Thai Longtail/mudmotor With 6hp Lifan/honda

Nice work, thanks for the pictures.

Is there any concern about the engine running tilted? - I assume it is splash lubricated.

 

Not so fast ......well thats basically 20 mph which is what I predicted.If you gear it down you will not increase power ( which drives the boat ) but torque so you can drive a higher pitch prop BUT SLOWER so no gain ...

Your biggest problem is that greased shaft ...6 ft of greased bearing ..that consumes a lot of power and riding the thrust on the motor is not a good idea ....other gains by increasing engine rpm ..look at johns modded engine on the other thread ..weedeater conversion

 

Oil or grease in the shaft tube?

so pistn i was just reading the new posts on here and you say not to use grease. i am in the process of building a go devil type mud motor with a 24hp honda and i am at the point of the project where i decide to put grease zerts or an oil fill plug so what do you think i shoud use? the store bought go devil has a grease zert and a pressurized grease can on it and the tube is filled with marine grease. i was first thinking about using grease i thought it might help keep out any water because its thicker and water wont mix with it, i know it wont mix with the oil either but i could get water in the oil though. any input would be greatly appreciated. i will be posting some pics soon i hope.

 

think you missed the point ...he said he had a tube with no bearings just the drive shaft running in grease inside the tube ...thats a 6 ft long bearing ..lots of energy to churn the grease ....if you had say 3 bearings (ends and middle ) clearly a lot less area and grease to churn

You need a drive shaft say 1/4 inch less than the inside of the tube and push in a T bearing at the prop end with plane bearings centre and top ..Nylon Bronze Brass and grease it before and after use through a grease nipple. that is if you have not got the engineering machinery to handle sealed ball or taper roller bearings . you need a slideing or adjustable link to the motor so its bearing is not used as a thrust bearing ...splines would be best

 

Thanks pistnbroke, although that leaves me scratching my head......

Why do 99% of all outboards always use gear reduction? And marine transmissions also have reduction? Same with stern drives I think, not sure. Maybe there's some gain in going for reduction? Not to contradict you, just trying to help my understanding that's all.

Yes I do understand what you're saying about the grease. Will slower shaft rotation help with the drag?


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outboard engine runs at 6500 not the 3600 of the lifan so they reduce the rpm as the prop is more efficient....comercial tanker about 100 rpm ..I have a real briggs and stratton outboard and they do a 1.53 reduction on the 3600 for the prop ......model boat engine 20,000 straight off the crank though some do use a reduction gear ...

 

oil or grease

sorry for the confusion pistn, i was not talking about notsofast's setup i was wanting your opion on a home built mudmotor that i am building it has a tapered roller bearing in the shaft on the prop end for thrust load, then there are 2 brass bushings spaced out in the middle of the tube for shaft alignment, and then there is a greasable flange bearing at the top of the tube for side load. the flange bearing is not inside the tube though it has its own bracket that holds it in place. tube is totally sealed at both ends. i am wanting to know if you think i should use a marine type grease or an outboard lower unit type oil. i am going to vent the tube at the upper end for oil or grease expansion so i dont blow out the seals. does it all sound feasible?
thanks, muddin

 

best thin oil for bearings would be automatic transmission fluid ..I have that in mine

 

I sure enjoy seeing other guys ideas in photos. PB's will be a big seller among the Lilly pad fishermen.

PB, did you figger that all out with a sliderule before you made the first piece, or did you start making pieces and make them fit later?

 

got a lathe a welder and a brain ..just went to see what bearings I could get etc its not a big engineering problem ..bit crude really BUT IT WORKS !!

 

Why not put your hole at the top like you said and put an oil resoviour on the hole to feed the tube. Something like a brake fluid bottle.

It would also be a kind of tell tale that all was well, if level changed something was wrong.

 

Thanks Pistnbroke, it makes sense now.

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Very nice job Pistnbroke.

What is the diameter of this rod or pin? is this plenty strong? and width of U sections?

~ Michael

 

my us section is a bit narrow ...I would use 2 or 3 inch. the pin is 8mm so go for 1/2 inch ....my main modification would be to set the shaft under the centre of gravity of the engine so the chain would be a little ofset rather than up and down

 

hi I'm knew to this forum i want to build a long tail for a 14 foot john. i was looking at the Greyhound engines at harbor freight.com the have a 2 1/2 96cc four stroke for under $100 and a 6.5 for $160. dose anyone have any experience with with these engines? any advice would be helpful thanks.