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Re: Homemade outboard motor using briggs 2hp

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In Reply to: Re: Homemade outboard motor using briggs 2hp posted by KenOhki on February 27, 2003 at 16:20:20:

whew, man I forgot what a pain it is to draw in autocad! Its almost 11pm so I will just post the dwgs and comment later. I really appreciate your input here and I will respond with my thoughts but its late and I am going to kick back with my black labrador Ziggy for a bit before bed.
here are the drawings - not to scale nor accurate - just conception type drawings
http://machnumber2.50megs.com/photos/outboard2/dwg/one.jpg
http://machnumber2.50megs.com/photos/outboard2/dwg/two.jpg
http://machnumber2.50megs.com/photos/outboard2/dwg/three.jpg

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Re: Homemade outboard motor using briggs 2hp - KenOhki 19:32:12 02/28/03 (18)
I sent you a email to the address on your post with a picture of something I dreamed up. I didnt have room on my webspace to put it up and could not find a way to stick it here. Anyway. Catch ya later
- Re: Homemade outboard motor using briggs 2hp - machnumber2 21:55:55 02/28/03 (17)
  Hi,
  That is a great idea and would definitely work. Its like an o-ring type seal only wider like 20 o-seals in a row. Regarding the clamps I would double up at each end on the rubber shaft area. I would do this out of concern that the clamp would not apply totally even pressure all around the circumference, I assume just under the screwhead of the clamp the pressure ( or tension) might be less then at the rest of the areas, so I would put one hose clamp with screw at top then another right after that with screw at bottom then ditto at the other end. This is just my assumption on hose clamps, its probable that they do provide even pressure throughout. We have to make sure that the lubricant does not eat rubber. I have tossed so many ideas in my head about how to keep the water out but they were all variations on the same thing, trying to make a conventional stuffing box, your idea is original and elegant I like it. For my project I finally gave up and bought a conventional stuffing box that would fit a 5/8" shaft, it cost $30 at the shipyard, and is missing the jam nut but I was pleasantly suprised I was expecting to pay more. Since I have it, I am going to play it safe and use that. I was thinking about your idea about the flexible shaft. It solves a ton of problems at the outboard lower end. The concerns I have about it are: 1. I would have to find a flexible shaft or search for a used weedeater or similar. 2. I would probably have to make it a direct drive onto the motor. Since the briggs turns at 2000-4000 rpm and my prop's max design rpm is 1400, I must have a way to vary the engine/prop rpm. So if I used a flex shaft I would have to hook it up it to gears or pulleys to do that and that would complicate things. 3. I am concerned that the flex shaft will be able to handle the torque of a 2hp engine, and in the future if this things works I want to put a 5 hp on this lower end. My original idea was to use a vertical crankshaft engine and attach a vertical shaft directly to the output crank, send it down to the lower end where it connects to a right angle bevel gear drive where it does two things - reduces the shaft rpm compared to the engine rpm and also of course takes a vertical spinning shaft and converts it to a horizontal spinning shaft. I could not find any right angle gear that was less than $200, and the ones that I did find were like for some heavy industrial use. Nor could I think of any old appliance or junk that uses a right angle drive that I could scavage. I gave up on that Idea and decided to go with belt drive. The belt drive allowed me to simply use varying size pulleys to vary the engine/prop rpm ratio. I expect that if/when I get this thing built, the prop RPM will not be correct and I will have to trial and error different pulley sizes to achieve the perfect rpm so that the engine power is used most effectively, so that there is not cavitation or other problems..., the pulleys allow me to do that easily. I could also use an idler pulley between the drive and driven pulley to act as a clutch that I could have both neutral and forward speed. I then got greedy and wanted reverse. I started searching for a simple gearbox that have forward/reverse on the internet but again the ones I found are for industrial use and very expensive and I could not think of where to scavenge one so I gave up on that. My goal here is to make this thing work so that I can put it on a skiff to cruise the harbors here in southern California with my wife. It would be great if I could watch this old motor live again and be useful.
  - Re: Homemade outboard motor using briggs 2hp - KenOhki 17:01:35 03/01/03 (16)
    Its probably for the best that you got a real stuffing box. I know my idea would work, but I also know it would have eventualy given out after a unknown amount of time.
    Gearbox huh?. I would be looking for a old junked out lawn and garden tractor. some of the real old ones have a gearbox you might be able to adapt. Mind you Im talking old. Other then that,forward and a tentitive neutral will be all you get.. I dont think I would bother personaly But,, Using a centrifical clutch, like on most minibikes might be a decent way to achieve the neutral objective. I would think trying to do it with a idler arm might cause the belt to jump its pully, or not be able to provide the grip you need on the belt when it comes time to turn the shaft. It would be a real pain if the belt came off the lower pully out on the water wile trying to idle in neutral.
    - Re: Homemade outboard motor using briggs 2hp - machnumber2 12:01:41 03/02/03 (15)
      Tried ebay for the gearbox, no dice. The centrifugal clutch is not a bad idea..where can I get one where I can just drive and pick one up other than have to order it? The ones I remember when I was a kid were really noisy though, like a sledgehammer hitting steel 3 times a second.
      I am concerned about the idler pulley causing the belt to come off too, but even with a clutch I must have a way to take up slack in the belt. If I weld this thig together to exactly fit the belt, it may stretch later or I make be 1 inch off etc. I thought it safer to be able to loosen tighten the belt at will. I pretty much got done with the drawing except for the idler pulley assembly if I do that. I found a smaller drive and driven pulley to use (1 3/4" drive and 3" driven) so the lower PVC T in the drawing will hopefully be much smaller than shown. I estimate that this thing is going to weigh in at least 50 lbs with motor (the motor is about 30 lbs I think). I might just start builing this thing and wait and see what it looks like before dealing with the idler/clutch issue.
      - Re: Homemade outboard motor using briggs 2hp - KenOhki 14:34:56 03/02/03 (14)
        
        In Reply to: Re: Homemade outboard motor using briggs 2hp posted by machnumber2 on March 02, 2003 at 12:01:41:
        
        well, using a idler arm at a set fixed tention is fine, but planning on using it to lax the belt to create neutral is what my concern was.
        I am asuming your motor will be bolted to your framework, Keeping that in mind, tention is just a few washers away. Once the belt has stretched the first time, It should stay at a constant size for most of its effective life.
        were I to want to go buy a clutch, I would go to any small engien shop in the area, we have several too choose from,, I am In Maine, SO I have very little Idea what stores you have in your area, But YOu have to have small engien places around,Someplace that services GO-Karts & such. Most Snowmobiles use them too, Again, I am used to scrounging used parts for my prodject..Many years ago I bought one for my 5 hp minibike,, I seam to remember it being like a $70 thing new back then. BUt I do not remember any pinging sound. The clutch I refure to is a cintrifical clutch. With this clutch, the belt was semi loose at low rpm, but as it spun up to speed, the sides closed in on the belt, ( the sides being beveled ) and this tentioned the belt automaticaly.This could be an expensive buy new but if you want a dependable neutral, its the only real solution I see wihtout getting bulky,or using a actual gear box. or using questionable methods. I have sean another type of thing, I would call it a throwout gear, but Im not sure of its real name,, as the engien spins up it throws itself out to engage the drive pully, Kinda like a starter motor on a car works.. I have also seem a manual version of this built by my father some years ago to power his own version of a powered wheelbarrel. But as I remember, his mecinism was crude at best, and regualry broke and required maintence.
        I just looked over the web real quick, I failed to find the clutch for the belt drive I have mentaly pictured, FOund a few for chain drive, 25 bucks or so used on Ebay.. anyway.. Hope at least something here was usefull too you ;p
        Perosnaly, Turning the motor off would be neutral enough for me on the scale we are talking about,,, I cant really see many preactical uses for letting the engien run when not actualy powering the boat
        forward. The only reasons I have come up with are minor too say the least. My 6 hP evinrude has been stuck in forward since the third time I used it, and I really cant say it has affected me, It starts just fine in gear.
        Ya know, Im a little surprized that nobody other then myself has piped in any input here. I do concider my advice sound but am very shocked nobody has piped in either negitivle or positively for that mater. another week or so of posts and our conversation will take over the whole first page hehehe. Talk to you later.
        
        Re: Homemade outboard motor using briggs 2hp - machnumber2 14:53:31 03/04/03 (0)
        
        In Reply to: Re: Homemade outboard motor using briggs 2hp posted by KenOhki on March 02, 2003 at 14:34:56:
        
        Making the set screw holes might work fine, these are like industrial grade bearings, the spec. sheets on them actually gets into the 1000's of pounds capacity. The reason I got them was because they were the only ones I could find. So I am thinking I will try the holes first rather than deal with a thrust bearing adding to this design. As for the math, I dunno I am just thinking back to high school physics I think. They numbers could be way off and it was kind of odd that it did not account for boat mass. The truth is, I do not have a boat lol. I plan on putting this in a garbage can full of water to test it and if I am lucky maybe I can rent a skiff to try the motor out on or maybe somebody else will test it out for me on thier boat. I figure the boat plus people (up to four) and everthing might be like 700-1000 lbs, pretty heavy for that little motor but then again it doesnt have to push it that fast. (the reason i came up with 5 mph is because that is the harbor speed limit, I want to be able to keep up with traffic so we dont get run over by some huge yacht). Piping the exhaust to the water is a great idea, the motor is going to be louder than your normal outboard. I wonder if piping it to the water would make it quiter. Are exhaust threads on these things pretty standard? I wonder if a threaded copper or plumbing pipe would screw right in where the muffler goes.
        
        Re: Homemade outboard motor using briggs 2hp - machnumber2 10:29:41 03/03/03 (12)
        
        In Reply to: Re: Homemade outboard motor using briggs 2hp posted by KenOhki on March 02, 2003 at 14:34:56:
        
        I like the sound of that throw-out gear, like in a car starter. I will look for that as I am building. lol about about our conversation taking over the first page, we should probably be taking this to emails I guess.
        Your previous question on a different post brings a problem to my attention here. (I think I screwed up on the calculation on your other post, will look at again) Plus this guy emailed and said that I was missing a thrust bearing at the lower end, otherwise the shaft will slide thru. The bearings do have set screws in them, if I cranked them down would that be enough to hold the shaft in place. From your last question I was wondering then if an estimate could be made on the shaft force involved. Couple of assumptions, say max speed of this outboard and boat is 5 mph (2.2 m/s) and it requires the full 2hp (1500 watts)to push it a 5mph then from power = work/time or power=(force*distance)/time noting that distance over time is speed then power=force*speed or force=power/speed
        f=1500 watts / 2.2 (m/s) = 681 watt seconds/meters = 681 newtons
        since 1 newton=.224 lbs
        f = 152 lbs
        jeez that cant be right
        If I have two bearing each with 2 set screws each screw will have to hold 40 lbs thrust or so.....but that 152 lbs seems really high I dunno
        
        Re: Homemade outboard motor using briggs 2hp - machnumber2 10:53:32 03/03/03 (11)
        
        In Reply to: Re: Homemade outboard motor using briggs 2hp posted by machnumber2 on March 03, 2003 at 10:29:41:
        
        that 152lbs cant be if that were true then lets say you have this 250 hp ( 190,000 watts) motor and it pushes the boat say 55 mph (25 m/s)
        from f=p/s then f = 190000/25 = 7600 newtons = 1700 lbs
        there would have to be 1700 lbs force on the prop and on the back of the boat, if you were to apply 1700 lbs in the small area where the motor hooks to the back of the boat doesnt seem like it would hold it
        
        Re: Homemade outboard motor using briggs 2hp - KenOhki 13:17:09 03/04/03 (10)
        
        In Reply to: Re: Homemade outboard motor using briggs 2hp posted by machnumber2 on March 03, 2003 at 10:53:32:
        
        I do not think the bearings I saw will be able to hold the shaft without some modification. Question, Are those bearings designed for taking stress from a left to right perspective on the shaft in your diagram? If they are, I would try drilling the shaft, to let the set screws actualy enter a so called set screw hole on the drive shaft, Might also look at stonger material, becuse now,, thay are more acting like shearpins then set screws.or perhaps, grind little flat stops on the shaft where the screws contact the shaft.
        Thrust bearing, Yeah that would probably make it much stronger, Might be some other way you could get around that besides drilling the shaft or grinding as I sugested. If they are cheap, Its probably the best way too go.
        In your math you mentioned it you would require all of the 2Hp of the motor to acheive the 5mph.. But isnt Prop horspower somewhat lower then actual Engien Hp on most outboards? or do I have this backwards. Also, the weight of the boat gear, motor etc dont seam to be in the equation. I supose it could be irelivant when trying to figure stress on the shaft.thrust is thrust, but does how much it is pushing affect the stress? I guess I estimate more then reli on math in most circumstances ;p And I would estimate that about 2 Hp would produce about 55 pounds of thrust, But mind you that is indead a estimate. I dont think you have told us yet how big the boat is you are using. Are you planning to pipe the exhuast underwarer?
        
        Re: Homemade outboard motor using briggs 2hp - machnumber2 14:58:00 03/04/03 (9)
        
        In Reply to: Re: Homemade outboard motor using briggs 2hp posted by KenOhki on March 04, 2003 at 13:17:09:
        
        Think I posted the first one to the wrong place..btw the bearing are not really desinged to take a sideways force, but they look pretty rugged and might handle a couple hundred pounds without too much trouble
        Making the set screw holes might work fine, these are like industrial grade bearings, the spec. sheets on them actually gets into the 1000's of pounds capacity. The reason I got them was because they were the only ones I could find. So I am thinking I will try the holes first rather than deal with a thrust bearing adding to this design. As for the math, I dunno I am just thinking back to high school physics I think. They numbers could be way off and it was kind of odd that it did not account for boat mass. The truth is, I do not have a boat lol. I plan on putting this in a garbage can full of water to test it and if I am lucky maybe I can rent a skiff to try the motor out on or maybe somebody else will test it out for me on thier boat. I figure the boat plus people (up to four) and everthing might be like 700-1000 lbs, pretty heavy for that little motor but then again it doesnt have to push it that fast. (the reason i came up with 5 mph is because that is the harbor speed limit, I want to be able to keep up with traffic so we dont get run over by some huge yacht). Piping the exhaust to the water is a great idea, the motor is going to be louder than your normal outboard. I wonder if piping it to the water would make it quiter. Are exhaust threads on these things pretty standard? I wonder if a threaded copper or plumbing pipe would screw right in where the muffler goes.
        
        Re: Homemade outboard motor using briggs 2hp - KenOhki 18:47:32 03/04/03 (8)
        
        In Reply to: Re: Homemade outboard motor using briggs 2hp posted by machnumber2 on March 04, 2003 at 14:58:00:
        
        hehe,
        well, a boat that can hold 4 with a mass close to 1000 pounds, Yeah, thats allot to ask of a home made 2 hp, but what the hell, A prodject is a prodject hehehe. Figure out a portable padlewheel device and simplify the whole process hehehe. But It appears you are aware that you are building a motor that is way underpowered for the aplication its being applied too. But it will move the boat, I am getting the impresion that you are gonna run this in a Bay?. Might not be strong enough to fight current. I was thinking this was gonna be a pond lake aplication..
        I am not sure of the threading for the muffler, But I am sure a simple adaption can be had, ANd it will definitly quiet your noise level allot. When do you think you might actualy have this together? It seams that most of the problems have been addressed?
        
        Re: Homemade outboard motor using briggs 2hp - machnumber2 16:51:35 03/05/03 (1)
        
        In Reply to: Re: Homemade outboard motor using briggs 2hp posted by KenOhki on March 04, 2003 at 18:47:32:
        
        I think everything is about a done deal and its ready to build. I am going to home depot in a bit to buy some threaded pipe, hopefully not too hard to find what I am looking for. Hopefully be welding later tonight, if all goes well I hope to have a running motor outboard in a couple of weeks or less. Btw, this harbor isnt really like a bay, its like a small city where houses back right up to the water and have a dock in the back yard, the channels being organized like streets-the water is always flat. But some places you go out into the main "streets" and meet up with larger traffic where you have to be more careful. Thanks so much for your input and advice Ken. Wish me luck, I will post photos maybe tonight of the progress.
        
        Re: Homemade outboard motor using briggs 2hp - KenOhki 19:15:47 03/05/03 (0)
        
        In Reply to: Re: Homemade outboard motor using briggs 2hp posted by machnumber2 on March 05, 2003 at 16:51:35:
        
        Thats cool, good luck with your prodject.Np on the advice. Making things do what I want them too as oposed to what they are designed to to is a hobby of mine.
        
        Re: Homemade outboard motor using briggs 2hp - outboard vision 15:04:38 03/05/03 (5)
        
        In Reply to: Re: Homemade outboard motor using briggs 2hp posted by KenOhki on March 04, 2003 at 18:47:32:
        
        Hey there guys I just wanted to chime in here. I have read all of the messages on this discussion. I have been searching for a way to make an outboard out of my old lawn mower engine. I have a 3HP briggs & stratton. I have an old flat bottom jon boat.
        
        Re: Homemade outboard motor using briggs 2hp - machnumber2 23:07:04 03/05/03 (0)
        
        In Reply to: Re: Homemade outboard motor using briggs 2hp posted by outboard vision on March 05, 2003 at 15:04:38:
        
        Sketch up what you have planned I would love to see it. Do you have a vertical or horizontal crankshaft motor to work with?
        
        Re: Homemade outboard motor using briggs 2hp - KenOhki 19:20:49 03/05/03 (3)
        
        In Reply to: Re: Homemade outboard motor using briggs 2hp posted by outboard vision on March 05, 2003 at 15:04:38:
        
        Maybe you should start a new thread if you are seriously looking to do this. Wouldnt want to get the prodjects confused by starting a new one in the middle of this one. So start a new Post from scratch, and tell me a little more. how big a boat, weather you want inboard, outboart or something Unique. How much money you have to spend, and what parts you might have on hand.
        
        Re: Homemade outboard motor using briggs 2hp - machnumber2 23:18:21 03/06/03 (2)
        
        In Reply to: Re: Homemade outboard motor using briggs 2hp posted by KenOhki on March 05, 2003 at 19:20:49:
        
        Finally started some welding tonight, a bit concerned about a few things..
        1. my welding is pretty bad hehe
        2. the pipe that I am using is galvanized something welded to steel, hopefully these things weld ok
        3. my welder is for small hobbies stuff like that so it may not be as deep as it should be.
        Anyway I was happy the see a general form start to take place. The link below shows some photos of the progress-double click the small photos to see larger ones...
        http://machnumber2.50megs.com/photos/outboard2/photos/outboard.html
        
        http://machnumber2.50megs.com/photos/outboard2/photos/outboard.html
        
        Re: Homemade outboard motor using briggs 2hp - KenOhki 12:32:51 03/07/03 (1)
        
        In Reply to: Re: Homemade outboard motor using briggs 2hp posted by machnumber2 on March 06, 2003 at 23:18:21:
        
        Looks like your on your way. I think your hobby weilder should be enough to handle it, but I am not the one to give welding advice,, I gorrilla weld myself, but my welds do seem to hold.
        From your pictures. The only warning light that went off in my head was about the motor mount.With such a small motor, it might not be a concern, However it appears to me that the weight of the motor will have a good deal of leverage against the transom. All outboards hang over the back, this is true, But they also are much closer to the transom, and in some cases even overhang into the boat some. Your mounting plate looks like it is overhanging the rear too much. The further away from the transom you mount, the more you will amplify any stress created by weight and motor thrust.. I realize its a little late for magor design changes, But I think this could be a Important design flaw you might want too address before you go much further. I bet you have a formula kicking around someplace in your head to figure how much leverage 50 pounds or so will gain at the end of a 1 foot arm. Is there any specific reason it is so far out?
        Keep us posted and good luck with it.
        
        Re: Homemade outboard motor using briggs 2hp - machnumber2 19:18:16 03/07/03 (0)
        
        In Reply to: Re: Homemade outboard motor using briggs 2hp posted by KenOhki on March 07, 2003 at 12:32:51:
        
        I think I am going to start a new post because we are getting kinding far to the side here...same name outboard motor

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