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Steering stem/fork-yoke fitting

Submitted by julian_wells on Wednesday, 28 February, 2018 - 00:00
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Commando

Just going through some (very) old issues of "Motor Cycle" that have come to light in a sort-out (I know ... )

In the issue for week ending 15/12/73 there's a picture caption story in the "George Stratton" Talkabout* feature showing stems being glued into the yokes using Loctite 601-RC35; claimed advantage over press-fitting is reducing the risk of sloppy fit on the one hand, or on the other, fracturing the cast-iron yoke if the stem is over-size.

The load to press out a glued stem is said to be six tons !

* Usually by the late John Ebbrell.

Submitted by david_cooper on Thursday, 1 March, 2018 - 00:02

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No idea about this, but in answer to the magazine's question "where does the home mechanic get such a press" is presumably that the 6 tons is a cold force - the home mechanic could warm it all up to maybe 150C and it would slide out.

Almost as interesting is to ponder how times change. No magazine nowadays would print such a question: chuck it away and buy a new one!

Submitted by ian_soady on Friday, 2 March, 2018 - 00:00

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Many thanks Julian.

As an aside, I've always thought the later Commando steering head bearing layout is so much better than most other bikes. No balls to lose, and impossible to overadjust. When I first rode the Guzzi V50 I bought in the summer, I thought there was something dreadfully wrong with it till I discovered that the steering head bearings had been tightened down with what must have been a 3 ft long spanner.

Adjusting them correctly saw the excellent handling restored. Fortunately the races hadn't brinelled.

Submitted by julian_wells on Friday, 2 March, 2018 - 00:03

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As you say, times change (tho' not of course in the various classic bike mag.s).

On pressing out the stem; you're obviously right in the case of an interference fit -- but I think the point being made in the article refers to the glued-in variety; indeed, reference to the following suggests that heating to 150?C would have no effect.

http://www.henkel-adhesives.co.uk/2838_UKE_HTML.htm?nodeid=8797709631489

LOCTITE 601

High strength, dimethacrylate ester-based retaining compound with medium cure speed and low viscosity; suitable for filling small gaps.

LOCTITE 601 is a green, anaerobic, low viscosity, medium cure speed, dimethacrylate ester-based retaining compound suitable for a max. diametrical clearance of 0.1 mm. It is a high strength product for applications that require a permanent bond. Fixture time on steel is 25 min and service temperature from -55?C to +150?C. Fluorescence allows product presence to be monitored.

Your Benefits

  • 1-part product, requires no mixing
  • Medium cure speed
  • High strength for permanent bonds
  • Low viscosity, small gap filling
  • Fluoresces for presence monitoring

Previously David Cooper wrote:

No idea about this, but in answer to the magazine's question "where does the home mechanic get such a press" is presumably that the 6 tons is a cold force - the home mechanic could warm it all up to maybe 150C and it would slide out.

Almost as interesting is to ponder how times change. No magazine nowadays would print such a question: chuck it away and buy a new one!

 



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