Marzo steering stem

a14rgs

a14rgs

Hero member
Location
Wiltshire, UK
I'm currently reassembling Shaun (Lemonjelly's) RGA Sprint.

Recently collected the frame etc. from the powdercoaters. Shaun wanted the fork yokes blasted, not coated, which they've done. However, in the process, they've removed the stem from the bottom yoke. Whilst I knew this was how they were manufactured, I've never actually seen them apart.

So - the problem I'm now faced with is how to put it back together? I've cleaned up both surfaces with emery tape, then had the stem in the freezer and applied some heat to the yoke.
But they're nowhere near. Even applying some gentle 'persuasion' leaves the stem 15-20mm proud of where it should be.
The stem is now back in the freezer and I've got the yoke warming up indoors.

Is this going to need a mechanical press to get it back together?

Suggestions please!

Alan

p1020977b.jpg
 
As above and if you have no hydraulic press, then get a length of heavy threaded bar inserted through the stem and the yolk with collars on each end, and tighten the nuts against the collars until it's where you want it.

Julian
 
How did they get it out Al, did it just drop out during the 'curing' process ?. Didn't think that they were effectively removable after manufacture.
                                                            Dave.
 
Thanks for the suggestions guys.
I'll bung it in the oven tomorrow morning under the Sunday roast and see what comments I get from the domestic goddess missus :-*
If the heat treatment doesn't work, I'll then ask a favour from my mate who has a hydraulic press.

Ed Case said:
How did they get it out Al, did it just drop out during the 'curing' process ?. Didn't think that they were effectively removable after manufacture.
                                                            Dave.
Click to expand...

Dave, I don't know. Should have asked at the time. If no luck with my efforts, I'll ask if they can press it back in seeing as they took it out. Trouble is, I'm nowhere near their workshop for the next few weeks, and no spare time either during the times they're open :(
 
I?ve pressed lots of them in and out and never had a really tight one. If you warm and chill I would imagine Julians idea should do the trick, just make sure it is well seated so the bearings don?t loosen later. Check that you align the steering lock slot if there is one.
It was discussed a while ago and some people meant it was a no-no however we never had a problem.
 
Will do Tippie, thanks.

Steering lock has been removed from the headstock, so no problems with having to line up the slot on the stem.

I'll go for the "Hot & Cold" approach tomorrow :D

Alan :)
 
While it is out have a look for any cracks in the steering stem. I recall some thread a while back in the MSN site (I think) about cracked stems due to previous crash damage.
Should be easy enough to see since it is detached from the yole.
 
a14rgs said:
I'm currently reassembling Shaun (Lemonjelly's) RGA Sprint.

Recently collected the frame etc. from the powdercoaters. Shaun wanted the fork yokes blasted, not coated, which they've done. However, in the process, they've removed the stem from the bottom yoke. Whilst I knew this was how they were manufactured, I've never actually seen them apart.

So - the problem I'm now faced with is how to put it back together? I've cleaned up both surfaces with emery tape, then had the stem in the freezer and applied some heat to the yoke.
But they're nowhere near. Even applying some gentle 'persuasion' leaves the stem 15-20mm proud of where it should be.
The stem is now back in the freezer and I've got the yoke warming up indoors.

Is this going to need a mechanical press to get it back together?



Alan

p1020977b.jpg
Click to expand...

Alan, I have a friend Henry who is firstly a biker. He runs a well equipped workshop and he will do that for you professionally and without big bucks cost.

Let me know if you need his help..He's a smashing fella to boot !..YOu don't want to bash or stress this ...anytime I need this kind of work or tig welding I go to Henry..He used to work for Jordan racing...so he is good

joe

Suggestions please!
 
Hi Alan - just a thought, you do need to check position of the steering lock slot if you want to be able to use the lock in future.  Also, never has a problem removing or replacing stems, using a press and a bit of warmth.  The interference fit area on your stem looks rather doggy, I have had new ones made in the past with thicker walls for more peace of mind if the original was damaged in any way.
 
Alan,

If you could get hold of some liquid nitrogen from a lab you could chuck the stem into the hole from 20 foot away and not touch the sides.
However, not many people have such a luxury!

In cold numbers (excuse the pun), the spindle/yoke fit is most probably 'Interference'.
For a 1" stem in a 1" hole the stem is 1/2 to 2 thou bigger than the hole. See: http://www.engineersedge.com/class_v.htm

The other option (which you have already selected) is to heat the Yoke. According to my calc's for Aluminium if you heat the yoke from 16 oC to 150 oC then the 1" hole should expand 3 thou. More than enough to slide the stem in by hand.
Of course we do not live in a perfect world, the Yoke is not pure Aluminium and you don't want to get the yoke too hot. But it should work with a margin of error.

The steering lock slot is 90 deg to the 'Y' (long) axis of the frame (with the yoke steering straight ahead) - to the left that is!
 
Done! :D

Stem in the freezer overnight, plus the yoke in the oven for 2 hours at 200'C - then a bit of 'mechanical persuasion' - saw it nicely back together.

Bearings now fitted and the assembly up together in the headstock.

Many thanks for the very useful suggestions guys. Forum to the rescue yet again!  :-*

Alan :)
 
Nice one Alan kept out of this until the happy ending thanks to everyone and especially your wife Alan for you taking over the kitchen!

Shaun
 
SimonR501 said:
If you could get hold of some liquid nitrogen
Click to expand...

Don't forget, a "poor man's" partial substitute for liquid nitrogen is dry ice, often available at supermarkets for very little money. It's nowhere near as cold (only -78.2C vs -210C for nitrogen), but it'll shrink metal parts a lot better than just sticking them in the freezer. It is a solid, so you have to use it to make a cold liquid bath. You wrap it up in a towel, break it into ~1-2 cm chunks with a hammer, then drop the chunks into acetone (water will freeze, metho/meths/denatured alcohol might freeze depending on what's in it) in an insulated cooler.
Check first to see that the cooler doesn't get dissolved by the acetone!
Ken
 
Which supermarkets do you shop in Ken?
Dry ice? Bad enough trying to get ordinary ice.
Dry ice is dangerous stuff, in the wrong or stupid hands.

I used to use it in a lab I worked in once.
Get a piece of rubber tubing, add some dry ice and tie the ends. Discreetly place near someone having a crafty sleep on nightshift, stand back and admire your work when the loud bang (as the dry ice expands on heating) wakes up the sleeper, and half the neighbourhood. Fun times.
 
Grant

Must be a national/cultural thing, water ice is readily available just about anywhere in the southern US (pretty good availability in Oz too, some people there have been known to express a preference for cold beer occasionally :D). Dry ice you have to look for a bit but it's pretty common in supermarkets here.
For me the nearest supplier of liquid N2 is a good 80km away, and I live in an urban area with a population of close to a million, problem is very little manufacturing industry. When I worked in a research job I used to throw the stuff away, very frustrating.

Ken
 
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