Weed eater engine conversion

drive tub material

Drawn over a mandrel, DOM, seamless material is made to very close tolerances in either steel or aluminum. Both of the ID and OD will be within
.001 of nominal stated tolerance. The problem is that the bronze bearings are often as much as .003 - .004 oversize. Often it is possible to press them into DOM outer sleave material, but not always.

The big problem for most people is that one usuallly has to buy the DOM material in full stick lengths. Up to 24' in steel and 12' in aluminum. And it is way more money than ordinary seamless tubing.

Mark F. Cheney

 

Thanks for the help guys

 

Wow this post has truley become amazing. Mark F Cheney..father of Utah Marsh moters got on here..fellas Mark is a master at building these moters. Now all we need is a few guys from Bevertail or go devil..lol

Cool to see you on here Mark. Thanks for your input.

 

Hey Mark.....

Hey Mark -

Long time since we ahve chatted. You ever get that small motor we discussed a year or so back up and running? Would sure like to see what you came up with.

You should see the pics of my current motorized project. I'll have to wait until I get closer to completion.

Hope all is well with you.

Mark W

 

progress,

Mark W.

I have purchased 3 motors for this project: a honda 4 cycle, 2.5 HP, and 2 Robin 1.6 HP 4 cycle motors. I spent $1,000 on clutch development that came to naught so far.

I have followed this concept on the various forums now for about 3 years. I have been impressed with the tenacity with which you have worked to get something together for your self. I think your input has helped a lot of people along the way. I even have a fellow in a neighboring city who is currently working on one following your pattern. Good for you!

It appears to me that people are trying to achieve the following:


They want to do something themselves - one of the great american freedoms.

They want a LIGHT motor. My light 7 HP OHC has a following. But lots of people still find it too heavy for their perceived wants.

Price is also a big issue with lots of people.

There are tens of thousands of small boats out there for which the 25 lb motor is ideal for. As trespass rights become more and more difficult to come by, This small boat Idea helps lots of people with this difficut access problem.

For all of the above I have still stuck with working on it. I now have a decent clutch and drive shaft together that can be commercially produced at a decent price. It is based on the Robin 1.6 HP 4 cycle. I have chosen this because it is affordably available to me in quantity. It is very reliable. I know of large samples of this motor running1,800 hours with schedualed maintance.

The last big hurdle seams to be either to get a cheap shaft reducer or build a prop that will function at the RPM's of these small motors.

I have not been able to come up with an affordable and reliable reducer. I have come close to getting an effective prop made for the RPMs involved. It is made of stainless steel rather than the cast aluminum that is popular. I understand the cast aluminum and appreciat its advantages. It's principle disadvantage seams to be that it is not optimally engineered for this intended useage.

I have found That the torque curve of 4 cycles is closer to needs than the curve of a 2 cycle. so maby the Robin will work.

My experiance also says that properly harnesed on of these small motors will push the "small" boat the requisite 5 -6 MPso Yess Mark I am still working on this. The bigger motor business has gotten in the way a bit, but it is slowly comeing together. Thank you for the enquiry.

I am slowly learning how to post pictures and will try to get something up here soon as I am working on some to update my web page too.

Mark f. Cheney

 

Thanks Mark

for the compliment. Much credit for what has been going on in the world of the mini mud motors lies elsewhere - Turn for Fun, John O'Neal, Piston Broke, just to name a few. It has been fun to watch this all come together over the past couple of years.

I'm still not at where I want to be on the mini mud motors. The Duropower was a nice unit that could be built by anyone and it was more than enough to push a small duck boat. The Rickshaw that I purchased used this summer is a nice design but it is expensive (not for what you get but it is just expensive as it is a commercial product). I still think there is room for improvement and the units from Thailand may fill this void. I also think there is something to making a mini surface drive unit like the mud buddies and others. It should be easy enough to do and there exists cheap ($25) bolt on 3:1 chain driven gear reducers to make it real easy. Just have to find the time to look at it in more detail.

Can't wait to see what you come up with. I always liked the thinking that goes into your designs.

Mark W

 

thai longtail

john,
the longtails you got from thailand what is in the shaft tube brass bushing or sealed bearings? is the tube filled with oil? what holds the shaft in the tube?

 

The Thai design is simplistic yet ingenious. It uses bearings made from a self lubricating form of plastic. They come with a limited lifetime warranty. The warranty is ambigious at this point and needs to be better defined. I have an outboard (Cruise-n-Carry) that uses this same type bearing system . It is well over 20 years old, I am told, and is still works great. No oil ,no grease, just fire it up and go.

 

I've been reading this thread, and several others, for the last few days trying to figure out which type of motor would best fit my needs. I think I've decided to build the lightweight style using a 52cc engine. I've looked at the 2-stroke scooter engine, with electric start, on the ms website but also found a 2 1/2hp 4-stroke at hbf. To anyone thats had experience with either or both, which did you prefer?

 

Scroll back or search for my posts... should explain in detail

 

Squirrel 78 ...if weight is not a problem always go for the bigger engine ...you can always slow it down but you carnt upgrade on a 52cc when its flat out .
In your design remember if you go stright off the shaft you need a left handed prop....the bigger the engine the easier it is to match a prop to it ....

 

Thai bearings are almost none existant . They dont seem to attach much imoprtance to it. If the shat turns what more do you want.

However the bearings are made from wood, what the wood is I dont know but it is kept in big tanks of water and is soaked for years, they are fitted to a 4 jaw chuck and tuned out.

Sea Trawlers big shafts of 6 inches plus use the same technique, being turned slightly slack so when pushed home is perfect fit. I asked how long these bearings last he said 2 years.

 

The wood they use for shaft bearings are made from a wood called lignum vitae. It has self lubricating properties, and is commonly used for propellor shaft bearings on big ships and turbine bearings on hydroelectric dams.

You can find it in alot of places that deal in exotic woods.

Bob

 

What is the name of the plastic? Can you post a link to it?

 

and the wood bearings on ship prop shafts and HE run at very low speeds below 100 rpm .....???