Another Paddleducks build log

[spuddevans]

Well, I havent forgot about this project, real life just got in the way for a bit, but I hope to get back to this build when I get home and have assembled my latest toy piece of vital workshop equipment. ( A bandsaw, woo hoo  )

Before I set off for the mainland UK I did manage to reduce down both Eccentric Straps to fit their relative eccentrics. I did end up flycutting one as I had to reduce it from 4.00mm to 3.84mm and this piece of 4mm brass sheet seems to be incredibly hard stuff. So I just took a very slim cut off with the little flycutter, and then just cleaned up with some wet-n-dry ..... and it fits 

So next will be drilling the oil cups, then I have to scrounge up some firebrick-type-materials to make a hearth to Silver Solder the straps to the strap-rods ( please notice the use of the technical terms there  )

I also need to shape the straps a bit to lessen the square-ness of them.


Tim

[NickG]

Tim,

Am sure you know what you are doing but just be careful with 'fire-brick type materials' if you don't know what they are! Am only saying this because years ago I was soldering something on a brick my dad thought was a fire brick and it started exploding! Chunks or the brick started fragmenting and flying off at high speed .. luckily didn't hit me but could have had my eye out!

Nick

[spuddevans]

Hi Nick, I appreciate that, I intend to go into a fireplace place to ask if they have any broken bits they could throw me.


Tim

[NickG]

Great idea.

[dsquire]

Nick and Tim

I am wondering if the fact the bricks exploded had anything to do with the fact that they held moisture? I know that I have read on metal casting sites not to pour molten metal over concrete as this can cause explosions. Also, wet sand is a no no when metal casting.

Cheers 

Don

[NickG]

Don,

Could be I guess, pockets of moisture flashing off inside. I don't know, I just put that brick to one side and didn't use it for that any more!

Nick

[spuddevans]

I found a couple of photos of the eccentric straps so I thought I'd share them.

These are the straps before I started on the whole thinning and then boring the holes for the eccentrics.



And this is them after much sweat, tears and tantrums, well, sweat and tantrums anyway.


You can see the extra holes that I broke the drills in as mentioned before. I will be cutting those portions away when I shape the straps.

Stay tuned for more updates, shouldnt be too long for more progress as I've got my bandsaw up and running now.


Tim

[spuddevans]

So I got a bit more progress made, Stefan (Spynapples) came over last night and we got some work done on the eccentric straps. We started by drilling the 3mm holes for the connecting rods, and with that under our belts we carried on to drill the little oil-cup-hole-thingys. It was at this point things started to go a little pear-shaped.

1st off we discovered that my 1.5mm drill bit is as sharp as a kleenex (mansize of course), so after burning a 1mm deep hole we switched to a 1.4mm bit. This went through the brass like, well a sharp drillbit through brass. We drilled thru with that then we followed up with a 2.5mm bit to a depth of about 5mm to make a little resovoir-cup-thingy.

Now riding on a crest of a wave, congratulating ourselves on making such a fine job of the 1st strap, we ploughed on to the other one. The 3mm hole for the connecting rod was installed without a hiccup, and the 1st 6mm of the 1.4mm oil hole went swimmingly, and then  The drill snapped. Cursing this unknown grade of brass sheet for being so tough we were forced to stop. ( We had been drilling using top speed (about 4800 rpm ) and also were "pecking" taking about 0.5-1mm per "peck" )

After a little thought we decided to try drilling thru from the other side, sounds simple except this meant drilling from the inside curved surface where the eccentric would sit. After carefully marking out where the hole should come out we started with a tiny centre drill at full rpm's and very gingerly started the hole. After about 1mm depth we switched to a 1.3mm bit ( crumbs, if I break any more on this the oil hole will be <1mm!! ) and again very carefully drilled thru to the broken bit ( if you are very gentle you can hear when the drill gets to the broken bit ) then withdrew. Then, using a thin awl we gently tapped the broken bit thru until it fell out.

It's funny how things can go wrong on the final operations on a piece, but we figured we had little to lose by making this attempt at a save, and it turned out ok. Here's a pic looking down on the 2 halves of the straps as we left them last night.



Then this afternoon I got a bit more done on the shaping of the straps. I milled away a little on each strap and ended up with something that looks a little art-deco ( completely by accident mind you ).



Then I turned down some 4mm brass rod to 3mm and cut off 2 18mm lengths for the connecting rod for the straps.


That's all I got done today. Next will be the forks, blocks and pins for connecting the eccentric to the piston valves.


Tim

[bogstandard]

Tim,

Really I think you are taking things a little too literally.

The oil hole is just that, a place to wack a bit of oil into. It could have been a lot larger, within reason. It was just a way of reminding people that it is a hole and it is there for a reason. When lubing up the engine, you see a hole, what is it for?, you remember that a spot of oil is needed down there occasionally, job done.

It is only when you use a calibrated drip feed hole from a small reservoir that you need to worry about things like that.

But coming along just fine now, you will soon be ready for the first air trials.


Bogs

[spuddevans]

Tim,

Really I think you are taking things a little too literally.

The oil hole is just that, a place to wack a bit of oil into. It could have been a lot larger, within reason. It was just a way of reminding people that it is a hole and it is there for a reason. When lubing up the engine, you see a hole, what is it for?, you remember that a spot of oil is needed down there occasionally, job done.

It is only when you use a calibrated drip feed hole from a small reservoir that you need to worry about things like that.

But coming along just fine now, you will soon be ready for the first air trials.


Bogs

Ahhh!! I didnt know that it could've been made bigger. That'll be my inexperience with engineering-type-stuff showing thru again, oh well, everybody has to learn, I've learned from this, and hopefully others can read this and learn from this too.

I do have to say, even though an awful lot of this is very new to me, and there have been some frustrating moments that make you want to chew your own foot off, all in all I am absolutely loving this!! And being able to share it all with the rest of the forum and benefit from the collective wisdom and advice is great too.

Tim

[bogstandard]

By making this engine Tim, it will shorten your learning curve by copious amounts, because you are using techniques not normally encountered by someone fairly new to machining. You are finding that the techniques have no fear in them, when you actually get shown how to do it. There is no black magic about it, just logical thinking.

After this, you will be able to tackle a lot more complex items without having any fears about the operations needed.


Bogs

[CrewCab]

oh well, everybody has to learn

Tim, don't fret, that's why we are all here 

there have been some frustrating moments that make you want to chew your own foot off, all in all I am absolutely loving this!! And being able to share it all with the rest of the forum and benefit from the collective wisdom and advice is great too.

Same answer as above 

If it wasn't fun .............. why bother 

CC

[Stefan Pynappels]

I have to say Tim is a lot calmer in the face of (drill bit) adversity than I would be, he just gets on and thinks of a fix.  And don't be fooled by the modesty, he has a much more technical and analytical head on his shoulders than he gives himself credit for. I reckon he is a natural engineer...

[spuddevans]

I have to say Tim is a lot calmer in the face of (drill bit) adversity than I would be, he just gets on and thinks of a fix.

Dont believe a word of it!! Underneath all this dirt, grease, oil and swarf there is something else...... More dirt!!! But underneath that there beats a heart of a little wannabe model engineer.


Anyway, now that my head has swelled enough for this year, having some time off the mundane drudgery work I got a little more progress made this morning, starting with the blocks.

I started out by cutting off a chunk off the same 4mm thick sheet (well, hardly a sheet, more like half a hankichief) of brass that I made the eccentric straps from. and then mounted it the mill-vice to make the cut edge flat and parallel.


Then after a little cutting to size and milling I ended up with these


Then after a little drilling they were done, here they are in place ready for silver soldering. ( I plan on doing a few practice joints before attempting to SS any of the parts for the engine, just to be on the safe side.)



Just on the subject of Silver Soldering, and especially to those who have built the Paddleducks engine, how did you stop the silver solder from blocking up the oil hole on the eccentric straps? The oil hole is only about 1mm from the soldered joint for the con rod. Any hints or tips?


Anyway, getting back to the build.

After this I had a bit more time, so I made a start on the Forks ( "use the forks, Luke" (said in best Obi-Wan impression)    )

Not having any 6mm square brass stock I sliced off a 8mm chunk of the 19mm square bar I have, flycut it on both sides to 6mm thick, then cut it down and milled it to 11mm on one side, then cut the other side ( the remaining 19mm side ) down and milled it to give me 2, 6mm x 6mm x 11mm blocks for the forks.


So next time I will be drilling, tapping and milling the forks into shape, then it'll be on to the valve packing glands ( which I already have made the nuts for thanks to Kvom  for telling me that they were the same as the piston packing gland nuts, so I made extra when I made them.)

Tim

[Darren]

Tim just caught up on your progress, had a quick flick through all the posts .... !!!

Coming on well ..  

Regarding all the snapped drill bits .... I too have been exactly there with the same parts  

Did you use plate brass by any chance? Alli bronze .... I could not drill that stuff for the want of trying , snap, snap, snap, and so on about 10 drill bits in all.

Then I used a bit of free machining brass ................ no problemo ....

[NickG]

Tim,

Great write up ... may the forks be with you 

I don't buy any of this modesty stuff for a minute ... you've already proved you're a great model engineer and photographer. It seems you're one of those annoying people that can do anything from where we're looking ... a master of all trades!!!!

  Her indoors has enrolled on a free photography course that she saw in the local rag after buying the new camera. She's only been to 1 session so far but will have to see if it improves her skills! If she's any good, I may promote her to chief photographer whilst still covering her tea lady duties!!! - Who am I trying to kid, haven't had a cuppa brought to me in the workshop once yet! 

Nick

[bogstandard]

Tim,

With regards to the silver solder, it all depends on whether you are using the fine wire or the normal rod.

With the fine wire, you just coil a little around a drill of the same size as the hole you are soldering into, and split it along the edge to form little wire circles. A bit of flux down the hole and on the end of the rod, pop a circle onto the rod, push it down to where you want the joint and warm up from the bottom, not directly at the flux and solder. In a few seconds, perfect joint, no run except a tiny bit around the hole that forms a fillet.

If you are using the rod, all I can suggest is put the rod onto a hard surface and belt it wiv a big yammer until it looks like a sheet. Cut it into narrow strips (pallions) wiv scissors, and again try to wrap it around the rod going into the hole. If you try to feed in the rod, you are liable to get it everywhere.

There should be an article in the booklet explaining silver soldering.

John

[andyf]

Spuddevans wrote:  Just on the subject of Silver Soldering, and especially to those who have built the Paddleducks engine, how did you stop the silver solder from blocking up the oil hole on the eccentric straps? The oil hole is only about 1mm from the soldered joint for the con rod. Any hints or tips?

Tim, I have read somewhere that typist's correction fluid (Tippex) acts as a resist when silver soldering, but I've never tried it. Might be worth trying on bits of scrap brass to see if it works.

Andy

[spuddevans]

Thanks Bog's, I have both the rod and the fine wire, I was going to use the fine wire in the manner you mentioned, cutting it into little rings. Not having done this before I wasnt sure if the solder would run into the oil hole, but I guess using just one "ring" of solder shouldnt cause a problem.

I have read somewhere that some folks put a very slight chamfer on the hole, I'm not sure why, or for what reason either 

Thanks Andy, I've read that somewhere too.


Tim

[kvom]

The chamfer gives a bit more surface area for the solder to adhere to, esp. if the rod is a tight fit in the hole.

[spuddevans]

The chamfer gives a bit more surface area for the solder to adhere to, esp. if the rod is a tight fit in the hole.

Ahh, That makes sense, thanks Kvom

Tim

[spuddevans]

I got a little more done today on the forks.

I started out by mounting one on a parallel ( that's right, just one parallel as two were thicker than the fork itself ) in the vice and then milling out the middle with a 3mm cutter. I did toy with using a 4mm cutter as that is the desired slot width, but then I remembered reading that when milling a slot, a cutter of a given diameter will often cut oversize when it is cutting on both sides at the same time. Well as you can see, these forks are only 6mm wide and I didnt want to risk making the side walls of the fork-bit too thin, so I used a 3mm cutter and then just took an extra pass across each inner side of the fork to make the slot 4mm with the walls 1mm each.


Then it was on to drilling and tapping. The forks are drilled and tapped thru, M2.5 at the top end. So mounting them in the vice they were centre drilled and then drilled thru 2.1mm. I left them in the vice to tap them, I just wound the x-axis to one end to give clearance and then put my tapping stand next to the vice and swung the arm over to tap the holes. I did this as I dont have a vice for my tapping stand yet, and holding these little pieces by hand would not have worked out so good for tapping squarely.

Then it was time to roll out my latest version of my vice stop.


( by the way, that hold-down is only tightened up just enough to hold the 2 parallels in place, I reckon if it was tightened up real tight the whole lot would not be very stable, but this setup allowed me to have the whole of the fork gripped by the vice while I gently drilled thru for the pin to hold it to the block on the eccentric rod )

After all those shenaninaninanigans  ( drumroll please ).........here is a finished fork. The overall dimentions are 11mm tall by 6mm by 6mm.



And here are both of them with the eccentric assembly's



Onwards and Umm, sideways? 

Tim

[chuck foster]

looking good 

chuck 

[Bernd]

Hey Tim,

It looks like you need to take a bit of time to make yourselve a vise stop. 

Nice job by the way.

Bernd

[spuddevans]

It looks like you need to take a bit of time to make yourselve a vise stop. 

You know what, you could be right, in fact, you are right!! I really do need one, but I want to get on with this build, and nessesesesesety being the mother of invention, I keep coming up with ways to make a temp' vice stop to suit what needs to be done at the time. Lazy I know, but I try to kid myself that I will have a better idea of what I want from a proper vice stop by making up these temporary forms. (well that's my excuse and I'm sticking to it  )


Tim