Announcement

Collapse

Forum rules and expectations

Hello, and welcome to the forums at the Nautilus Drydocks, formerly Sub-driver.com!

We welcome anyone with a passion for submarines and a desire to learn and share knowledge about this fascinating hobby. Use of these forums indicates your intention to abide by our code of conduct:


1. No spam. All automated messages, advertisements, and links to competitor websites will be deleted immediately.

2. Please post in relevant sub-forums only. Messages posted in the wrong topic area will be removed and placed in the correct sub-forum by moderators.

3. Respect other users. No flaming or abusing fellow forum members. Users who continue to post inflammatory, abusive comments will be deleted from the forum after or without a warning.

4. No threats or harassment of other users will be tolerated. Any instance of threatening or harassing behavior is grounds for deletion from the forums.

5. No profanity or pornography is allowed. Posts containing adult material will be deleted.

6. No re-posting of copyrighted materials or other illegal content is allowed. Any posts containing illegal content or copyrighted materials will be deleted.
See more
See less

today's work

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Dave,
    I am curious as to the KV of your outrunners? I have a pair of Graupner 500 KV outrunners, which I am installing in a Robbe U-47. I will try them direct drive initially, but I might need to go to gear reduction or belt drive if that doesn't work out. This is my first try at Brushless motors in anything but a plane. They are always so bloody fast! The 500KV Graupners are comparable to the outrunners being used by Engle in a couple comparably sized boats so fingers crossed they aren't stupid high RPMs . Up side is low current draw and longevity.
    Cheers,
    Steve

    Comment


    • Hi steve better use the engel brushless motor with 300 Kv. The graupner 500Kv is too much.




      Regards Gantu

      Comment


      • Originally posted by Stephen Vick View Post
        Dave,
        I am curious as to the KV of your outrunners? I have a pair of Graupner 500 KV outrunners, which I am installing in a Robbe U-47. I will try them direct drive initially, but I might need to go to gear reduction or belt drive if that doesn't work out. This is my first try at Brushless motors in anything but a plane. They are always so bloody fast! The 500KV Graupners are comparable to the outrunners being used by Engle in a couple comparably sized boats so fingers crossed they aren't stupid high RPMs . Up side is low current draw and longevity.
        Cheers,
        Steve
        Temper my comments by knowing that I'm new to the black-arts of brushless motors.

        So far my only practical experience is with the D3548-6. Rated to run off a 11.1 - 18.5V source this motor will yank up to 60A stalled. This outrunner is 790 KV, which I understand means it has a relatively high torque at a lower than 'normal' speed. I have bare-fisted this thing at 11.1- volts and must say it has considerably more ass than a brushed 555 motor!

        That said, I would assume you're 500 KV motor is even better in the torque department. For direct drive the old rule-of-thumb for brushed motors was that if the propeller diameter was not too much more than the can diameter, then it was OK to go direct-drive without over-loading the motor. With these more efficient brushless units we can assume an acceptable motor:propeller diameter ratio to be 1.5:1.

        What's your Robbe U-47 propeller diameter? I assume its close to your Graupner motors diameter, so direct-drive should be OK for you installation (assuming a dedicated motor per propeller).

        The big practical fly-in-the-ointment with outrunners is the need to suspend the motor by its mounting spider. As demonstrated here:





        Remember the gear-splitter we came up with for your little TRUTTA? I've done pretty much the same thing to get two shaft output from the single D3548-6 motor:















        Andy!!! Help us out here, pal.

        David
        New-to-this-****!
        Last edited by He Who Shall Not Be Named; 02-21-2020, 04:08 PM.
        "... well, that takes care of Jorgenson's theory!"

        Comment


        • Awesome trip down memory lane Dave ! I just did some shopping on McMaster Carr and think I have a pretty fair 2.5 : 1 ratio belt drive being shipped to me... I am expecting a lot more torque from the little 500KV's than from the stock 600 brushed motors. My only concern is the motor RPM's, but I think the reduction will be sufficient. Its all experimentation really. A dash of experience and a spoonful of guesswork... I'm totally gonna steal your mounting stud method!
          Cheers,
          Steve

          Comment


          • Originally posted by Stephen Vick View Post
            Awesome trip down memory lane Dave ! I just did some shopping on McMaster Carr and think I have a pretty fair 2.5 : 1 ratio belt drive being shipped to me... I am expecting a lot more torque from the little 500KV's than from the stock 600 brushed motors. My only concern is the motor RPM's, but I think the reduction will be sufficient. Its all experimentation really. A dash of experience and a spoonful of guesswork... I'm totally gonna steal your mounting stud method!
            Cheers,
            Steve
            Yeah! Back when photography was chemically based. Only visuals I have from those days are scratched and faded emulsions on 'film'. Mid-80's was when we were all terrorizing Lake Trashmore?

            Don't think you'll need to up the torque with a reduction unit, Stephen. But, as you so correctly observed it's all a good helping of guesswork.

            Too late to rip me off on the studs -- I stole that mounting arrangement years back from one of my betters. Nothing new under the sun, only varied applications of the same tricks.

            Loved the mounts GANTU illustrated. That guy is a wealth of good stuff! I would employ the same trick if I ever figure out how to beak the set-screws that secure the motor shaft from the rotating bell without turning everything into slag.

            David
            "... well, that takes care of Jorgenson's theory!"

            Comment



            • Sheet metal work today.













              "... well, that takes care of Jorgenson's theory!"

              Comment


              • I like sheet metal. It really sets your Sub-Driver apart.
                If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

                Comment


                • Originally posted by trout View Post
                  I like sheet metal. It really sets your Sub-Driver apart.
                  Thanks, Tom. I've always been fascinated by what can be done with sheet-metal. Particularly today, when you watch how their working stainless steel plate into compound and simple curves to make Elon Musk's Starships.

                  Whenever it comes time to do sheet-metal work and I settle into the routine, I'm reminded of those few happy times I had in high-school -- shop class, where I was introduced to mechanical-drawing, machine-shop, welding-shop, wood-shop, and metal-shop. Back when such classes were routine for boys, but today replaced by black-history-month (every frig'n month of the school year) and other completely useless and sometimes counter-productive drivel mandated by screaming Liberals who reside in the Swampland of Federal agencies run by thieves, Congress Critters, cronies, and lobbyists.

                  David
                  "... well, that takes care of Jorgenson's theory!"

                  Comment

















                  • "... well, that takes care of Jorgenson's theory!"

                    Comment









                    • "... well, that takes care of Jorgenson's theory!"

                      Comment















                      • "... well, that takes care of Jorgenson's theory!"

                        Comment









                        • "... well, that takes care of Jorgenson's theory!"

                          Comment


                          • Loved the mounts GANTU illustrated. That guy is a wealth of good stuff! I would employ the same trick if I ever figure out how to beak the set-screws that secure the motor shaft from the rotating bell without turning everything into slag.

                            Like this with this tool allen key













                            Regards Gantu

                            Comment


                            • The video I watched where the motor shaft was reversed; stressed using only high quality allen / hex wrenches. He stated anything else would round out the set screws. He did mention maybe heating
                              the set screws first. No harbor freight allen wrenches allowed.

                              Comment


                              • Originally posted by Scott T View Post
                                The video I watched where the motor shaft was reversed; stressed using only high quality allen / hex wrenches. He stated anything else would round out the set screws. He did mention maybe heating
                                the set screws first. No harbor freight allen wrenches allowed.
                                I tried the heat-trick. No soap. I've come to terms with the need to work with the motor shaft as-is.







                                David
                                "... well, that takes care of Jorgenson's theory!"

                                Comment

                                Working...
                                X