Ideas for Home Made Mud Motor

Discussion in 'Mud Motors' started by Flutterin'_Wings, Oct 8, 2008.

  1. Flutterin'_Wings

    Flutterin'_Wings Elite Refuge Member

    Messages:
    4,451
    Joined:
    May 11, 2003
    Location:
    Mankato, MN
    I am thinking of making either a longtail or shortshaft mud motor for my final project here in college for Machining. I currently own a 2000 24 horse beavertail longtail and it has its advantages and disadvantages. I have a 16'x60 v haul fiberglass smooth bottom with one big keel. I put pods on the back and its really a nice boat but it could use a little more hp.

    I dont like how long of stretch the CRS shaft is between the two bearings. I think with all the tourqe that has to have some torsional affects between the two. Especailly when running in shallow waters where some things knock the prop out of the water and it zings. Has anyone thought of using a more rigid material such as stainless or a grade of tool steel for the shaft?

    For a short shaft, whats the dis/advantages of a horozontal shafted motor with a belt and a vertial shafted motor?

    Also, whos the guy from MN who built his own motor, I think from waseca?

    -Josh
     
  2. Turn4fun

    Turn4fun Senior Refuge Member

    Messages:
    181
    Joined:
    Dec 3, 2006
    Location:
    mo
    I don't know what the commercially built mud motors use, but in all of the homebuilt motors I've made (even the little weed wacker longtails) I used 316 stainless for the drive shafts.
     
  3. cajunwannabe

    cajunwannabe Senior Refuge Member

    Messages:
    194
    Joined:
    Nov 12, 2005
    Location:
    Wishing I was in SE La.
    Would you consider a short shaft horizontal mud motor? 1 inch diameter shaft straight out the back of a 20 something motor? I have some ideas and have seen them run. Let me know if you are interested. This isn't a "production" motor.

    Isn't Prodrive the only Vertical shaft motor...gear driven. All others are Horizontal shaft...belt driven. Dis / Advantages I see with a surface drives they'll get you where you want to go very fast and get you 10 x's as stuck, that and NO belt driven motors have full power reverse.
     
  4. gmag10

    gmag10 Senior Refuge Member

    Messages:
    180
    Joined:
    May 20, 2003
    Location:
    Faribault, Mn
    At one time, I think many longtail manufacturers were using 4140 and plating it. This material will give you a 125-130 KSI tensile strength and will take the abuse of the shock loads that a mud motor shaft will see. But...... I would recommend using 17-4 H1150 Stainless steel. This will be a bit more expensive, but will give you corrosion resistance and a tensile strength around 170 KSI. You will not break that shaft. I have made 2 motors and have used this material both times. It will not cut as nice as other materials, but it can be machined. The other thing that this material has going for it, is the fact that it is already centerless ground so it will be nice and round and will have a tolerance of + 0" / -.002", I think. Go to your local Fastenal store and they will be able to order it for you. Make sure you get H1150, because there have been some studies that show in the annealed state it will develop micro-cracks with time. I used annealed material in my first motor and it is still going strong after 5 years.

    Mag 10
     
  5. gmag10

    gmag10 Senior Refuge Member

    Messages:
    180
    Joined:
    May 20, 2003
    Location:
    Faribault, Mn
    Shoot me a PM and I will give you my contact info.
     
  6. Flutterin'_Wings

    Flutterin'_Wings Elite Refuge Member

    Messages:
    4,451
    Joined:
    May 11, 2003
    Location:
    Mankato, MN
    I am 99% sure the shaft comming out of my beavertail was CRS.

    When I go with stainless I would plan on buying a couple extra inches and do the threading on the lathe first. I am sure it will be a fun one, but a fresh carbide and light passes should do it.

    The thing I didnt like about the CRS either was when i replaced my bearings and seals, the bearings actually scored the shaft .005-.010 dp. lopsided making me think the shaft was bent which isnt that hard to do with CRS. I think I would run 1" dia. instead of 3/4" shaft also.

    I was thinking of a shorter shaft to make it more rigid cajun, but wouldnt you need so much length to get the prop angle right so your not digging too much?

    I want to run a motor in the area of 30-35.

    I also dont like the surface drives because they are LOUD, and a lot of electronic tilt which is nice for cruising, but as mentioned they arent that great when its real shallow or struck. at least with the longtails, you can put the prop wherever.

    thanks guys,
    Josh
     
  7. aka quackshot

    aka quackshot Senior Refuge Member

    Messages:
    492
    Joined:
    Jun 26, 2005
    Location:
    sumter s.c.
    I have been using 4140 unplated for years with no problems, but I agree with gmag on the 17-4 SS If you want to pay the extra $$$$
     
  8. gmag10

    gmag10 Senior Refuge Member

    Messages:
    180
    Joined:
    May 20, 2003
    Location:
    Faribault, Mn
    The cold rolled material is much softer than the bearings and will deform before the bearing does. 17-4 is expensive, but is not a huge cost when you compare it to the total cost of the project. I think the 17-4 for my longtail was about $40. ~60" shaft

    Either motor design will have it's benefits. A short tail should be no louder than a longtail with the same engine. You may get a bit more prop noise because it is a surface piercing prop, but it will be minimal. I put a simple hand trim on my motor and it works pretty well. There is no need for electric T/T if the motor is half way balanced.

    The more angle you have on your motor, the more thrust you lose.

    Mag10

    PM back at you.
     
  9. cajunwannabe

    cajunwannabe Senior Refuge Member

    Messages:
    194
    Joined:
    Nov 12, 2005
    Location:
    Wishing I was in SE La.
    If you can hold onto it the straight short shaft motor I have seen can even run across a sand flat. I don't think it's louder than any other mudmotor. The motor I've seen was a Honda 24 hp. My buddy had a 36 inch shaft and just changed it to a 40 inch. I think it has an 11 inch prop and over double cup...for biting the sand. If you have the knowledge and are looking to build / experiment with something along these lines let me know. It's the only motor I know that can go where others absolutely CAN'T.

    GMAG10, have you ever seen a short straight shaft motor? No u joint, but a coupling between the motor and the shaft. You get 100% out the back of the engine that way. What are your thoughts?
     
  10. extra mud

    extra mud Elite Refuge Member

    Messages:
    4,341
    Joined:
    Jul 7, 2003
    Location:
    Sussex , Wisconsin

    Sorry, a surface drive will walk all over any long tail. Hands down.
     

Share This Page