Author Topic: Maiwald Makeover....... (Read 40348 times)

fcheslop · « **Reply #25 on:** August 06, 2012, 12:07:32 PM »

Hi David,you could also use graphite for the piston
kind regards
Frazer

Stilldrillin · « **Reply #26 on:** August 06, 2012, 05:38:05 PM »

Thanks Nick!
I ummed an arred for a while. Then decided to make a new alloy piston, just to see what might happen.......

Realising there was 4mm spare space below the piston, I made the new one 3mm longer.
It stopped with a clunk, at the wear ridge made by the old piston!

So, I shortened it....... It still insisted on hitting the wear pattern!

So, I built the crank assembly, properly, while I thought about sleeving the cylinder........

The cylinder is 10mm bore, and the bottom of the fins is around 14mm dia.
So, I can only afford a cyl. with a wall thickness of1mm. I have ordered a length of cast iron.

Fraser.
Carbon! That's a great idea....... Until I priced some 3" x 1/2" dia. from Noggin. Hmmm.......

I think I'll try a cast iron piston, too!

David D

fcheslop · « **Reply #27 on:** August 06, 2012, 06:52:56 PM »

Hi David,Try artist supply shops they sell 3 inch lenghts about 3/4 dia for £2 or £3 Iv used it and not had any problems
cheers

ogaryd · « **Reply #28 on:** August 06, 2012, 09:57:06 PM »

Hello David D.
You know we all have one of these but here's my opinion, Graphite for the piston,it's self lubricating&low expansion. I bought my graphite from ebay, it was sold for stiring sticks for molten gold. Straighten cylinder bore and make piston very close fit. Another trick I learned was to remove shields from roller bearing and clean all grease. That reduces friction a bunch. Just another opinion .
I'm enjoying watching your rebuild. Thanks for sharing it with us.
Regards Gary

Stilldrillin · « **Reply #29 on:** August 07, 2012, 03:46:10 AM »

Hi Fraser.
Thanks for the art supplies tip! I'll have a look, while we're out today.

Hi Gary.
Thanks for your rebuild/ sharing comments. They're much appreciated.......

I've seen the stirring sticks...... At around £12, delivered.
Noggin End sell in 3" lengths......... At around £12, delivered.

I only need about 1/2"!

Present thoughts, (it's early morning, yet), are to sleeve with thin wall brass tube, and carbon piston.

This all could change, of course!

David D

Dean W · « **Reply #30 on:** August 07, 2012, 04:56:10 PM »

David, if you have a place in your town that does EDM machining services, check with them about a small piece
of carbon/graphite. They use it for the EDM process.

fcheslop · « **Reply #31 on:** August 07, 2012, 06:13:01 PM »

Hi David,its Graphite you need not Carbon

NickG · « **Reply #32 on:** August 13, 2012, 12:05:36 PM »

Quote from: NickG on July 28, 2012, 10:13:51 AM

... though with this graphite may give you very good results, wouldn't need oil and you could leave the aluminium.

Nick

Ahem .. somebody already mentioned graphite!

I used it in both poppin flame licker engines and they both started immediately ... was so impressed I have plans to replace the piston and valve on my other flame gulper too!

Motor brushes are also a good source if you can find any large enough.

Nick

Stilldrillin · « **Reply #33 on:** August 26, 2012, 06:19:11 AM »

Hi Chaps!
So sorry for the delay.

I've not dropped off the planet, just yet! ...... As a pal used to say. "Everything in me favour's, against me", at the moment.

A bit of gung ho machining of a 5" flywheel, and the lathe gave a couple of gentle pops, and went into quiet mode!

Since then, several aspects of daily life have gone wrong. And, a lot of other things haven't gone right.

It's blummin amazing, how everything comes at once!

The Maiwald parts lie just where I left 'em. Before they were covered with multiple parts from the stripped lathe..... Which is now rebuilt, again!

Give me a few more days..... Probably!

David D

Stilldrillin · « **Reply #34 on:** October 05, 2012, 02:13:17 PM »

Well..... It's been quite a while since I did any orphan work. But! the big news is....... I've got Maiwald work underway, again!

Assembled together what I could find........

Cast iron. Graphite. Brass tube. Also, 2 packs of M2 grubscrews...... Dunno what they are for!

And set up, to drill for cylinder sleeve......

Then...... The phone rang!

No time to get back to it, until next week. But....... We're progressing, at last!

David D

Stilldrillin · « **Reply #35 on:** October 08, 2012, 03:38:18 PM »

I drilled out the cylinder with 7/16" drill, held in a 12mm R8 collet. Didn't think R8 collets would compress willingly, that far.....

The 7/16" K&S tube needed it's o/d reducing by a couple of thou. So, I turned a mandrel......

Leaving the o/d a little rough, for grip, stuck it in place using my favourite sleeve retainer.......

Will drill through to the displacer chamber tomorrow, when it's cured.

Question time now. Re-graphite pistons.......

I've never turned a piston, without some oil grooves.

Do I still groove a graphite one. Or, leave it plain?

David D

lordedmond · « **Reply #36 on:** October 09, 2012, 06:58:33 AM »

David

leave it plain. and bring to final size with brown paper for emery, cover every thing up inc. yourself it gets everywhere

barriers cream on the hands is a good idea

with CI I am banished to washing hands in a bucket same with graphite

Stuart

NickG · « **Reply #37 on:** October 09, 2012, 02:17:25 PM »

Yep I'd agree leave it plain. I woul personally just turn it to size taking very small cuts will keep it parallel you'll find a very slightly tight fit, not tight but not fall through on it's own loose, will quickly wear it's way into the perfect fit after a few rotations of the crank. No need to lap or any such daft things it will create it's own perfectly smooth finish providing it's not as rough as a badger's arse. No need to cover stuff up, it's a good lubricant for machine, messy though!

Stilldrillin · « **Reply #38 on:** October 11, 2012, 12:13:17 PM »

Well....... I managed a workshop hour, this afternoon.

Pity it wasn't more productive.........

I was trying to emulate the original piston, only longer........

Guess I'll have to make a clevis, down inside the skirt. Held in with an M3 screw from 'tother end.

This stirring stick graphite is a lot coarser than I imagined it would be!

David D

NickG · « **Reply #39 on:** October 11, 2012, 03:50:51 PM »

Hi David, shame about that - it does look coarser than the stuff I used but reckon it'll still work - it looks sort of metallic? I've never tried threading it, do you need to? Also, do you need to mill the slot for the rod right through it? I left some material around edge on mine for strength and made the gudgeon pin a push fit in the graphite and a sliding fit in the rod - then you can assemble with light pressure and if the pin is slightly shorter than the dia. of the piston it will never move, the pin is stationary.

see attached for how I do mine, just a thought.

Nick

Stilldrillin · « **Reply #40 on:** October 16, 2012, 12:43:13 PM »

Thanks Nick.

So, I made one........

It reminded me of compressed, dried leafmold.......

Couldn't polish it to round. It went all shapes, like a piece of grainy softwood.

And, the engine would only run, when persuaded with a small blowlamp.

Think I'll make a brass piston, if I can get the time, tomorrow.

David D

NickG · « **Reply #41 on:** October 16, 2012, 12:56:53 PM »

Nightmare!

Well at least you've tried it, looks like I got lucky with the piece that was donated, it was much finer, more like the stuff you seen on motor brushes.

Looks like brass might be the way forward for you then, I just struggle with the whole lapping / getting a perfect fit thing though!

Nick

andyf · « **Reply #42 on:** October 16, 2012, 02:13:28 PM »

m-machine are advertising a new plastic with a great fanfare. They say it works OK for piston rings; I wonder if it would be stable enough for a complete piston.

It's on this page:
http://www.m-machine-metals.co.uk/mm/website/metals_menu.html

Andy

philf · « **Reply #43 on:** October 16, 2012, 03:05:36 PM »

Quote from: andyf on October 16, 2012, 02:13:28 PM

m-machine are advertising a new plastic with a great fanfare. They say it works OK for piston rings; I wonder if it would be stable enough for a complete piston.

It's on this page:
http://www.m-machine-metals.co.uk/mm/website/metals_menu.html

Andy

Looks an interesting and useful material. At £8.37/ inch of 25mm diameter it's not cheap. To quote from a data sheet:

Main characteristics:

high max. allowable service temperature in air (continuously 260°C)
excellent chemical and hydrolysis resistance
good wear resistance
low coefficient of friction
very good dimensional stability
good electrical insulating properties
oustanding UV and weather resistance
inherent low flammability

FLUOROSINT® 500 (PTFE + mica) (ivory)

FLUOROSINT® 500 has nine times greater resistance to deformation under load than unfilled PTFE (tested according to ASTM D 621; stress of 14 MPa of 50°C). Its coefficient of linear thermal expansion approaches the expansion rate of aluminium and is 1/5 that of virgin PTFE. It is considerably harder than virgin PTFE, has better wear characteristics and maintains low frictional properties. FLUOROSINT® 500 is also nonabrasive to most mating materials. .

Phil.

Stilldrillin · « **Reply #44 on:** October 17, 2012, 12:38:22 PM »

Nick.
I probably should have spent more, on a better quality piece of graphite......

Andy.
I think that will do the job! But, at the price Phil's come up with, it might be some while before someone tests it.......

Well...... I made a brass piston. It looks much better than the compost one!

It even runs much better.........

All parts are just bodged together....... It wasn't really happy, but I left it running for some 10mins or so.

Stopped it. And realised, the clonk was the piston hitting the bottom of the cylinder!
1mm removed, tomorrow, should make all the difference.

Ready for finish build, now......

Happy little Drillin!

David D

lordedmond · « **Reply #45 on:** October 17, 2012, 01:16:57 PM »

Quote from: andyf on October 16, 2012, 02:13:28 PM

m-machine are advertising a new plastic with a great fanfare. They say it works OK for piston rings; I wonder if it would be stable enough for a complete piston.

It's on this page:
http://www.m-machine-metals.co.uk/mm/website/metals_menu.html

Andy

I think its similar to PEEK , I use that stuff for the polo mint type rings on piston valve bodies

Stuart

NickG · « **Reply #46 on:** October 17, 2012, 01:24:23 PM »

Nice work David ... looks like it's flying over in the pic!

I noticed that material too but never thought of using it for a piston. Might get hold of some and see what it's like considering they are only about 6 miles away from me!

Stilldrillin · « **Reply #47 on:** October 18, 2012, 07:53:04 AM »

Thanks for your comments Chaps!

Someone wanted a video, already........

David D

saw · « **Reply #48 on:** October 18, 2012, 10:11:56 AM »

Nice work the engine is running nice and fine

Stilldrillin · « **Reply #49 on:** October 24, 2012, 03:43:47 PM »

Thank you Benni!

When I first saw this engine, with it's large flywheel, it reminded me of a hit n miss engine. Which needs a pair of wheels......

I've now chopped rather a lot of ali from the castings.

With red spokes, would this look ok?

Or, are they a little on the large side?

David D

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Author Topic: Maiwald Makeover....... (Read 40348 times)

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