[Liebregts] is working on a trike design, and needed a pair of wheels to go up front. Regular bicycle wheels wouldn’t do, as they’re not designed to work with a single-sided support. They also wanted to be able to mount disc brakes. Thus, they set about building a set of custom wheels to do the job.
The build began with a regular set of 20″ bike wheel rims with all the spokes taken out. A ring of steel rebar welded on the inner perimeter gave the rims more strength. A set of hubs and axles were then fabbed up with a welder and lathe, with provisions for bolting on disc brake components. Lengths of rebar were then welded in as non-adjustable spokes. Next, it was time for a coat of paint. Finally [Liebregts] mounted the tires and brakes, and called the job done.
Obviously, it is possible to buy wheels specifically for trike builds. However, [Liebregts] found it difficult to find exactly what they wanted, particularly where the disc brake option was concerned. The best option was a custom build. The resulting wheels are obviously much heavier than traditional bike wheels, but they’re also likely a fair bit stronger, too. If you need to weigh down a tarpaulin, for example, these wheels might just do the trick.
We’ve seen some other crazy wheels on trikes before, too! Oh, and who says wheels need to be a full circle, anyway? Creativity will never cease to amaze!
Bike spokes are under tension. Steel is very good under tension. These spokes are under compression / torsion. So I’m not sure about them being ‘much stronger’…
Depending on the order of welding, they could be in tension. Welds contract quite a bit as they cool.
So I think if it was welded in criss-cross pattern balanced around the wheel, it could pull a tension on the bars.
Huh. My guess would be at the hubs. Especially when breaking. Normal spokes are hinged at top/bottom so they’re under pure tension. These will try to hinge on the weld. At the hub it takes a lot more rotation to put enough tension on them to resist the breaking force. So the welds will bend quite a lot.
You mean braking so hard that they break?
Yeah, sorry. I meant brake. Not a native speaker.
Rough analysis (These are quick numbers done in my head. If you can do better, please do):
18 spokes 6mm (#2, US) rebar– #2 rebar is good for about 1T in tension (yield), and about 2T in compression, as long as it isn’t a slender column. These spokes are about 220mm long, giving a slenderness ration of a bit less than 40:1, so these should be ok in that respect, as well, in particular at the end constraints at rigid, not free or pinned.
The fitup, presuming the welds are good and there are no significant stress risers, gives bending moments as well as shear at the hub joints, but bending is not significant at the rim. These moments are unknown without knowing the torque applied, but given the stiffness of steel, the good fatigue limit for steels, and the large total weld area, I would guess that this will not fail in a human powered application.
I would have concern about the bending moment on the 14mm threaded rod, due to the approx 11mm root diameter and the stress risers at the thread root. Figuring, roughly, 150Kg (1500N) for machine and rider hitting, and all of that on one wheel worst case (bump, for example), 50mm (estimated) from the axle fixture point to the centerline of the tyre, there will be about 50MPa with no side loading on the wheel, or maybe 1/4 the yield. Side loading will significantly increase this. I would expect a pretty limited fatigue life here.
No hubs with single-sided support? They never heard of Cannondale Lefty.
BMX wheels and hubs have more than enough strength to work one-sided. It’s not like this isn’t a solved problem in bike construction.
Both my stroller and bike trailer for the kiddos have quick release one sided hub mount things.
Never heard of a Recumbent trike, there are tonnes of them.
There do exist single-sided bike wheels with disc brakes. See e.g. https://www.cannondale.com/en-eu/gear/components/suspension
I would trust them more than these DIY ones since they are centered and balanced and in the light of the photos for rough terrain, too.
There are also purpose made wheels for this, look up HP Velotechnik or any of the recumbents trike manufacturers.
This really wasn’t needed.
By the look of it, they aren’t driven, so bugger all torsion except under braking loads….. Prolly fairly robust if not somwhat agricultural.
Braking loads are the most significant torsion load of modern bicycle wheels. The brakes can generate far more force than your legs or any moderately sized motor.
I think if I was going to weld a bike wheel to my needs I’d just ditch the spokes all together and create shallow cones in sheet metal. Lighter and stronger to the forces in play than this rebar I expect, more aerodynamic too.
Still looks like a pretty good job to me, aught to be rather overkill for the loads in play if those welds have actually penetrated properly.
Good luck with that. Especially in a garage shop
If you know how to work sheet metal you really don’t need much in the way of tools, Ron Covell really shows how little you need to work sheet metal in some of his youtube series for instance.
I’m not saying I’m nearly as skilled as he is to find it pretty trivial, but from learning the techniques and thinking processes required from folks like him I’m convinced I could give it a good go. Maybe I ruin the first try, even the second, but so what the result in the end is worth it.
Used plow disc would make this super easy. And the used ones are fairly light.
Looks deadly. If a normal spoke breaks, nobody dies. If one of these spokes fails, you get impaled by rebar. This is not only unnecessary in solving the issue, it adds significant risk.
given that it’s on the outside of the vehicle it should be a distance away when it does let go. however, rebar is a terrible choice for this application, it is very brittle, will break at any stress, rather than flex which is what you want for safety. it’s about the same price as regular mild steel so there’s no excuse here.
Rebar isn’t generally brittle. It it were, it would not do its job. Most grades are meant to be formed (bent), and most grades are readily weldable, though if they are to be welded a grade specifically designated for welding should be used.
This is, of course, presuming that the supplier provided material that actually meets the spec. If not, I wouldn’t use it to reinforce a footing for a doghouse.
If either breaks you almost certainly don’t die, a wider hole might scar much worse but wide or thin what matters is what it ends up penetrating… Which in both cases is likely to be absolutely nothing of great consequence – not saying it can’t happen, as really bad luck can always happen but the odds of either really being driven into a person far enough to reach something that really matters are low, as most of the stuff that needs a surgical team and operating theater in improbably short order is quite a long way under the skin.
The bigger mass of the rebar gives it some more interia, but also lots more surface area for drag and to spread the energy it carries across more skin and shed that inertia – all in all likely to cause similarly severe (which is to say not very) injury. Wouldn’t want to be on the wrong side of either, but there are so many really more common and severe dangers out there…
On a bicycle? This ain’t gonna break. Maybe on a motorbike
seems to me the ‘right answer’ was to just make custom hubs and otherwise build a typical bicycle wheel with typical spokes etc
But that is the sensible thing to do! Creating a wheel that doesn’t weigh a ton. How boring.
I do agree though I can’t quite see the point of this, seems like a fairly backwards method. But it should work well enough for the intended use, and they probably had these parts in stock.
Making your own hub is a PITA. It requires a pretty careful setup so the bearings at both sides are colinear with each other so the hub axle fits through, and then you have to drill a ton of evenly spaced holes for the spokes. (And machine a conic surface on the flanges so the spokes don’t bend over them, but that’s easy.)
The solution is available off the shelf: Cannondale Lefty front hubs. They’re designed for disc brakes and for single-sided support. But they are Not Cheap, so I understand the reasons for this.
Though, I think I’d be more likely to use a high strength steel axle and an older high-flange hub and machine a disc brake adapter to fit into the high flange hub.
Getting DIY spoked wheels true enough to be comfortably rideable would be a significant challenge. It sucks riding on out of round wheels, and 1/3 of the point of spoked wheels is that they can be retrued to nearly perfect roundness whenever you want.
They do this all day long with wheelchair hubs. It’s not difficult and trike makers have been churning out disc and hub breaks for over a decade. I experienced more issues with the frame than I ever did with the wheels on mine over thousands of miles. These are just heavy and silly.
What custom hubs? Regular lefty hubs would have worked just fine.
> Regular bicycle wheels wouldn’t do, as they’re not designed to work with a single-sided support. They also wanted to be able to mount disc brakes
It appears [Liebregts] is not familiar with the Cannondale Lefty fork system which is both single-sided and has disc brakes.
https://www.cannondale.com/en-us/gear/components/suspension/lefty-ocho
Not only Cannondale’s Lefty, but every recumbent trike made (and non recumbent trikes as well) has support from only 1 side using relatively ordinary bicycle wheels. And those generally include disc brakes as well.
They went way overweight with the rebar, gained essentially no strength (and possibly lost some with the welding joints – they welded rebar to the thin sheet metal of the rim, thus weakening the sheet metal). The wheels will no longer stand up well to flexing.
Whoever designed this didn’t understand the engineering behind bicycle tires.
the bicycle is what one might call a mature technology, by which i mean people keep trying to reinvent things bicycle mechanics and builders have known how to do (or, alternatively, why not to bother) for years or decades already. in this case, as tron noted, Cannondale’s Lefty system. it’s not that it doesn’t work — it works well enough — it’s that it proves you don’t need rebar spokes to do it.
There are hubs available with 15mm hollow shaft usually with aluminum axels. I used these and bought matching spikes and made 20″ wheels for my cargo bike from them works fine for the last 2 years now. I used 15mm steel axis single sided no problem so far. (Shimano XT VR-Nabe HB-M8110-B Disc Center Lock 15 mm).
The 14mm threaded root is the weak point und will probably break. My first try was something like this and did not work.
Didn’t balance the wheels?
I was about to say—somebody is going to need about seventeen full strips of those little lead weights
This is interesting. Bike wheels do not usually get balanced like car wheels/tires do. Their mass isn’t enough to matter. But what they absolutely need is to be trued so they they are round and concentric, and usually symmetric left-right although most modern rear hubs are asymmetric. The mass of there monsters, though? May need to be dynamically balanced and since they are welded up there is no way to adjust concentricity either. So a disaster all around. Oops.
I’ve seen quite a bit of redneck engineering in my life, and there are some times where a custom part made by hand from scraps is perfectly sufficient even if it’s not built to the same level as a manufactured part. That’s just never the case with wheels.
Things you should never skimp on when building a custom include: drivetrain, frame, brakes, wheels, tires, electrical. If you think you’re going to build any of those yourself you better have the right tools and decades of experience before you even get started.
Another great option I haven’t seen mentioned yet is wheelchair wheels. You can order a wheelchair hub with disc brake mounts and lace it to whatever wheel you want and avoid all this mess. https://wheelbuilder.com/phil-wood-rear-wheelchair-hubsets/ has a great option but there are definitely less expensive ones out there.
This is the way. Tried, tested, and reliable. The loads on a bariatric wheelchair axle are worse than most any trike will ever see.
Not invented here syndrome meets heavy metal. These people need to get out more.
Motorcycles have had single-side hubs for ages, complete with disc brakes and chain driven. Apparently I need to replace mine with a bit of bent railway track or something.
Hell, wheelchairs and prams (prams!) have have them.
This feels like a bad idea. Not only is it bad for transferring torque load (since the “spokes” are perpendicular to the hub) but there’s also no longer ANY flex in the wheel. Normal spokes are designed in such a way that they basically only ever see tension, not load. With this design the welds wil get loaded in all sorts of weird direction. On top of that I have doubts the original steel rims would have been a weldable alloy so welding to it might just lead to cracking and breaking of the rims in short order. Lastly I have a sneaking suspicion those wheels are no longer round or centered and there is no way to adjust them.
I would give him the advice to look at here: https://www.atomiczombie.com/tutorials/ and particularly his tutorial on no-lathe trike hubs: https://www.atomiczombie.com/tutorial-no-lathe-trike-hubs/.
Add in the lacing tutorial and everything you need is right there.
(I haven’t actually built any of his plans yet, I’ll get around to it eventually, no need to remind me every six months, but I have bought some of them and they look very complete with detailed instructions.)
This is common on farm equipment in China. It was bonkers to see then, it’s bonkers now.
The issue to be solved here is not that the wheel is only supported on one side. The issue Is the lateral load on the wheel due to the fact that the trike does not lean on corners. Bicycle wheels are designed to withstand mainly loads on it radial direction, not on the axial direction. Wheel chairs also do not lean but, due to its slow nature, don’t suffer from strong lateral forces applied.
Thanks for sharing informative article.