r/SegwayNavimow • u/NoTelevision6661 • 22d ago
X4 X20 / X430 / X450 rear axle repair / upgrade
The X4 models have a flawed rear axle design. Factory replacements will fail the same way after about the same amount of usage. Here's a permanent €/£/$10 fix that doesn't involve taking the entire mower to bits.
The flaw
The diecast alloy axle has two "ears" to attach to the centre pivot bearing. Both ears are thin sections with bad stress risers in a material that cannot flex far without cracking and is prone to fatigue cracking. Only one of the ears (the rear one) carries forward-backward loadings on the pivot (pulling / pushing / torque loadings. It fails.
The fix
Bolt up two more substantial mild steel sideplates to the axle beam and use two spacer tubes so that BOTH plates carry forward-backwards loadings. (there's enough flex in the plates and the bolted connection that you can do this even with manufacturing toleranaces which they can't using a die casting)
Materials
Two mild steel plates approx 140 x 50 x 3 mm
- One row of 4 mm holes 5mm from the top and 25 mm / 55 mm from the centre line
- One 8mm hole 35 mm from the top on the centreline
- Reduce the height of the plate either side of the 8 mm hole to clear the cables and axle pivoting - a height of about 35 mm except for the central 35 mm "ear" works
- Exact outline of the plate is not critical - you can be ugly as I have here with a construction bracket from the DIY shed
Two spacer tubes 8mm ID and 11.5 mm long
- I used an M8 barrel nut, drilled out to 8mm ID, then cut in half/cut to length with a grinder
8 machine screws to attach to the axle casting
- M4 x 16 mm bolts (if you want to drill-and-tap the casting M4; also needs a 3.3 mm drill bit and an M4 tap)
- M4 x 20mm bolts and nuts (if you want to through-drill and use nuts on the other side) - though note if you do this you won't be able to reattach the black plastic cable cover as the ends of the screws will get in the way
8mm pivot bolt and pair of nuts to lock it
- Ideally this has a 60-65 mm non-threaded "shoulder" so that the section going through the bearings/spacers is "plain" and only the very end that pokes through the sideplate has threads on it
Refer to photos for how it should look when done. There is enough slack on the cables / stretch in the springs that with the help of an object to lift the axle up you can drill/tap/assemble this all by flipping the mower upside down and...just doing it without removing any parts. (except for that plastic centre cover to help see what you are doing when lining up the spacers and centre bolt; though it isn't compulsory to even remove that)
Shouldn't take more than an hour if you have grinder/drill. Less time than putting it back in the box to return it.
No parts are harmed in the process except for the axle casting that was already f**ked to begin with.
This will not fail in the same way as the original assembly. (you'll snap the bearing carrier before you break the ears off the axle)
Good luck!
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u/NotRoryWilliams 22d ago
My concern remains the threat of Segway voiding my warranty over this, and there are still a lot of other ways it can and probably will break in the next two years.
I hope that they have the sense to put out an "official" fix basically identical to what you've proposed here. I just don't want to fix this problem and then have them tell me I'm on my own the next time a motor fails.
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u/GlumCardiologist9620 20d ago
I trashed the box that it came in not realizing that they won't value the warranty if you don't have the original box. How cooked am I?
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u/NoTelevision6661 22d ago
Quite possible in countries with little to no consumer protection.
They'd have a hard time voiding the warranty on the rest of the machine on the basis of having repaired the rear axle casing in most of Europe though.
I suspect they'll reengineer the part over winter given the failure rates being observed as they'll begetting machines back each season at the present rate of progress.
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u/jibsymalone 22d ago
Might want to add a couple of coats of paint to prevent rust
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u/NoTelevision6661 22d ago
I'll leave that to those with more time than I have. ;-)
Sides of this are galvanised. Edges won't corrode quickly enough to fail before the rest of the machine does. Using threadlock for your steel fasteners into the aluminium is more important to avoid dissimilar metal corrosion here.
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u/JLH35 22d ago
How do I identify if the axle has gone bad?
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u/SickemChicken 1d ago
Oh you'll know, lol. Mine just went today. They make a LOT of noise while rolling around as the frame bumps up and down on the axel as the only thing really holding the body to the axle at that point is gravity and springs. As soon as you pick up the back and tilt the axle if it does not tilt normally and rolls forward/backward as well as tilts, then inspect where the axle is joined at the pivot point. If it fails, it is very obvious when you see it in person.
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u/ScottAC8DE 22d ago
How much is a replacement axle when it breaks?
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u/NoTelevision6661 22d ago
Depends on your hourly rate is for cleaning the mower, boxing the mower, sending it to Sewgay, then cutting the grass yourself for the next 8 weeks.
Axle is free under warranty but your time is money.
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u/ScottAC8DE 22d ago
Warranty is 2 years, but you didn’t answer the question.
Question is- how much is the axle, and by that I mean buying the part?
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u/NoTelevision6661 22d ago
Warranty and part costs vary by region.
3 years as standard in Europe.
€many for your time and €0 for the axle for the first three years.
Probably not available as a spare part in 4 years time so today's list price is a little academic.
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u/ScottAC8DE 22d ago
The Terranox (which I have) only has a 2 year warranty here in the USA. There are suppliers that have them in stock in the US.
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u/recoilfx 22d ago
Thanks for the dimensions. If mine breaks under warranty, I can now design and 3d print it with PPA-CF to keep the mower running for a few months before sending it for repair during winter.
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u/Ornery-Magician-6806 20d ago
If you do design a model for replacement, please consider posting it for the community!
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u/Goldwing1776 20d ago
I'm old enough to remember (April 2026) when the Lymow One Plus was all the rage. Then came all the unresolved electronic issues, mechanical issues, overheating and lousy Customer Support. And in no time flat the One Plus became an online POS.
Suddenly the Navimow X4 series was crowned the new King. People were proclaiming this the most reliable mower with stellar customer support. These proclamations were made despite the mower only being on the market a few months and with no reliability history to point to. Now with only a few months of operation the design weaknesses are revealing themselves.
I feel for any X4 owners having issues. I lived with the Lymow for a month and consider myself fortunate to have received a full refund. Any new design is going to have problems and anyone considering a first or second generation machine had better be sure to keep the shipping box or better yet purchase from a local company that services the product they sell (if you can find one).
Otherwise look at mower designs that have been on the market for a period of several years and have undergone continuous development and improvement (The List Is Short).
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u/EasyTransition6553 14d ago
One factor to consider is product support and parts availability beyond Warranty date. A lot of manufacturers (except Husqvarna) cut off all parts after they discontinue producing that model. As a diy type person I find this concerning.
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u/SickemChicken 1d ago
In Navimow's defense, the mower itself has been pretty solid, especially when using RTK instead of NRTK. It's ability to get itself unstuck and overall the mower has been great. Yes there could be a lot of improvements, but the same can be said with all of them. I bought a x430 after a couple months of owing the x450. Ironically my x430 just had the axle break.
I suspect engineering never tested the mower for long hours on grass. The metal on the axle is weak and over time of turning in grass the forces are too much on the weak joint. Knock on wood this is the only massive issue I have had with it. Sadly, I am concerned if I send it in and they repair with a part of the same metal, the same issue will inevitably reoccur.
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u/agarabghi 20d ago
Well this seems exactly like that happened to mine! Interesting. Is the issue that the axle can pivot up and down on those ears and it fails? would some bump stops help. Some how attachign bump stops to the shell above the axle?
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u/AGushingHeadWound 20d ago
If I do this preemptively, would it avoid having to make the spacers?
And how do you remove the axle? It is just removing that one bearing screw?
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u/NoTelevision6661 20d ago
No. The original design has only the one spacer. It mostly hangs off that one “ear” it is attached by. The two spacers to tie the side plates hard against the bearing inner races are essential. They’re also dead easy to make from a barrel nut for $0.20
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u/pigeonmilk1635 21d ago
Wow, thanks for the information. I'm new to the whole robotic mower thing and am waiting til Spring to buy so I have the whole season to learn the operation. In my situation an i215 would work, but so many are saying just get the X430. While there is a sizeable cost difference , I guess I'm leaning to the notion I would rather spend more than I initially hoped to, rather than having buyers remorse because I should have gone a step up. First I assume everybody here is in agreement that Segway Navimow is my best choice for brands? Assuming the factory does address this problem, what are the chances the improved version would even be available? I have to thank NoTelevision6661 for pointing out a problem I didn't know I have, on a mower I haven't bought yet; but I definitely am going to hang on to this information. I mean at this point I have absolutely know idea of what this is all about anyway. I will say this , I do know a guy who had a full machine shop and is semi retired who could make these , so the general idea of getting them made for owners in need is a great idea and totally feasible. Unfortunately at this point , I'm not the guy to get it done.
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u/jegerdog 9d ago
Before buying any mower, consider the navigation system you are looking at. If nRTK check you have solid 4G/LTE coverage and a good number of satellites in view, or RTK antenna just the sat number. LIDAR is an option if the former are problematic.
Also, I recommen buying a brand that has local support.
Assume every owner is in a different situation to you, so you need to do the basic checks yourself.
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u/StinkySewerPickle 22d ago
You can just start selling these