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Want to modify steel Surly Big Dummy frame for Bafang Ultra

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    Want to modify steel Surly Big Dummy frame for Bafang Ultra

    I'm new to this forum. I've been checking out the Luna Cycle page with an eye towards converting my Surly Big Dummy to electric. I believe the stoutest and strongest option available while having a smooth PAS system (I'm only interested in PAS) would be the Bafang Ultra Ludicrous edition (I want speed AND hill climbing power). Is it possible for a frame builder to cut my steel frame and weld in the aluminum mounting plate for this motor? Or do they need to fabricate something from steel to work?

    #2
    Originally posted by Cargo Ken View Post
    I'm new to this forum. I've been checking out the Luna Cycle page with an eye towards converting my Surly Big Dummy to electric. I believe the stoutest and strongest option available while having a smooth PAS system (I'm only interested in PAS) would be the Bafang Ultra Ludicrous edition (I want speed AND hill climbing power). Is it possible for a frame builder to cut my steel frame and weld in the aluminum mounting plate for this motor? Or do they need to fabricate something from steel to work?
    Very very hard to bond aluminum. The bracket will have to be Steel.

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      #3
      So...how hard is it to build a steel bracket for the Utra to weld to the tubes of my Big Dummy? Can any frame builder do it?

      Comment


        #4
        I Googled some pictures of this motor and mount. This is what I got:

        Click image for larger version  Name:	50723_319703d3_148993670382_450_300.jpg Views:	1 Size:	13.3 KB ID:	57938Click image for larger version  Name:	BP551xq.jpg Views:	1 Size:	161.7 KB ID:	57939Click image for larger version  Name:	flx-blade-bafang-ultra-1000-watt-mid-drive-motor.jpg Views:	1 Size:	899.9 KB ID:	57940

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          #5

          Continued:
          Click image for larger version  Name:	img_20170316_154627805_hdr.jpg Views:	1 Size:	1.10 MB ID:	57943Click image for larger version  Name:	img_20170316_154618479.jpg Views:	1 Size:	1.27 MB ID:	57944

          Click image for larger version  Name:	ultra.png Views:	1 Size:	86.6 KB ID:	57942

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            #6
            This https://electricbike-blog.com/2017/0...ing-mid-drive/ does say that it has a very "thick cast aluminum case". Does that mean the case to the motor or the mounting bracket?

            Hopefully someone from Luna will chime in and clarify the whether the mounting bracket is steel or aluminum. If the mounting bracket is steel, that is so much easier.

            Some framebuilders would be willing to notch the tubes on a frame that is already built, as one would do when replacing a damaged BB.

            All the frame fixtures (jigs) that I have ever seen are for the more common BBs. I would imagine that the framebuilder would have to modify the frame fixture at the point where the BB clamps in to the jig.

            If it is an aluminum mounting bracket, you could find a custom frame builder that works with aluminum (uncommon in the US) and give him the mount and motor. I imagine that the frame would cost you about $1650 plus shipping. The good news is that you could choose all of the specs (e.g. wheelbase, head tube diameter, etc.) for the frame, and the frame would fit you perfectly.

            If it is a steel mounting bracket, most framebuilders could build you a custom steel frame around the motor and bracket, although I would like to see how they clamp the BB in the frame fixture. Expect to pay at least $1,500 plus shipping, but a custom frame is a wonderful start to a project!

            Also, find out what type of aluminum (6061?) or steel (4130?) the bracket is made of so that the framebuilder can choose the proper filler material.
            Last edited by commuter ebikes; 02-12-2018, 10:24 PM.

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              #7
              You might want to consider a Stoke Monkey. It would be more cost effective. They also have a lot of performance. http://www.ebikes.ca/classic-stokemonkey-kit.html

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                #8
                Don't cut that beautiful steel surly frame. You would be super happy with a BBSHD on that frame with or without Ludicrous upgrade. PAS is very good and very adjustable with open source software.

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                  #9
                  Are all of these "integrated motor frame mounts" (for the lack of a better term) proprietary to their motor manufacturer? As in, no standard has been defined?
                  BBSHD / BBS02 IGH Builds: Nexus / Alfine 8: 1 2 3 4 5 6, Rohloff: 1

                  Comment


                  • moarpower
                    moarpower commented
                    Editing a comment
                    Do you mean Yamaha, Bosch, and Bafang Ultra mid drives?

                  • ncmired
                    ncmired commented
                    Editing a comment
                    Yep - "them ones" ;-)

                    Just like swapping brakes, the drive train, ergonomics, etc. A good bicycle frame (especially a custom one) should not be just another disposable.
                    Last edited by ncmired; 02-17-2018, 09:04 AM.

                  #10
                  Originally posted by ncrkd View Post
                  Are all of these "integrated motor frame mounts" (for the lack of a better term) proprietary to their motor manufacturer? As in, no standard has been defined?
                  From what I can tell, not only are they proprietary to each manufacturer, they are also different among different models from the same manufacturer. Bafang has different models frame mount models available, and each one has it's own shape mounting plate, they are not interchangeable among models.

                  Comment


                    #11
                    We never found out if this mounting plate is steel or aluminum. Does anybody know what material this is? It is listed for sale for $40 here: https://lunacycle.com/bafang-ultra-m...ike-mid-drive/

                    Also seen here: http://www.bafang-e.com/en/component...s/fp-g510.html and here http://www.bafang-e.com/en/component...n-parts-a.html

                    This post says that it is aluminum: https://endless-sphere.com/forums/vi...p?f=28&t=91210

                    Here is another picture. By the looks of the weld beads (and material!), it is aluminum.

                    Click image for larger version  Name:	GOPR2270_1.JPG Views:	1 Size:	69.5 KB ID:	58276
                    Last edited by commuter ebikes; 02-17-2018, 09:41 PM.

                    Comment


                      #12
                      I put a 52 volt BBSHD in my big fat dummy and I love it. If you got money to burn then what you are wanting to do would be very nice. I also have no throttle and the fastest I’ve gotten is 24 mph. I generally run at 200 watts Pedal assist except for one steep hill on by 27 mile commute that I run at 600 watts. My battery is 14s8p w/3500mah cells but limited by a 30 amp bms so I may be missing out on some extra power there. I did also consider the same thing you are but didn’t want to wait for the fabrication process after I figured out the pre-dabbed bracket was aluminum. Best of luck, either way you’re going to have a great time.

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                        #13
                        Hi Manbikepig, do you have any photos I could see of your Big Dummy motor set up please?

                        Comment


                          #14
                          If you don't already own the bike and it doesn't have to be a Fat Dummy it may be worth a call to your local bike shop and ask about a deal on a Big Easy. As of a few weeks ago (November 2020) I heard they still have 2020 models in stock in all sizes and are making deals to get rid of them. I think regular MSRP was a little high and you could have done better buying the Big Dummy and a BBSHD but if they are knocking $1000 or more off the price to get rid of them may be a tempting way to go if you don't need the ultimate power and just want something that works. I haven't seen it but I have heard the dual battery option is pretty neat and slick. If you like to tinker and need all the possible power you can get then a BBSHD is still an option. I know the regular Dummy doesn't have any spacing or chain ring or line issues. Pretty sure the Fat Dummy is pretty easy to do too as far as clearances.

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