bonded crankshaft

[mgjParticipant @mgj]

I think one also has to remember that in shear even Loctite retainer is less strong than ordinary soft solder. (Or its in that class anyway)

 

It can be very good IF you have a big area. On a Dore Westbury much of the gearbox and the column and head are all secured with retainer – but you are talking of masses of sq inches. Also its less good on the slipperies like bronze, or so I’ve found. 

 

Such cranks, even slender ones that I have done, I followed tubal Cains advice- see Workholding in The Lathe – and added jackscrews and soldered in spacer blocks. Thats done the trick.

 

The other way is to press fit. Racing Kart cranks are press fitted, but that requires very close machining – and accurate pressing, or you end up with a more wriggly crank than otherwise. Kart cranks are pressed up with accurately flat spacers in position and so forth – but even then, have a big moment and the crank can become misaligned and need sorting.

 

I would get the support right and cut from the solid, or create a blank by silver soldering or welding, and then machine with support.

Edited By meyrick griffith-jones on 18/01/2010 21:23:50

[Donald MitchellParticipant @donaldmitchell68891]

Hi Chris,

 

The Loctite I used was 603

 

The parts were prepared to have a close free but shakeless fit. not a tight fit needing pressed, but not loose either. When the Loctite was applied the parts could be easilly put together but no play could be felt. A close running fit.

 

The parts were cleaned with an aerosol can of Valtra degreaser. A fiendish smelling compound used by by a friend to degrease Valtra tractor engine parts when he puts new bearings into them.

 

Maybe I should have used the proper Loctite degreaser but the Valta stuff came at the right price

 

Donald Mitchell
Castle Douglas
Bonnie Scotland

 

 

 

 

[mgjParticipant @mgj]

Donald – that is standard assembly for Loctite and should have been fine- I bet when all fell apart the Loctite was still clinging to the surfaces in places indicating that it had sheared within itself.

 

I have a figure for 601 retainer which is a little older than 603. I fear I exaggerated wildly in my last post. The shear strength is about 2500lbsf per sq inch. Soft solder is between 3.9 and 4 tons f per sq inch. So soft solder is about 4 times stronger than the retainer.

 

Probably why it broke even given good preparation.

[Ian AbbottParticipant @ianabbott31222]

If I remember correctly, the release temperature of Loctite is 300°.  Don’t know if that’s F or C.  Heat to 300 and it falls apart.  This would be important on the inside of an engine, would it not.

 

Ian

[Nigel McBurney 1Participant @nigelmcburney1]

Hi  Best way for small i/c cranks is machine from solid in free cutting en8. I have seen two made for the model gardner in en24 they are superb.  I have made a replacement crank for a full size  1 hp replica engine,I shrunk fit the webs but found that unless there is a fair amount of metal around the bored hole the effect of the fit is reduced as the metal in the web stretches,i also secured with large taper pins ,parallel pin will work loose. Ic engines particularly slow speed singles have lots of torque and the crank has to be sound,A friend repaired a crank for a 1920s 5hp engine,he bored the web of crank,press fitted a new shaft and then welded around the web,its about 4.5inch stroke with 33inch flywheel,after some running the weld parted and the press fit loosened.   Hit and miss engines put more strain on a crank than a more evenly firing throttle governed engines.

[Ramon WilsonParticipant @ramonwilson3]

 

Edited By Ramon Wilson on 20/01/2010 12:03:41

[Ramon WilsonParticipant @ramonwilson3]

Sorry about this but I’ve had problems again, will try to sort it.

Edited By Ramon Wilson on 20/01/2010 12:06:12

[Ramon WilsonParticipant @ramonwilson3]

Hi ,>>

Just like to say how good it is to see all these positive and varying responses and to thank Steve for his kind words and appreciation>>

> >

When Steve first posted his question it’s interesting to realise that none of us actually thought to ask him what type of engine he was intending to build. We all gave him our opinions based on our individual experiences. >>

> >

I must admit however, advocate of the material that I am, it’s now readily apparent that it has it’s limitations and with the experiences of Engine Builder, Donald and Nigel it’s fair to say that its readily apparent that it’s not the right tool for the job in hand for this particular application (larger, hit and miss etc types of IC). >>

> >

Though my steam engine cranks are still ticking over in their low stress environment without a hitch so far  these views have opened my eyes somewhat and though my own thoughts regarding heat induced stresses and distortion remain unchanged I will certainly give more consideration to the options in future.>>

> >

It will be interesting to see how the small shaft in the small Nova engine stands up to the largish prop it has to swing. The area of contact [Loctite] is relatively quite large but it is as yet unpinned – we shall see.>>

> >

Regarding expense of the stuff Rob – that’s something I haven’t had to consider for some time – works sponsored! I’m not sure what you mean regarding ‘capitols’ if it’s ‘Loctite’ then that’s because it’s a product isn’t that how you should do it? Love the bit about Brian Blessed – sorry to disappoint but I’m half his size with a voice many decibels lower!! Do have a beard though!>>

> 

[Ramon WilsonParticipant @ramonwilson3]

This really doesn’t like handling text written in an MS Word doc. Is there a way around this? Can the text be too long as this has cut off in the same place each time. Tried to edit it but that wouldn’t work either.

 

I’ll try to post the remaining bit of text but if that doesn’t work then it’s definitely off to the shed.

 

Frustratingly

 

Ramon

[Ramon WilsonParticipant @ramonwilson3]

>

Couple of other things  – shelf life and degreasing. A long time back (eighties) we had a Loctite rep give a demo at the lace w:st=”on”>Norwichlace> club. Twice in fact with several years apart. lace w:st=”on”>Lotlace>’s of questions obviously but a couple stuck. “Why’s the shelf life so short” Answer was that it wasn’t that important, just there for industry benefit to ensure fresh product used. Case opens and loads of bottles of just out of date up for sale at (very) silly prices. I have some from work that I have no idea how old it is but it still works – now I don’t know what he long term effects will be but it does still work.  On to the degreasing – “What’s so special about ‘Loctite’ aerosol degreaser?” “Nothing it’s just tricho-ethylene” – “Why’s it four quid a can then?” – Roar of laughter all round. “Just use any good solvent” came the embarrassed reply.  Personally I use acetone, does a super job, cellulose thinners will do too but very smelly and to clean any residue I have found the best thing is plain old meths – it kills it ‘dead’.>>

> >

Time to go back to the shed>>

> >

Regards – Ramon >>

> >

PS Writing this in MS Word please don’t get offended if the type goes large!!>>

>

[Ramon WilsonParticipant @ramonwilson3]

When the text is imported to this box from the Word doc it appears exactly as if you were typing in normally – font and size –  it’s only after you have posted that the anomallies appear!

 

What ‘lace’ has to do with NDSME I have no idea. Time for those in the know to jump to the rescue perhaps

 

I’m off to finish the Nova

 

 

[David Clark 13Participant @davidclark13]

Hi There

There is a limit to the ammount of text that can be posted.

regards David

[Ramon WilsonParticipant @ramonwilson3]

Thanks David,

Just for reference and to prevent further embarrassment in the future can you say what that limit is?

 

Regards – Ramon

[David Clark 13Participant @davidclark13]

Hi There

For a forum post it’s 6,000 characters.

regards David

[Ramon WilsonParticipant @ramonwilson3]

Thanks again.

I guess it’s down to using MS Word then as the posting total is less than 3,000 including spaces.

The irritating part is writing it here then seeing it disappear a millisecond before you realise you haven’t saved it

 

Must try harder!!!!!

[chris stephensParticipant @chrisstephens63393]

Hi Ramon,

How are you transferring your word document to the ME site? When i have done it, I highllght the whole thing, then ‘copy’ and then ‘paste’ in the “post a reply” box, which seems to work OK.

chriStephens

PS to highlight , start with the cursor at one end of your document, press and hold down the left button and move the cursor to the other end, then release left button. You can easily see if any is missed. Once it is highlighted you can right click and select “copy”. If you are a Granny and know how to suck eggs, please ignore the above.

[lyricParticipant @lyric]

Hello Ramon,

                         

                              What’s this about “lace” at the NDSME ? 

 The mention of it is getting me exited! and giving me naughty thoughts as I am a member  of the North Devon Society of Model Engineers.

I have no problem with large font  being an old timer.

                                                     

                                                  Best wishes,   Lyric

[Ramon WilsonParticipant @ramonwilson3]

Hi Chris  thanks for your help.

 

No, I’m far from a granny on the computer so all help is most appreciated. However in this instance it appears that I’m doing just what you suggest.

 

After the last enlarged text posting I wasn’t going to do that again if I could help so I made sure the text was small – 9pt and in Arial. When I tranfered it across copying and pasting as you state it appears in the ‘post a reply box’ in Arial at the same size as when you’re typing in there normally (as I’m doing now). (I notice if you save the post box text in reverse to word it defaults as Times New Romant though I always use Arial)

 

It’s only when you hit the ‘post’ button that it appears in larger text with arrows at the ends of paragraphs – too late of course except to delete it as I did earlier.

 

It continually broke the text at the point you see too – if you are not having a problem doing as you suggest I am beginning to think this could be a fault caused at this end.

 

Sorry to turn this post into a computer help topic everyone any help or suggestions will be most appreciated in the meantime I will endeavour to type faster and keep saving the post box text

 

Regards – Ramon

 

 

[mgjParticipant @mgj]

I don’t know about experiences Ramon – I thought that is what one was tapping into. In any crankshaft you have rapidly cycling stresses caused by changes in accelerations, and that’s is not good for any material that is weak in shear.

 

As for making a loctited crank. I might if I were in a hurry and I was building a tiddly oscillator or something.  I would pin, but then it would be the pins that were carrying the shear loads and not the Loctite. (In which case one might just as well press – though the chief advantage of a pressed up (single throw) crank is the ability to fit roller bearing big ends.?).

 

However, I don’t, in general, see the gain. The vast majority of modellers cranks are single throw jobs which, with a simple fixture, are very easy to machine. Bigger, slender, more complex cranks manifestly need more rigidity  in manufacture so jacking systems are essental anyway, and one is committed to the solid or a  brazed blank..

 

I notice by the way that no one thought to ask what the shear strength of the material was – which has a pretty major impact on the decision.

[David Clark 13Participant @davidclark13]

Hi There

In the posting box there is a little button you can click to paste from Word.

Third from the right.

Select from Word, click button.

That should remove any Word formatting.

regards david

 

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