E T Westbury Wyvern engine Crankshaft/Flywheels fixing design

I am in the midst of making a Wyvern engine from a Hemingway kit, the cylinder housing and its liner are mounted on the bedplate. Bearings done and ready for the crankshaft. The crankshaft is now made but on both ends the 3/8" dia threaded section is made 3/4" longer than the drawing states. My reason; for possible use of locknuts and puller.

The flywheels are fixed by the use of a tapered split bush nipped in by a single 3/8"nut bearing on each flywheel outer face. This design looks fine until you want a flywheel off again, obviously a puller will be required. A puller can use the extended thread or the end of the shaft to bear on.

However it is just possible that pulling the flywheel off may tighten in the split tapered bush making life that bit more difficult. Has anybody any experience of removing Wyvern flywheels built to the Westbury drawing design? Are they pigs to get off.

I could fit a parallel key and forget the taper.

Thanks.

I use a similar system to fit the flywheels to my engines but drill through the collet and into the crankshaft a bit and fit a silver steel pin. Then when you want to take of the flywheel the collet stays on the crankshaft. The pin is drilled and tapped so a screw may be fitted to remove it. The taper is a good idea fitting a key to a parallel shaft often makes for a wobbly flywheel.

Edited By Engine Builder on 05/08/2012 13:59:58

To Engine Builder,

Spot on, thanks for the prompt reply and a nice simple solution that uses the original design. A 1/8"/5 BA silver steel pin thro the taper sleeve thick end and into the shafts inner end adjacent the shoulder will hold the sleeve virtually at its fixed position when the flywheel is pulled off. A slightly elongated slot for the pin in the sleeve will allow a good tight fit on the taper.

Wonderfull, thanks again.

Terry Knight

Hi. I am just about to start on building this engine from the Hemmingway's Kit. Can you give any advice on if you have run into major difficulties or problems? It's the first IC engine I have built, having done a couple of steam engines from bar stock.

Cheers Andy

Hello to All,

I am a new member and need some help. I have a completed Wyvern engine except for the carb. I have the gun-metal casting for the carb & all the prints but this is beyond what I can do. I was wondering if anyone out there can help me out with the machining of this part. This is really a beautiful engine and would like to get it completed.

Any help would be great!

Neil

There's a description of building this engine here:-

**LINK**

Thanks Max - this is very timely as the Hemmingway plans arrived in the post this weeks with castings to arrive in a week or so. I was planning to start a thread about the build - I will be much slower than you I think. Is it bad manners to join your thread ?

andy

It's not my engine. I've just been following the thread on the other forum with interest.

This thread has got a bit stuck at the moment. I am making the gears and thought I understood how to mill helical gears. Now I'm plagued by doubts.

Rod

Admittedly re-awaking an old thread, but I have the same question as Terence. It looks like ‘Engine Builder’ has supplied the solution, but I don’t understand what is being suggested. I’d be grateful if someone can explain again.

i.e. I don’t understand:

‘I use a similar system to fit the flywheels to my engines but drill through the collet and into the crankshaft a bit and fit a silver steel pin. Then when you want to take of the flywheel the collet stays on the crankshaft. The pin is drilled and tapped so a screw may be fitted to remove it. The taper is a good idea fitting a key to a parallel shaft often makes for a wobbly flywheel.’

David

Slip the tapered collet onto the crankshaft so it butts up against the gear or bearing depending on which side you are doing and then drill through the taper collet say 3mm and also carry the hole through into the crank.

When you come to assemble the collet is slid onto the crank and a short 3mm pin put into the hole to hold it in position on the crank. This pin can be drilled and tapped say M2 so that you can pop a screw into it and use that to pull it out of teh hole if needed.

Myself I have never used the taper loc type fixing for flywheels, I just bore them to a good fit on teh crankshaft and then usually retain with a gib head key, small engines may get a grub screw or two instead. If there is no slop in the fit of teh flywheel to the crank you should not get any wobble.

I see. Thanks Jason – it looks like you went to a bit of trouble drawing that for me. It’s really appreciated.

David

Hi All Question for Rod Jenkins

Hi Rod,

I am currently making a crankshaft for a small marine engine

I've just been looking at your Wyvern build and the way you built the crankshaft.

Can you tell me how you applied the loctite to the shaft and the webs? Not the crank pin that's easy enough

Did you just put loctite in the holes and then push the crankshaft through? Which would of course smear loctite along the shaft as you push it through.

Sorry if this seems a daft question but I may be missing something.

geoff

I am not Rod, but this method may help. I first "loctite" the crank pin into the webs with a piece of shaft material through the other holes for alignment, then leave it to cure. Meanwhile, I clamp a piece of ground bar into a matching pair of Vee blocks that are sitting firmly on a ground surface, with a gap between them, a little larger than the width over the finished webs. I then lift the whole thing and put a little "thread lock" on the underside of the Vee blocks, and temporarily "glue" them to the ground surface they were sitting on. When the thread lock has cured, the round ground bar is removed, and the two shaft parts of the crankshaft are inserted into the web assembly, and the whole thing clamped into the glued down Vee blocks. When all has cured the crankshaft is removed, and a light tap with a small hammer(with a piece of brass interposed) will remove the Vee blocks from the ground surface. Any thread lock on the Vee blocks is easily removed with a sharp blade.The last crankshaft that I assembled like this, I held in a collet at one end and clocked the other end for runout. It was less than half thou.

Hi Geoff,

I did and it does. The Loctite is very fluid though and wipes off easily with a bit of kitchen paper.

Cheers,

Rod

Like Maurice I make up the "U" shape of webs and pin first then when that has cured slip it onto the crank stopping just short of its final position. Apply a couple of rings of Loctite to one side of each web and then slide it into position while twisting the main rod. That way you don't smear it all down the rod.

Having said that I solder all my IC engine cranks and keep the Loctite for small steam engines

Hi, thanks for the replies, useful information.

Maurice in the absence of two matching vee blocks I think I will do what Jason suggested.

Never really occurred to me that you could just glue and slide the crankshaft through , but why not?

Should be good for mine, the crankshaft and pin are only 1/4" diameter and the webs are 5/16" thick, so there is a good bonding area.

I had thought about holding the crank pin in a collet and shouldering both ends to make it easy to set the gap between the webs.

thanks again geoff

A rough sketch of the assembly of a simple crankshaft. If you want it can be silver soldered instead of Loctite. The only motor I have with this form of crankshaft is a small beam hot air engine, the diameter of the shaft and pin is 3 mm, the webs are 2 mm thick, and shaft lock is holding up well.

Ian S C

Edited By Ian S C on 18/09/2017 13:06:30