Weed eater engine conversion

success

spent an hour goin up and down the river today and worked so well, low speed was a nice criusing speed, high speed was lots more powerful than the electric trolling motor. the real gem was chopping through the weeds like never before, after the test the river had a nice channels through sections that had been chocked with weeds. never cutout or stalled if cruising slow into some weeds you just had to rev it up a bit and they would come flying off, some bits can be seen on the image below.

the only camera i could get for video with sound was my crappy old phone but here is a bit of footage, http://www.youtube.com/watch?v=bj8t0iJKgNM
and http://www.youtube.com/watch?v=raSkoMJSllg .

added a 90 degree bit of aluminium to the muffler to redirect the sound away from the boat and was not real noisy at all. had also cleaned out the muffler and added some baffling to the inside of it to also bring down the noise a bit. the prop seems to like running best about 3/4 in the water but likes being just submerged at high speeds, for gettin through thick weed having it in water about 50% did a great mowing job and kept me moving.

will be able to shorten the drive shaft by about 20cm but will wait until there is a need. was a total buzz and better than hoped for. machined the plastic parts and bolts to make the depth collar and be able to lock the shaft partially to assist with steering. was able to steer well and corner well, even spin it 180 degrees and run in reverse which i had not even hoped for. it spins a full 360 degrees without anything gettin hooked up.

not much left to do now except get the fishing gear together and go enjoy it, saw fish swimming past the same as when using the electric motor, was able to cover the same area so much faster and easier and many times and when done still had over 1/2 a tank of fuel left. carrying the motor down and up from the river was also lighter than the smallest electric setup. am very happy with this build, looking forward to seeing how far one can go with a full tank of fuel in a bigger river

 

this thread is awesome, after seven years who is the winner

 

part of the secret as well as the 10 to 1 gearbox is that the clutch does not come in until about 4000 rpm so there is some torque available to turn the prop without stalling ...the thai longtails all seem to have some gearing ...great job now all you need to do is learn to take a video !!!!

 

We all are.

 

I was finally able to get out an test my build again. I after the last test run in the fall, it was clear that I had to remove the clutch because it was slipping and getting really hot.

All in all it did pretty well for being a little weed whacker. I had a pretty average top speed of 4.6 mph according to my GPS, but I need to look at all the data for an official number.







Erich

 

Erich that is an impressive conversion you have there. looks like it gets along well, do you know if there is any gearing in use or just a bigger motor and small prop with high pitch?

have reviewed the gearing on the redmax and its not as high as first thought. The gearbox is a two stage 35:17 tooth gearing giving about 4.25:1 ratio, the rest of the gearing to get the stated 7.87:1 is in the reciprocating head which is not used for this project. as the rotating head i did use though has 1.25:1 ratio the final ratio for my setup is about 5.3:1 and is working well so far.

have been trying to design a cheap gearbox all week that other could use/make but gears cost too much online to make it practical and the machining to make a gear housing takes quite some time and needs to be accurate so will give up on that idea for now unless someone else has gearing ideas. the nicest would be an inline planetary gearbox that could handle the torque, then it could be added to any unit, something similar to a rechargable screwdriver.

is raining still so have not had a chance to make a better video, hopefully over the weekend, the river is up from the recent rain and will be able to test going against a bit of current much better. found another redmax unit for parts at dump this arvo and a stihl with straight shaft to use the 45 degree head on it, got both for $10, will spend the night cleaning them up. since i hope to get 2 working units going will for fun try running a dual motor setup as well to see how it goes.

 

Rifraf,

There is slight gear reduction in the gear head at the bottom, about 1:0.7 if I recall but that's it.

Sounds like your well on your way with your project. I wish I had a dump with so many usable parts for so cheap!

Keep us posted with your progress.

Erich

 

another success

tested the other motor today in the river, was all good, after 2 hours still had fuel left.the video quality is a bit better but no sound sorry.
going upstream looking behind http://www.youtube.com/watch?v=Wlmawoxu43c
goin upstream looking forward http://www.youtube.com/watch?v=CjdClmSng-w

 

for gods sake stop waving the camera about ..just a nice steady shot of the back of the boat with the outboard the banks and the wake //// if you moved your head like that it would fall off ......

 

heh was the best i could do for now, will get a camera person to do it next weekend so i can just steer. the issue is i need to move the bottom bracket out about 10cm to get a better angle on the prop, and was hard to hold it out at that angle with one hand, will make a few new brackets durin the week, and have not inflated the boat for a few weeks so made it a bit sluggish, needs some more weight in the front end so might pack some gear for next test or get an extra person

 

Mark Wo., Just a brief up date.

I finally, heavy on the finally, have assembled the parts for an affordable and light reduction for these things. I am going for 3 /1 reduction to the drive shaft. It came in at maby 1 lb and $30.00. I' m mateing it to a bronze 6 x 4 prop on a 5 /8 " shaft 60" long. The houseing organizeing it all is at the laser now. When I assemble it I will get some photos of it being put together. I am useing the Robin 1.6 hp 4 cycle motor with its integral clutch. My brother the boat builder is putting a fiberglass boat together for this thing. He wants to run his trap line next fall with it to eliminate the paddle between sets. Thank you for your encouragement over tha past years on this thing. It has helped to keep me focused on following this thread and every bodies efforts to solve the light motor question and its importance to so many people.

Mark F. Cheney

 

hiya mark c,
would be very interested in the parts you found for the gearing as have been trying to achieve the same thing, well i have the gearboxes but wanted a way for anyone to be able to do it as well. could your design extend to a 2 stage gearbox to reduce it even further to like 5 or 6:1?

 

rifraf, I finally bit the bullet and had a J profile micro groove 4" pully made from glass filled nylon for the driveshaft side and am useing a 1 1/2" diameter input shaft pully. this is a 6 groove belt. Belt tension is maintained with an idler pully on the slack side of the belt. Center distance on the pullies 3 3/4" The saasy fits in a box 7 1/2" by 5". made of formed and welded aluminum. The motor bolts to one side and the output shaft assy bolts to the other side. There is an inspection plate bolted to one side to allow it to be put together and to keep things out of the belt. I have had experiance with this belt system with ultralite aircraft drivesystems and have confidence in it. It has taken me a while to figure out how to get the weight out and get tooled for the 4 " pully. So far I only have a single set of pullies and clutches. 5 /1 would require a 7 1/2" large pully and a longer center distance to enable the small 1 1/2" drive pully to grip the belt. I have seen such an arrangement before. I just don't have tooling for that large of a pully. I have had it bid before and seem to remember a price of something under a $100.00 US for at least 2. I don't have my case back from the laser cutter yet. I'll post some photos when I do and figure out how to post them.

Mark F. Cheney

 

Mark,

I look forward to seeing your new set up.

Posting pics is pretty easy when you use Photobucket.com. Sign up for a free membership, upload your pics and then copy and paste the "img" code for each photo you want share in a new post. Piece of cake!

Erich

 

you dont need photobucket

you dont need photobucket and all that crap just load into your computer under my pictures ...go to Advanced and click on attachments ( looks like a vertical paper clip) then attach them .browse and upload ..easy