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Wyvern crankshaft question

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NR6714/05/2022 14:47:11
15 forum posts
5 photos

All the parts are now machined for the crankshaft of my Wyvern engine. My question is about the best way of joining them together. As far as I can tell the pins are a tight push fit into the plates but I dont want to push them fully home until its all aligned. Silver solder, Loctice 603, Straight knurl and press in, pinning are various methods Ive read about. Ime minded to loctite and maybe pin because once completed I guess the engine will be run for 10 minutes a year, no more. soldering may need further machining if it spreads too far and ide rather not. If I loctiite is it best practice to machine a shallow groove in the pin so there is space for it, especially if they are tight fitting? Any ideas greatly appreciated.

Thor 🇳🇴14/05/2022 15:39:19
1628 forum posts
46 photos

I have made built up crankshafts using anaerobic glue and pins. My pins could be pushed in by hand so I didn't groove the pins, the crankshaft is still working 2 years later. I have also made built up crankshafts that I have silver soldered (brazed) together, I machined the crankshaft after soldering and pickling.


JasonB14/05/2022 15:52:17
22749 forum posts
2653 photos
1 articles

I usually silver solder built up cranks for IC engines and keep the Loctite for steam and hot air where things are a bit more gentle.

PatJ14/05/2022 16:41:35
367 forum posts
410 photos

As I understand it, all of the single cylinder motorcycle engines have pressed together cranks, with no pins.

So if it works for a motorcycle engine, why not use it for models?

Perhaps too tedius to try and press in the pieces without damaging something?

Is there a special method used to press together motorcycle cranks?

Just curious.


bernard towers14/05/2022 17:52:46
618 forum posts
109 photos

Modern single motorcycle cranks are a press fit but also the shafts are taken from liquid nitrogen in a controlled atmosphere, we can't do that plus our engines do not put out massive amounts of hp per cc

duncan webster14/05/2022 18:13:16
3984 forum posts
65 photos

The crankpin holes on old British bikes were tapered so you Coul push them nearly home but still adjust by putting between centres and hitting with a lead hammer. Having broken a hydraulic jack trying to dissemble a loctite joint I have great respect for it

NR6716/05/2022 06:47:47
15 forum posts
5 photos

I decided in the end to use loctite and in stage 2 to cross drill and pin, again with loctite. Assembly in 2 stages. First the big end journal with a temporary main bearing journal that was continuous to keep alignment. A temporary spacer between the webs keeping them parallel. Second phase is to fit the permanent main bearing journals. A jig to ensure these are in perfect alignment and clamped is for today. Probably a piece of ground bar and parallels used in a temp arrangement. Thank to all for the various ideas and information on crankshaft construction.

Samsaranda16/05/2022 09:44:30
1430 forum posts
5 photos

I remember my Matchless G80 crankpin had thin nuts locking the outer ends of the crankpin. Dave W

Nigel McBurney 116/05/2022 10:27:42
1000 forum posts
3 photos

A mild shrink fit,then secure with taper pins driven home hard, too severe a shrink fit does not improve the fit as the metal surrounding the shaft or crankpin just stretches. a full circular crank disk having a central shaft can have a tighter shrink fit as there is a lot of metal surrounding the shaft and the disc will not stretch. A friend made a couple of crankshafts for the Model Gardner engines out of solid using en 24 no problem with those,though he is a good machinist. Graham Corry of Alyn foundry silver soldered his cranks for the Gardner and other models,I made 4 of the Robinson hot air engines and with such a low power Loctite made a good job of it and requires no cleaning,Graham used a high temperature silver solder flux to get a clean joint .

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