Hi everyone, great forum.
I’ve searched the forum (and the net) for the answer to this back cand find any real info.
I have a CJ750 outfit impuprted from China. It’s had a lot of simple problems that are pretty much all sorted now except that I’m still bereaking more spokes on the drive wheel than is acceptable.
I break a spoke about every 100 kilometres.
The Sidecar is on the right, we drive on the left.
I’m thinking that because the chair is closer to the centreline, the tendancy is to track toward the bike putting pressure on the drive wheel.
But also the specified toe in is increasing the pressure on the drive wheel.
In all respects the handling is great.
The lead is fixed on these outfits, and can’t be adjusted.
I have about 25mm of lean out.
On a flat road it tracks straight.
The toe in is correct at 15mm - but that’s for riding on the opposite side of the road.
Does anyone know of a good reference on this stuff? Has it been discussed here?
It’s bloody hard just working out what terms to put into a search!
Many thanks
Lindsay
Greetingz Lindsay, Welcome to the slightly off-center world of sidecars!
Spokes on the drive wheel:
- have you checked to make sure the wheel is truly true?
- are there other options to source spokes other than where you have been getting them?
- How often do you check their tension?
- Is spoke quality in question?
- There is an excellent spoke maker in the US called Buchanan's ( https://www.buchananspokes.com/) They should be able to set you up with strong(er) spokes.
Hack on "wrong" side:
By wrong side, I mean when the driver is riding next to the curb. It shouldn't affect spoke life as road camber would have similar effects no matter if the drive wheel is near the crown or the shoulder. The danger is on overtakes. When passing slow vehicles (driven by those damn "Lord of the Rings" tourists, no doubt!), you have to expose A LOT of your vehicle to on-coming traffic before the driver can see if the coast is clear.
Again, welcome! A REAL expert should be along soon to dig deeper into the high failure rate of your spokes.
Are you breaking the wheel down to replace these spokes or bending the spokes to get them in?
Just realised I made a mistake in my first post, the bike is set to lean in, not lean out.
Thanks for the Buchanan’s suggestion, I’ll check them out.
These wheels are Ural M72 type. I’ll include a photo.
I’ve built the wheels myself, and if I ccant get a spoke out easily, I disassemble the rim to swap them.
The original Chinese rims were way out of round. I’ve got 6 steel chromed wheels that came with the bike And all of them had a huge depression where the rim is welded. About 6mm deflection.
So I brought 4 new alloy rims, and stainless spokes from a reputable Chinese dealer (I know..) and asked a local vintage bike genius and long time Sidecar owner to show me how to build the wheels.
I built a jig to lace them while holding everything in the correct place, and a truing stand.
Unfortunately the rims supplied, were for a different style hub, so I had to, by hand and by eye, drill the holes to the correct angle. Then had help to make a cutting tool to cut the seats for the nippels at the correct angle.
Then laced and trued the wheels.
I think the spokes are good quality. I think that a simple test is to put one in a vise and bend it back and forth till it snaps. The spokes I’ve been using seem pretty tough on that test. I can bend them right over 4 or 5 times before they snap.
I’ve also tried a different type of spoke from a didpfferent supplier. I tried a couple of sets of yellow galvanised spokes from Oldtimer garage in Poland. Thinking that galvanised spokes might be slightly springier-less brittle. But they seem to be snapping the same, and seem to be about the same on the ‘bend till it breaks’ test.
Maybe I haven’t checked the tension often enough...
Here’s a pic.
Not an expert here. But years on MZ, Jawa and Ural rigs have taught me that equal tightness of spokes is much more important then center and roundness.
When one gets loose soon 3 will break. Stainless steel does not help much, they are pure cosmetic and much softer then well hardened and unhanealed spokes and nipples. Threads must be rolled never cut!!! observe with the magnifier glass the thead surface and you can tell by the appearance. Tensile strength of rolled thread is with the same ground material factor 2 - 2,5. Thicker spokes are needed for rig use then solo use.
spokes may never be obligated and bow each other, small variations in drill axis and any error when lacing the spokes will cause great unwanted extra load.
Each time i lube my spoke nipples the wrench sound test is done. normally every 2500km. on a slow rig out of roundness does not affect much, 1 loose spoke will weaken and overload the neighbour ones.
2 cent out of a 3 rd world country with very bad roads.
Sven
you have bent spokes ( not straight headed spokes like mine ) that put the load on a bend ( like on bycicles) and on top 2 different lenght with half drum break.+s/c on the wrong side that puts even more load onto the weak long spokes.
outch not much I can suggest on this particular case.
drive cautious like a porcupine makes love.
Very cautious!!!!
Sven
