Kids scooter - loose handlebars

[Ian Geary]

(Think this this the right forum)

I have a problem with a scooter

In brief
- brand new scooter bought for kids birthday
- UK made to replace Chinese junk one: not hugely pricey but has good reviews

- fitting handlebars to headstock is done by tightening a collar with the Allen key provided (ie no excessive force should be required)

Problem: the clamping force is not sufficient to keep the handlebars aligned to the front wheel

A bit more detail
- the head stock is itself a metal collar and cap sitting over the headstock, which has a small Allen bolt down into the headstock "proper" and bearing assembly
- this Allen bolt is not particularly tight: not thread locked or a locknut etc.


So the hand tight clamping force has to act through the handle bar metal, through the head bearing cap and onto the inner surface of the head stock to keep the front wheel straight


The metal is all smooth, no splines or crosshatching or shims, no locking key etc, but there are cut outs to allow compression.


Here's the handle bar
Pics


The cap and collar around the headstock


The clamp (aluminium) to keep it all together



I've contacted the shop as I don't think it's safe to use, but has anyone else come across this, or have any ideas?

- thought one was to just tighten the collar flippin' tight with a socket. But I think the steel screw will strip the ali thread, voiding any warranty. And with about 1-2mm of available closure (hand tight), I don't think it can clamp onto tjr headstock through 2 layers of tubing sufficiently (the clamp is open by about 8mm but it's very stiff)

- thought two was to insert some sort of shim or packer between the 3 surfaces that have to be held together - runner tape? Pvc tape to improve the grip?

- thought 3 is to return it as unfit for purpose, but this seems to fly in the face of reviews.



Thanks

Ian

[littleredrooster]

Where is the slippage occurring? Is it between the handlebar and the collar, or the collar and the stem?

If the latter, should that central cap-head bolt not be tight enough to hold the collar to the stem?

[dudleybloke]

Is there a slit in the longer bar to allow it to compress?

[pocketspring]

Go to an engineering shop and ask them to make a shim collar to put inside.

[LennyM1984]

pocketspring said:

Go to an engineering shop and ask them to make a shim collar to put inside.

...Or save yourself some money and: drink a beer from a nice aluminium can, cut can into a long strip, wrap your newly acquired aluminium shim around handlebars, clamp! I did this many times as a kid when fixing my bike (with a soft drink can rather than beer).

[zedx19]

https://www.youtube.com/watch?v=ECPaS_I6wh4

This video shows something similar (maybe same?) being placed on, then tightened up.

[Ian Geary]

Thanks for all the replies so far

zedx19 said:

https://www.youtube.com/watch?v=ECPaS_I6wh4

This video shows something similar (maybe same?) being placed on, then tightened up.

Yes, that is the exact scooter. Luckily I didn't need his "pro tip" of how to fit handlebars (which, for those who didn't see, is basically to fit the handlebars)

He said to tighten it until you can't anymore, but unfortunately it didn't zoom in on how tight he got the collar to close. I could try a bit more umpf. I was doing it evenly across the 2 bolts of course.

littleredrooster said:

Where is the slippage occurring? Is it between the handlebar and the collar, or the collar and the stem?

If the latter, should that central cap-head bolt not be tight enough to hold the collar to the stem?

It's hard to tell exactly, but I suspect the inner collar is rotating on the headstock itself. Because whilst the compression force is ok to clamp the handlebars to the collar, it's not enough to also squeeze the collar onto the actual headstock.

What I might do is refit the handle bar say 50% down rather than flush down, so I can observe what is moving against what.

I can't believe the poxy central Allen bolt is supposed to take the force of the steering. I recall from biking days a mountain bike head stock would have a wedge that gets pulled up by the central bolt to expand inside the front forks.

This has none of that - just a small 1 inch hex bolt.

I might also try a shim - nothing to lose really.

Ian

[gazza285]

The central cap head is to set bearing preload, it is not there to prevent the collar spinning on the steerer tube.

I presume the collar is also split, and you are aligning the split in the collar with the split in the handlebar tube?

[wildoliver]

I don't like the idea of tightening the clamp till you can't any more. Sounds like the socket is too big for the insert and if you can tighten the clamp enough without stripping the bolt thread at best you will crush the tube. Shimming is the answer.

But it doesn't sound a high quality UK made product to me. More a Chinese product that's been put together enough in the UK to claim UK made and then price hiked. I'd send it back.