Mery Explosive Engine

[Chipmaster]

Cheers Stuart, L'm looking forward to seeing your beam engine take shape. Perhaps my start to finish build log of my Stuart Major here on MEM might come in handy as they only appear to differ in size.

I didn't have enough time to finish the crankshaft today, it still needs to have keyways cut in each shaft and the crankpin polished. I used correction fluid to resisit  the silver solder but it still managed to adhere in a few places, particularly the crankpin.

Crankpin in place

IMG_3356 by Andy, on Flickr

Prepared for silver solder with correction fluid and flux.

IMG_3360 by Andy, on Flickr

Silver soldering.

   IMG_3363 by Andy, on Flickr

Cooled down and mucky.

IMG_3364 by Andy, on Flickr

Crankshaft Number 2 well on the way.

IMG_3366 by Andy, on Flickr

IMG_3367 by Andy, on Flickr

Andy

[propforward]

Cheers! I just bookmarked your beam engine build - will for sure refer to that. Aaaaaaaaand I already nookmarked this one for when I start on my own Mery engine. I picked up the castings a while ago.

Great job on that crank as well. 

[Chipmaster]

Milled the 1/8" keyways in the shafts

IMG_3368 by Andy, on Flickr

Flickr video of my old Archdale milling machine in action, still going strong.

IMG_3371 by Andy, on Flickr

IMG_3374 by Andy, on Flickr

When I ran the engine in by driving its pulley belted up to an electric motor the flywheel was a good fit on the shaft and ran perfectly true;

<a href="https://www.youtube.com/watch?v=Y2m2B9I4Nh0" target="_blank">http://www.youtube.com/watch?v=Y2m2B9I4Nh0</a>

However, after many runs the flywheel become loose on the crankshaft as its bore is now slightly worn. I ran the engine briefly today with its new crankshaft to check that the main and big end bearings are ok. 

My next task is to bore out the flywheel's hub, fit a sleeve retained by loctite and rebore the hub to achieve a close fit on the shaft. I might make the sleeve / hub deeper to increase contact area with the shaft.

Andy

[Chipmaster]

The flywheel hub being bored out to 3/4" (Flickr video)

IMG_3380 by Andy, on Flickr

IMG_3409 by Andy, on Flickr

On target 0.75000", that's unusual for me.

IMG_3411 by Andy, on Flickr

Cast iron bar machined to form a slip fit plug. I thought a press fit would risk cracking the casting.

IMG_3417 by Andy, on Flickr

Glued in with Loctite 638

IMG_3421 by Andy, on Flickr

IMG_3422 by Andy, on Flickr

Ceanothus growing on the back of my garage. It's buzzing with bees already and usually the flowers become even more dense.

IMG_3424 by Andy, on Flickr

I will allow seven days for the Loctite to form its strongest bond then I'll return the faceplate complete with flywheel still attached to the lathe and bore it out to a snug fit on the crankshaft. I hope the flywheel will still be concentric with the faceplate and run true when it's back on the lathe.
Will have to find another project for a few days. 

[Roger B]

The Mery is looking good     

How is the flywheel fixed to the crankshaft, is there a taper key?

[Chipmaster]

Hi Roger, yes the flywheel is held by a taper or gib key.

Mery Gib key by Andy, on Flickr

Unfortunately I'm not proficient with fitting gib keys. I suspect my ill fitted gib key led to the flywheel working loose and wearing the hub. The Mery uses a 1/8" gib key and I have bought some ready made from Tasman Industries https://www.keysandpins.com/products/gib-head-keys. Whether I make my own or use ready made keys it takes me ages to acheive a fit, I broach the internal keyways in the flywheel hubs. Sometimes I think a few more file strokes will do the trick only to find the key is then loose. 
I have considered smearing Loctite 660 on the key as it is often shown as a remedy for damaged keyways and splines but what if you need to remove the key and flywheel in future ?
Any opinions or experience gratefully received.

Andy

[Alyn Foundry]

You should have given me a ring Andy.
I still have a stack left over.
I’m now using ‘ C ‘ broaches at 1/8” as they’re a lot less brittle than the ‘ A ‘ types.

My method is to broach the first cut then with the slip for the second cut but only to the last tooth before pushing out the broach backwards. This ensures yo have the correct taper. 😉

   Graham.

[Jasonb]

I make tapered bushes and drive the key right through.

[Dave Otto]

I make tapered bushes and drive the key right through.

That is my method also.
It seems that if you push the broach back out that it would leave a terrible finish in the key way because of the partially cutting teeth.
I have also made thinner shims and used them to sneak up on the fit, sometimes the standard shim that comes with the broach is just too thick.

Dave

[Chipmaster]

Thanks for your responses.

I have a Marlco Number 1 set of imperial broaches that includes a motley collection of shims that don't correspond with the data on the card.

IMG_3442 by Andy, on Flickr

IMG_3445 by Andy, on Flickr

I took the plastic card insert out of the lid to clean and scan it......

Marlco Broaches 1 by Andy, on Flickr

Consequently saw the reverse side i of the card which goes into detail about tapered keys. I was not aware of this information until this afternoon.....

Marlco Broaches 2 by Andy, on Flickr

The broaches all measure 0 31" wide which I presume would be classed as 5/16" and the teeth increase in height as expected. However, I don't appear to have the 'T' type guides referred to in the Note at the foot of the card. So I'll have to try and work out what taper keyway I've been broaching and would it make a significant difference if I rely on the taper cut by a broach that hasn't been pushed right the way through?

Andy

[steam guy willy]

good work on the flywheel ..7 Days to cure it ??  I have always  wondered  if the manufacturers attached a cross slide to the finished engine to true the flywheel up with the engine running ???  I have sometimes thought this would work on a model ??!!!

willy

[Chipmaster]

Hi Willy, yes 168 hours to reach full strength according to the Loctite data sheet.

https://datasheets.tdx.henkel.com/LOCTITE-638-en_GL.pdf

I’m not in a hurry so don’t want to risk upsetting the Loctite bond.

I admire your work on what is a far more complex and demanding model.

Regards
Andy

[Chipmaster]

Hi Jason and Dave, I think I’d be hard pressed to machine a guide with an accurate built in tapered / sloping slot or perhaps I have misunderstood you. Do you have any pictures of your method that you could post please?
Andy

[Dave Otto]

Hi Andy

I can't put my finger on it right at the moment, I made an aluminum piece like a parallel with the proper 1/8" per foot taper on it. then it was just a matter of putting the bushing blank on the aluminum part in the vice and cutting the slot for the broach body. What I don't remember is how I figured out how deep to cut the slot. It just needs to be deep enough so the broach can enter the bore, then you can shim from there, after the first pass. I would do a test part before I committed to the flywheel.

Dave
 

[Chipmaster]

Ok Dave thanks for your reply.
Andy