Finger engine

[Sprocket]

Just for comparison, here is another version. This one was in HSM, but I think they handed out the plans at NAMES one year.

they do make great desk toys.

Doug

 

[Bogstandard]

Unwanted gone, managed to get back in the shop to finish off these damned cranks.

As I said, I am silver soldering mine, mainly because I love silver soldering, and if you can master it, the world of little engines gets a lot easier. Rather than having to pin or screw something together, you can make a much neater job by soldering.

This is the start of getting the job done. The flux (Tenacity 4A) is mixed with water and a drop of washing up liquid to a consistency of pouring cream. If kept in a little sealed container it will last for months in this state.
I am using Easyflo solder, but in the form of thin wire (0.5mm). This is wrapped around the crankrod to form a spiral, just like a spring, then it is cut along the edge to give me a load of little rings.
Cleanliness is paramount to getting a good join. Degrease first then clean it with either carpenters wire wool (no protective oil) or a scotchbrite pad and handle the parts as little as possible.
The way I assemble is to paint a bit of flux into the holes and then push the rods thru, then paint a bit more flux either side of the holes. Then just pop a silver solder ring onto the outside joint where the rod enters the web. This will allow the solder thru capillary action to fill up the joints.

This shot shows the assemblies mounted onto a makeshift hearth made from a couple of firebricks. Only three small rings of solder have been used on each assembly.
I will solder each one in turn. This is really only possible because of the flux that I use, it is designed for mainly stainless but the main property is that it can withstand extended heating without breaking down. With borax you would be lucky to get one done.
I started by playing the flame onto the front left one, between the two main webs, this allowed the heat to go into the blocks and travel along the shafts. About twenty seconds later the solder melted and was sucked into the joint, during this operation the rear set was being warmed up. I then did the front right using the same method then quickly dropped onto the back one which was almost up to temperature and only took a few seconds to complete.
They were allowed to cool down for about a minute then dropped into quench water, which knocked off about 90% of the flux. The flux I use is very aggressive, and if left for too long on non ferrous parts it will eat into them (I am talking about hours, not minutes).
Because most of the flux was removed I decided not to put them into a citric acid pickle bath.

Here they are straight out of the quench, nice clean fillets and good penetration thru the joint. Cut out the unwanted bits and onto the lathe for dressing up.

One finished, two to go.
You need to be aware that a built up crank like this, with a grub screw to allow assembly of the conrod is in fact unstable, and might need a bit of resetting of the grub screw and webs to get it running true, but usually no problems are encountered. I usually hang the conrod down into the vice jaws, push the two webs down onto the tops of the jaws and tweak up the screw.

This is a quickie sketch of the dimensions of my crank webs.

That is the hard part done. Just the conrod and finger doo-dah and then it will be baseplate and assembly time.

BTW, now that I am over half way thru I will tell you why I have done this posting.
I am looking to do a build of an engine like my poppet valve one, only a little more simple, and a lot more machining techniques explained. I have been following this post to see what people have to say and how many questions are asked, plus how many 'spoiler' posts are put in here.

It has been very enlightening. Very few questions asked (just as though everyone knows what I am on about), a few little spoilers and a few comments. Not what I was expecting at all. Will have to see when it is finished in a few days time.

John

 

[dparker]

Hello All: Well, all this talk and Bog's write up about finger engines made me get mine out today. I hooked it up to my homebuilt tach (from Popular Science plans) and had the wife take a picture. She started laughing so much she couldn't keep it running in the same direction long enough to get her picture running it and show the needle off the peg. I can only get it running about 50+ RPM before I get my finger twitchy and reverse it or stall it. I did build it with ball bearings so it run easily (and reverses easily). I did grind up a tool for making the indentation cuts on flywheels from Bo'gs posts and will be trying it out on the flywheel of the "Miser" I am starting. Such small parts! Yikes!

As you can see (I hope) it is running about 30 RPM.
Don

 

[Powder keg]

Fun, Fun, Fun:O)!

 

[Bogstandard]

All my bits working again, so lets get on with it.

These are the basic dimensions of the conrod, and needs to be made like this first. That is if you want to make it out of the solid, there is nothing stopping you from from building it up, but if you go that way you must look at the dimensions on the sketch for the finished rod, coupled with the hole centres on this one.

This is the rough cut plate, about 3/16" over dimensions to allow for machining.

Brought to size and drilled. A real classy looking conrod, about as acceptable as a cowpat in the middle of your lawn.

This pic shows that a same sized rod in each hole and resting on the vice jaw tops gives a nice taper to the rod. Just machine down to the depth you want, flip over and down to the same depth on the other side.

This is my pair of rods, brought to the dimensions of the following sketch, just need a good flatting down and a polish.

This shows the dimensions you need to end up with for the blocks on the ends of the conrod, what is between them is up to your imagination. In fact they don't need to be square, the only critical dimensions are the widths of the blocks. I will be basing all my further dimensions on these figures.

John

 

[Powder keg]

I like how this is turning out. Where did all the pictures go?

Wes

 

[deere_x475guy]

I think Bogstandards pic host is down.

 

[deere_x475guy]

I think Bogstandards pic host is down.

Actually I just checked and he is using Photobucket...this album is showing empty...????

"There is no content in this album."

 

[deere_x475guy]

I just checked the board and it shows he hasn't posted anything in 3 days. Which seems pretty odd for him. Maybe he is on vacation.....still doesn't explain the empty Photobucket folder though.

 

[Cedge]

Bogster PM'd me in a panic late last night. He's managed to screw up his photobucket account and is more than a little worried everyone is going to be upset with him. John is taking a break to deal with some important real world issues. Once he's done, I think we'll probably see his ugly mug again.

I've got a plate full of real world stuff myself and won't be on the board as often either, at least for a while. I'll be lurking and reading, but that's about all that time is going to allow for a while. With the level of talent present on the board these days, I'm sure no questions will suffer for a lack of a proper response.

Steve

 

[shred]

Upset? He could go delete everything he's written and the net benefit would still be more than the annoyance to me (not that I am suggesting such a thing, of course. Skipping the 'annoyance' part is a good thing.. )

 

[Cedge]

Shred
I couldn't have said it any better. John has been a wealth of information and many have benefited greatly from his timely tips and techniques. Myself included.

Steve

 

[Bogstandard]

Now that I am a bit more mobile again, and have managed to get the piccies back for this post (I checked in my camera and they were still there, plus I had the sketches I did).
There is one error on the first sketch I did, the height of the angle should be 1 7/16" rather than 1 9/16".

Once I am under full control again, I will carry on with this post if the interest is still there.

John

 

[Brass_Machine]

Now that I am a bit more mobile again, and have managed to get the piccies back for this post (I checked in my camera and they were still there, plus I had the sketches I did).
There is one error on the first sketch I did, the height of the angle should be 1 7/16" rather than 1 9/16".

Once I am under full control again, I will carry on with this post if the interest is still there.

John

John,

Glad to hear you are mobile again. But never you worry, there is plenty of interest in the finger engines. I am thinking of making one of these for my boy (7 yrs old) when he comes to visit me in 2 weeks.

Eric

 

[Powder keg]

Hey John,
Glad your doing better:O) I'd like to see how it turns out.

Wes

 

[Bogstandard]

Got the motor started and just hope I don't run out of gas before we get there.
What I am going to do, which will be the best way for me, is get the engine built and finished, then do all the measurements and sketches, rather than guessing.

I've been busy the last couple of days and really got on well. I am not going to show you how to profile the bits (except for the baseplates) because you might not like the shape I have made, that is why I am only giving fixed dimensions. You then make them whatever shape you want.

Here is what I made the fingery thingery out of, a lump of drawn ali angle out of an old commercial printer. It was black anodized, just what I always wanted, not. I cut the extra just in case the anodizing removal technique didn't work.

This one shows a couple of stressful hours later, sash weight skin isn't a patch on this stuff. I only had a few thou extra to work with, so by using a flycutter and an endmill for the internal radius I managed to get thru it, and also brought it to size and general shape.

I have already done a bit of profiling on some of the other bits, plus a bit of polishing. So I thought I would make the baseplates. Because this engine is only one fingerpower, I decided a chunky baseplate wasn't needed, so I went for 1/4" thickness, but two of them (for two engines).
This bit should be in the tips section but what the hell.
I stuck the two plates back to back with double sided tape, and machined them to size.
When I profile the edge of plate I love using a 1/4" ball mill, it might be me, but I just like the effect it produces, but not the rag tag surface finish that you usually get with this type of cutter. This is where my tip comes in. When you usually buy a round file it is tapered along it's length, this is to allow you to make all sizes of radii with it, I want one that is parallel along its whole length. So I buy chain saw files in the diameter I require to match the ball cutter size, and cut the tang off (so you don't hurt yourself, or the job), it is then placed in the groove and rubbed along the groove using a bit of lube as well. You will find that within a couple of minutes you will have a nice uniform recess ready for polishing with a bit of wire wool.

This next shot shows the plates unstuck with edges polished and over four hours of engine turning later. It would have been less if I hadn't made a mistake on one about 2/3rds thru. The dog learned a few new words and the cat learned to fly, with a boot up its a**e.
It's starting to look like what I envisioned, classy, with a bit of street bling.

This is as far as I have got by this evening, most bits polished and ready for assembly.
Please note that I am building these engines for a couple of very good friends, so I want them hopefully to be passed onto their children and beyond. So I have lined the bearing holes with brass tubing to give a longer lasting bearing surface, you don't need to do this, but it will make the engine a lot smoother running and longer lasting.

Just the flywheels to get looking something like and a few special bearing pins to make, then cut up the bit of wood underneath (no idea what it is, wood isn't my speciality) to make a couple of plinths and we will be cooking with gas.

John

 

[Kactiguy]

John, this is looking fantastic. It just keeps getting better and better. Can't wait to build one too (if my skills are up to the challenge). Really glad you are back.

 

[Powder keg]

That is looking great!!! I like how you profiled the treadel.

Wes

 

[wareagle]

Bog, as always, supurb craftsmanship! I love the engine turned bases. Very classy!

Your post had me laughing with the bit about the animals learning to speak in tongues! Been there myself a few times.

 

[defarijf]

I love the look of the base plate, I cant wait to se it finished. I might see if can bulit it myself

Joe