though....is it possible that the flywheel can remain as is? or at most changed just a few degrees to accomodate the reverse rotation (example: a 4 cycle car engine (assuming clockwise rotation) usually runs a few degrees of advance on the distributor....However, if the same engine were reversed, the advance would effectively now be a ******.....in this case the timing would need to be changed by the amount of the initial advance setting.....I assume by the 180 degree change you mean taking the flywheel off and (if side "a" was facing away from you turn it around so that side "a" is now facing you) or do you mean that if point "a" was at the 12 oclock position that you would move it 180 degrees so that point"a" is now at the 6 oclock position.....I guess in thinking about it the first change seems "more" reasonable but I wonder if the flywheel could be left alone......Hmmmm now that I think about it I wonder how the cooling would work....I think the flywheel has fins on it to blow air.....maybe it would have to be switched after all......

The more things that pop up makes me wonder it wouldnt be easier to simply (yeah simply (said sarcastically)), eliminate the gears at the shaft end and replace it with a small u joint or cv type joint....this would automatically change the head rotation since the unit would effectively spin in the direction like a like a cable drive unit at that point....

Richard Martin
08-31-2004, 03:37 AM
The flywheel would have to be turned past TDC by whatever the timeing is advanced. If the plug fires at 20 BTDC then it would have to be turned past TDC so it fires on the reverse rotation at 20 BTDC. I just used 180 degress to give you an idea of what has to be done. Timeing is critical on a 2 stroke and incorrect settings can lead to a meltdown (been there, done that).

The cooling is kind of "iffy". Under normal usage it should be okay but if you get into some heavy bush wacking it probably won't be good enough.

Your Shindaiwa clutch should be made of 2 heavy shoes with springs that hold them in the closed position. These rotate inside of a drum.