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How hard is it to remove and replace a replacement bare axle in a DD hub motor?

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    How hard is it to remove and replace a replacement bare axle in a DD hub motor?

    I have these 190mm dropout/268mm total length bare axles which I need to install in three Cromotors that I have. The Cromotors currently have axles with a 170mm dropout/248mm total length . Since I need to do this for three motors, I think it is worth it to learn to figure this out for myself (although I suppose I could hire someone to do it). Does anybody know how I would go about figuring this out?
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    Last edited by commuter ebikes; 03-02-2017, 07:47 AM.

    #2
    A hydraulic press is needed for this operation: https://www.youtube.com/watch?v=-o0B6Di2Efk and https://www.youtube.com/watch?v=-p_YB-weFm8

    In fact, that YouTube user documented the whole process:
    (1) Remove side cover bolts: https://www.youtube.com/watch?v=ELQdVW4pMU8 and https://www.youtube.com/watch?v=lYeDQS5bIw4
    (2) Removing side cover with an alternative to a bearing puller: https://www.youtube.com/watch?v=RR35HpFWt6U and https://www.youtube.com/watch?v=C2fsUYPgUAY
    (3) removing the magnets: https://www.youtube.com/watch?v=XQ2UZ9xHATY
    (4) Reassemble: https://www.youtube.com/watch?v=C0_Wq17dKxE and https://www.youtube.com/watch?v=PoBCVXY8hug (

    Note that a hydraulic press is used for installing the motor cover as well as the axle.

    If the the motor were still laced in a wheel, I don't think it would fit in the hydraulic press. Best to break down the wheel and rebuild it after the shop work.
    Last edited by commuter ebikes; 04-03-2017, 08:36 PM.

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      #3
      So now I am thinking about buying a hydraulic press so that I can remove and replace hub motor side covers and axles at home.

      There are surprisingly affordable hydraulic presses available (http://www.harborfreight.com/automot...ess-33497.html). I would just have to get a long enough stroke, large enough work area and enough pressure for working on hub motors.

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      Last edited by commuter ebikes; 03-02-2017, 11:30 AM.

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        #4
        Yes, I was just going to post that there are some reasonable hand powered presses in the price range for home builders and small shops. Before you make a purchase, you might want to double check on the price of dies and tooling for your jobs. If I recall correctly those were pricey.

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          #5
          I also emailed Vladimir S. at Zelena Vozila to get a price on three new Cromotors with the longer axles installed by the experts in Zagreb, Croatia. They would certainly do a better job than me, and I could definitely sell my 170mm dropout Cromotors on eBay. Vladimir is a joy to deal with.

          Last time I bought these same motors, each one cost me $750 delivered, or $2,250 for three. I could sell the three 170mm dropout motors (1 new, 2 used) for $1,600.

          So my budget to solve this problem myself is $650. I don't mind taking the time to do the work.
          Last edited by commuter ebikes; 03-02-2017, 11:53 AM.

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            #6
            Originally posted by funwithbikes View Post
            Yes, I was just going to post that there are some reasonable hand powered presses in the price range for home builders and small shops. Before you make a purchase, you might want to double check on the price of dies and tooling for your jobs. If I recall correctly those were pricey.
            Yes, some of this tooling and dies are shown in the YouTube videos. My friend regularly uses a cheap bearing puller (pictured) to pull off side covers, but I wonder how he gets them back on. I wonder if he uses a sledge hammer.

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            Last edited by commuter ebikes; 03-02-2017, 11:45 AM.

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              #7
              Here's a guy who don't need no stinkin' hydraulic press. A piece of metal comes flying out of the operation at the 15 second mark in the video: https://www.youtube.com/watch?v=U3t2qzQZy2g

              I wonder what the piece of metal is in the red circles in the pictures below: Click image for larger version  Name:	sdsdsa.PNG Views:	1 Size:	977.3 KB ID:	29360
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              Last edited by commuter ebikes; 03-02-2017, 12:28 PM.

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                #8
                Vladimir S. at Zelena Vozila says:

                "...I would suggest that you invest in one of these, does not have to be new :

                http://www.ebay.com/itm/PROGEN-PRO-6...EAAOSwCGVX8n4w


                sooner or later you will need to open the motor and change the bearings or axles.

                I am using the same in my workshop. Nothing special, but you can do almost everything with it
                ..."

                I was expecting him to give me a price quote on three new 190mm dropout motors, but I had mentioned in the email that I was considering installing the bare 190mm dropout axles in the 170mm Cromotors. I inquired how difficult it was. It must be pretty doable if his email response had a link to a hydraulic press and no price quote for new 190mm dropout motors.

                I went ahead and bought this one, which was just under $300, including tax and shipping: http://www.dakecorp.com/products/hyd...lic-press-b-10

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                Last edited by commuter ebikes; 03-02-2017, 02:48 PM.

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                  #9
                  I have an old screw press that is over 100 years old. It is very similar to this.

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                  Mine doesn't look as nice. It probably hasn't seen paint in 100 years either.

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                    #10
                    You have a huge hydraulic press, calfee.

                    I am really looking forward to installing these axles myself. I will make a video showing the process and post it here.

                    As soon as the press gets here, I will be ready to tackle one motor. The other two motors will be service for a year, but at least I can complete one motor!

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                      #11
                      It is not hydraulic. It has a huge threaded ram with a hand wheel. The hand wheel can do a couple of tons but to get to the twenty ton capacity there is a ratchet like a bumper jack to increase the tension.

                      Press work isn't hard but sometimes it requires a little thought. Never apply the thrust through the balls or rollers of the bearings. Save old bearings and take them apart by ripping out the bearing retainers and then save the inner and outer races. A collection of them can be used as pushing tools during installations. A couple of different sized bearing splitters are also quite handy.

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                        #12
                        Many times there is no way to take something apart without stressing the bearings because of the way the piece is designed. Looking at your axles they may be in this category. Bearings are usually based on standard sizes so replacing them is cheap insurance.

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                          #13
                          My new press arrived very quickly, and it was easy to put together.

                          i will email Zelena Vozila and ask if I should anticipate putting in new bearings when I put in the new, longer bare axle.

                          I will also ask him the part number of the bearings needed.

                          Thanks for the tips, Calfee.

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                            #14
                            I was looking at your photo again. The wires come out by that flat so you can only push one way. It also looks like there are snap ring grooves. Snap rings usually have two sides a sharp side and a rounded side. The sharp side has more holding power. This is something that most people don't know even mechanics.

                            I just watched the reassembly videos and I don't like the way it was done. Fortunately there didn't seem to be much pressure to put it together so I am sure the bearings are fine. Personally I would have pressed the bearing in the cover by pressing on the outer race and then press the cover on with a tool that would slide over the axle and press on the inner race. That would be a more difficult way but correct.........just my OCD showing................calfee

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                              #15
                              Very insightful tips, Calfee. I'm right there with ya on the OCD, believe me.

                              I own six of these motors. All four of my bikes use these, and the last two are spares. Since this is the only motor that I use, it will be worth it for me to learn how to take them apart, replace parts, and reassemble.

                              It is nearly the same motor as any QS Motor with a 50mm stator. From what I have seen, most DD hub motors seem to have the same general design. If anybody finds videos of people taking these apart, please post the links here.

                              I will post videos here of my action.

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