# Going to build my first engine!



## clevinski (Jun 17, 2014)

Hi, All,

After lurking for a while, and gaining some more machining experience, I've finally decided I am going to attempt my first, small model engine.  For a first attempt, I want to keep it as simple as possible, and thought I would go with a wobbler.  I found plans from Western Kentucky University for what they describe as a "Lucy"-style wobbler.  Any comments regarding whether this would be a good first engine project?  It seems simple enough.

I recently read someone's comments on another member's design where two things were pointed out that seem to be lacking here.

First, this design seems to omit any packing.  Is that an issue here?

Second, the piston lacks any spacer to keep it a fixed distance from the crankdisk and thereby prevent any side forces which could increase friction between piston and cylinder and accelerate wear.  Perhaps this isn't an issue because the piston is the same diameter for its full length?

Anyway, I am looking forward to working on my first engine, and want to thank everyone here for the education I got reading your posts!


----------



## crueby (Jun 17, 2014)

Hi Charlie,

On a wobbler, the end of the crankshaft usually just 'floats' on the crankshaft, finding its own position since the piston holds it in place horizontally. Even on a more complex engine the same is essentially true. It is important to get the crank pin as square to the crankshaft as possible - if it has an angle it will torque the piston back and forth.

There is no packing, it depends on a nice close sliding fit of the piston in the cylinder bore, and a smooth surface of the cylinder on the plate along with the spring to hold pressure.

Good luck on your first engine!


----------



## vascon2196 (Jun 17, 2014)

Charlie...I have built about a dozen of the "Lucy" style engines and have had my students build them each semester for the past 6 years. This engine is perfect for a first time engine. It has very little parts, can handle tolerance errors, and gives the builder the ability to make changes on the fly.

Here is an article I wrote in Digital Machinist Magazine a while back.

Thew original plans can be found online...Lucy the See-Thru engine...because it was made from Lucite (clear acrylic).

http://www.neit.edu/blog/wp-content/uploads/2013/02/Vascelanos.pdf


----------



## clevinski (Jun 17, 2014)

Crueby, Chris,

Thanks for the suggestions and information.  BTW, I love the transparent cylinder!


----------



## Tin Falcon (Jun 17, 2014)

that would be a fine choice  for a first engine. 
no need to worry about side loads or packing. you can always ad a washer or spacer if you like. 
My lucy has probably ran a few hundred hours at this point had it over ten years, 
Tin


----------



## robcas631 (Jun 17, 2014)

Vascon, Excellent article!


----------



## BronxFigs (Jun 18, 2014)

Just as an alternative...check out the "Little Husky" steam engine.  Also a very simple, bar-stock design.


Frank


----------



## clevinski (Jun 18, 2014)

Thanks, Tin!

Frank, the Little Husky looks like a great retirement project, but I think, with my limited machining expertise, I am going to start with the simpler Lucy.  But I see a Little Husky in my future! Thanks for mentioning it...


----------



## Tin Falcon (Jun 18, 2014)

The 

McCabe Runner

Is another easy fun one.
Tin


----------



## clevinski (Jun 19, 2014)

Wow... That McCabe Runner is really old school!  Thanks for suggesting it...


----------



## Tin Falcon (Jun 20, 2014)

You can make them in clear plastic as well here is one of my Builds from the McCabe plans. 








Have fun 
Tin


----------



## clevinski (Jun 21, 2014)

Tin,

Beautifully done!


----------



## clevinski (Jun 22, 2014)

Hi, All,

I have a couple of what are probably newbie questions, and I'm hoping I can get some advice here.

First, the Western Kentucky University wobbler plans specify a bronze bushing for the crankshaft where it passes through the valve plate.  Does this really need to be bronze, or can I turn a brass bushing for this purpose instead?  I was thinking of turning it from brass, pressing it in place, and then drilling an oiling hole from the top to allow lubrication to get into the running surfaces, but maybe that's overkill.

Second, I read in a post somewhere that one should select materials so that running  surfaces were always dissimilar materials.  This can lead to some oddball  combinations.  For example, I am going to  make the cylinder out of aluminum, since I have material about the right size.   The piston can then be either brass or steel, both of which I have, but if its  steel, does that mean that the mating crankdisk pin would then have to be  something *other* than steel?  In my limited experience with loaded moving parts, running parts are often steel on steel but lubricated.  Another  issue; the valve plate in the plans seems to be aluminum, and the cylinder seems  to also be aluminum.  Since these two surfaces are held in contact with each  other during operation, but they are like materials.  Would this be an issue?  I assume that the "like on like" restriction is intended to prevent the wear from occurring equally on two parts, but I'm not sure if there's more to it.

Many thanks in advance for any comments...


----------



## Swifty (Jun 23, 2014)

Hi Charlie, with a wobbler a brass bush would be no problem. The problem with similar materials running on each other is galling. In my opinion you would have no problem making a wobbler out of the same material, there is not a lot of load or speed involved, and I doubt if the speed would warm up any parts.

Paul.


----------



## Tin Falcon (Jun 23, 2014)

Do not worry too much about correct materials. These rules of thumb are best practice for working engines. 
And remember you do have a shop if a part wears you can make a new one. 
you can always put a brass tube sleeve in for the cylinder bore. in an aluminum block . I did that for my McCabe runner. (the first one. 
cylinder to frame we often beak the rule and use like materials. 

In engines that actually run on steam or in a pump galvanic corrosionfactors needs to be considered. 
tin


----------



## clevinski (Jun 23, 2014)

Paul, Tin,

Thanks for the valuable input!


----------



## clevinski (Jul 2, 2014)

Hi,

Anyone know where I can obtain the barbed hose fitting and hose used to connect my air supply to the wobbler?  I could make one, but the effort seems disproportionate to the result if I can get one locally.  Is this maybe something from an aquarium store?

I finished the piston (very easy) and am almost done with the cylinder.  I was, perhaps, overly cautious when clamping the cylinder to drill the bore; photo below.  (In my preview, this image keeps coming out inverted, but the original is fine.  Hopefully it's just an issue in the preview...)

I got the missing base plate and valve plate material from Exact Metals.  Total of $16 for two aluminum plates 1/2" x 3" x 6" and four pieces of 1/4" steel rod 12" long, INCLUDING shipping.  I think these guys are my new favorite metal supplier!


----------



## clevinski (Jul 2, 2014)

Hmmm... Apparently it's NOT just an issue with the preview...


----------



## vascon2196 (Jul 2, 2014)

I sometimes use quick-disconnect fittings from McMaster Carr or any #10-32 air fitting for my air engines.


----------



## clevinski (Jul 2, 2014)

Thanks, Chris...


----------



## Swifty (Jul 2, 2014)

Charlie, what did you used to take the picture with? I have had trouble in the past because I was taking pictures with my iphone, if I am going to post pictures from the phone, I have to be careful of the orientation when taking them. I save my posted photos on photobucket, I rotate to the correct orientation, but they revert back to upside down when posted. I did google this problem, and there were a few ideas to fix it.

As far as barbed hose fittings and clamps, I never have to use them. The maximum pressure I use is only about 15lb, no enough to blow the hose off a straight fitting. Most engines will run on about 5lb - 10lb if all friction points are reduced.

Paul.


----------



## gus (Jul 3, 2014)

clevinski said:


> Thanks, Tin!
> 
> Frank, the Little Husky looks like a great retirement project, but I think, with my limited machining expertise, I am going to start with the simpler Lucy.  But I see a Little Husky in my future! Thanks for mentioning it...




Lucy is a very forgiving engine to built. Was my very first engine. The inlet and exhaust ports must be aligned to get good spin. Slight misalignment is forgivable.


----------



## clevinski (Jul 3, 2014)

Swifty said:


> Charlie, what did you used to take the picture with? I have had trouble in the past because I was taking pictures with my iphone, if I am going to post pictures from the phone, I have to be careful of the orientation when taking them. I save my posted photos on photobucket, I rotate to the correct orientation, but they revert back to upside down when posted. I did google this problem, and there were a few ideas to fix it.
> Paul.



Paul,

I think you hit the nail on the head.  I took the photos with an iPad mini.  It is my first Apple product and I've only had it a few months.  I will have to pay more attention in the future and flip the photo in a photo program before posting, if necessary.

Re the fitting, I guess my issue is really where to get ANY such fitting, barbed or not.


----------



## Swifty (Jul 3, 2014)

Small air line fittings are available from pneumatic valve suppliers like Festo, I think that the smallest thread was M5. But I just usually make mine from some brass.

Paul.


----------



## clevinski (Jul 4, 2014)

Swifty said:


> Small air line fittings are available from pneumatic valve suppliers like Festo, I think that the smallest thread was M5. But I just usually make mine from some brass.
> 
> Paul.



Hi, Paul,

Thanks... I should have realized that, as my employer is a long time supplier to Festo!  :wall:


----------



## rodw (Jul 4, 2014)

On my first engine (an EZ runnner) which is what got me to this forum initially, I had some aluminium tube which I think was the spout off a cheap oil can so I just pressed it in.  No barbs are required at the pressures involved. I poked the end of my air duster in one end of some hose and the engine into the other. That held enough to get up to about 8000 rpm....


----------



## clevinski (Jul 4, 2014)

rodw said:


> On my first engine (an EZ runnner) which is what got me to this forum initially, I had some aluminium tube which I think was the spout off a cheap oil can so I just pressed it in.  No barbs are required at the pressures involved. I poked the end of my air duster in one end of some hose and the engine into the other. That held enough to get up to about 8000 rpm....



Hi, Rod,

Thanks... Seems like maybe I am making too much of it...


----------



## clevinski (Aug 14, 2014)

Hi, All,

Well, I just finished machining and assembly of my Lucy-style wobbler this afternoon.  I didn't chase down the air fitting yet, so I just held my air gun against the intake opening where the fitting would thread.  I got half a turn, and then nothing.  After numerous repeats, I realized that there was a little binding going on in a few spots, so I corrected them.  (Opened the hole slightly in the piston and polished the crankshaft further to reduce it's diameter.  In spite of being really careful to drill the crankdisk square, and making a little fixture to make sure it went in square when I pressed it in, it was still a bit off.)  Now it makes about 1 3/4 turns but won't continue.  I guess tomorrow I'll rig up the air properly so I can take some pictures/video while it's failing to run.

The one big variable is the spring.  I tried to use a spring about the same wire diameter and spacing as the original plans, but whether I succeeded is anyone's guess.  To compensate, I bought screws of various lengths so I can use them to adjust tension.

BTW, these original plans from Western Kentucky University have a few errors.  There were numerous missing dimensions, most of which could be calculated from the other parts, but one of which could not.  (This was the horizontal position of the crankshaft hole in the valve plate.  I ended up scaling it from the drawings.)  There were also some errors (wrong drill size specified for tapping a 10-32), and some things that I would have done differently (for example, using 10-32 threads for strength in aluminum.  I would have specified a coarser thread, but this is a moot point since that was the wrong drill size issue [yes, I should have checked it myself BEFORE drilling] and I ended up going to 1/4-20.)  I mention all this primarily in case someone else is using the plans.  They were free, they were clear, and they got me started, so I'm glad they were available.

I'll post some photos/video tomorrow, and then maybe those of you with more experience than me (i.e., everyone on the site) can feel free to make suggestions...


----------



## clevinski (Aug 14, 2014)

Hi...

I am posting some not so great photos below.  I plan to add an air fitting tomorrow for a better test.  Any comments welcome!


----------



## vascon2196 (Aug 15, 2014)

Looks great...nice and clean looking.

Careful, when you get this running you will be hooked!

Save your pennies!


----------



## clevinski (Aug 15, 2014)

vascon2196 said:


> Looks great...nice and clean looking.
> 
> Careful, when you get this running you will be hooked!
> 
> Save your pennies!



Thanks, Chris...

I got a fitting installed and I can get about 20 turns out of it.  If I "help" by adding some speed to the flywheel, the motor will gradually slow down and stop.  I assume that this means I am losing energy to friction, so I need to recheck the crankshaft for binding tomorrow.  Hopefully that's the only remaining issue...


----------



## Jyman (Aug 15, 2014)

What is your flywheel made out of it?


Sent from my iPhone using Model Engines


----------



## gus (Aug 16, 2014)

vascon2196 said:


> Looks great...nice and clean looking.
> 
> Careful, when you get this running you will be hooked!
> 
> Save your pennies!




I standby Chris. Gus is terribly and hopelessly hooked and went on to bigger
addiction(I.C. Engines). :wall::rant:


----------



## clevinski (Aug 16, 2014)

Jyman said:


> What is your flywheel made out of it?



Jyman,

It is made from "free-machining", leaded steel.  The main body of the flywheel is 3" in diameter, and it's 1" wide.  The drawing calls for a piece 1 1/4" wide so that a 1/4" wide collar can be turned for the set screw, but I only had a 1" thick blank.  So I turned a piece of 1" with a 3/4" diameter, 1/4" thick shoulder, bored the main flywheel and pressed them together.


----------



## clevinski (Aug 16, 2014)

clevinski said:


> I got a fitting installed and I can get about 20 turns out of it.  If I "help" by adding some speed to the flywheel, the motor will gradually slow down and stop.  I assume that this means I am losing energy to friction, so I need to recheck the crankshaft for binding tomorrow.  Hopefully that's the only remaining issue...



So, I got it working! I needed to reduce the end play on the crankshaft and polish it to get the diameter down a bit, add a few strategically placed drops of oil, and then it ran fine.  Well, I guess it's running fine.  It takes it a while to build up to speed.  I assume that's normal since it has to accelerate the flywheel. I checked one of the early runs and was reading 1300+ RPM with an optical tachometer; it seemed to be faster in some later experimenting but I didn't measure it.  I made a video with an iPad, but I am having a bit of a challenge uploading it.  I'll post a link when I do...


----------



## clevinski (Aug 16, 2014)

Finally... I got the video uploaded!

You can see it here...  (I hope... at least I can see it here when I go in from HMEM...)


----------



## vascon2196 (Aug 17, 2014)

Way to go dude...keep um coming!


----------



## clevinski (Aug 17, 2014)

vascon2196 said:


> Way to go dude...keep um coming!



Thanks, Chris!  I learned a lot building this, even though it is incredibly simple and forgiving compared to some of the others that people have posted here.  So I need to start thinking about the next one... something simple, but maybe a bit more complicated than the wobbler...


----------



## weez (Aug 18, 2014)

clevinski said:


> So I need to start thinking about the next one... something simple, but maybe a bit more complicated than the wobbler...



Excellent looking and running first engine.  For your next one I would suggest one of Elmer's engines.  There are lots to choose from and many are good for beginners.  I have built six of them so far with more to come.  Plans can be found at http://www.john-tom.com/html/ElmersEngines.html.


----------



## clevinski (Aug 19, 2014)

Thanks, Weez,

I'll check out Elmer's page!


----------



## clevinski (Sep 10, 2014)

Hi, All...

So... I was a bit unhappy with the loose fit of the crankshaft on my Lucy air motor to the bronze bushing. For some reason, it rapidly became too loose, even with only 15-30 minutes of total run time. So I thought, before I moved on to a new motor, that I would resolve this by replacing the bushing with a needle bearing; this one: (SCE47 1/4"x 7/16"x 7/16" inch BA47ZOH Miniature Needle Bearings BA47Z ).

I drilled and reamed a 7/16" hole to mount the bearing and pressed it into place. The press fit went well; it required some force on the arbor press, but not what I would consider an excessive amount. I then cut a piece of 1/4" diameter drill rod (which measured 0.2510 inches in diameter) to act as a crankshaft. To my surprise, the drill rod was a loose fit (by a few thousands, I would estimate) in the bearing. I can machine a stepped crankshaft to get the right diameters, but I don't understand why the oversized drill rod is loose. Can anyone shed some light on this?


----------



## Cogsy (Sep 10, 2014)

I worked for SKF for quite a few years and I can only guess that the bearing you bought is a 'cheapy' maybe? The tolerances on bearings are very tight and I wouldn't expect an oversize shaft to fit at all. I have some chinese ball races I bought a heap of (skate board size) and their bore sizes do wander around a bit.

Your needle roller is designed to run on either an inner race (which you can buy separately but you'll need a bigger bearing) or a hardened shaft. Your shaft may not last long if it's not hardened.


----------



## clevinski (Sep 11, 2014)

Cogsy said:


> I worked for SKF for quite a few years and I can only guess that the bearing you bought is a 'cheapy' maybe? The tolerances on bearings are very tight and I wouldn't expect an oversize shaft to fit at all. I have some chinese ball races I bought a heap of (skate board size) and their bore sizes do wander around a bit.
> 
> Your needle roller is designed to run on either an inner race (which you can buy separately but you'll need a bigger bearing) or a hardened shaft. Your shaft may not last long if it's not hardened.



Hi, Al,

Thank you for the reply and the information.  I bought the bearing from a storefront on eBay, and I assume they are a cheaper brand, so that is probably the issue. I am just surprised at the dimension; if I had to guess, I would say the shaft needs to be .255" or so, which is WAY oversized.

Regarding the shaft, I realized after ordering the bearing that the shaft would need to be hardened.  Since my little wobbler doesn't DO anything, it will see very little use, and I can always replace the shaft, if necessary.


----------



## bouch (Sep 11, 2014)

weez said:


> Excellent looking and running first engine.  For your next one I would suggest one of Elmer's engines.  There are lots to choose from and many are good for beginners.  I have built six of them so far with more to come.  Plans can be found at http://www.john-tom.com/html/ElmersEngines.html.



There are a lot of great engines there.

His #33 is quite popular.  That would be a good choice if you want to tackle something more challenging than a simple oscillator.

If you want another oscillating engine, then I would suggest either "Fancy" (#15) or "Wobbler" (#25).  I've built Wobbler, nice little project.

Engines to avoid for a 2nd project, IMHO, are "Geared Steam Engine" (#5) and "Kimble Engine" (#20).  Those require VERY careful tolerances...


----------



## clevinski (Sep 12, 2014)

bouch said:


> There are a lot of great engines there.
> 
> His #33 is quite popular.  That would be a good choice if you want to tackle something more challenging than a simple oscillator.
> 
> ...



Bouch,

Thanks for the advice... I am definitely not ready for VERY careful tolerances!


----------



## gus (Sep 12, 2014)

Tin Falcon said:


> that would be a fine choice  for a first engine.
> no need to worry about side loads or packing. you can always ad a washer or spacer if you like.
> My lucy has probably ran a few hundred hours at this point had it over ten years,
> Tin



Hi Tin,

We all grew up with '' Lucy''  .Was among very first few engines.


----------



## gus (Sep 12, 2014)

clevinski said:


> Bouch,
> 
> Thanks for the advice... I am definitely not ready for VERY careful tolerances!




Hi Clevinski,

No worry. As you go along,you get to improve you machining skills.
Getting to print dimension will eventually happen.If a part is undersized,machine another piece. 

Every engine project will demand new skills or higher skills.

High Speed Cutting tools are best to get to spot on O.D. or I.D. Properly sharpened and honed HSS Cutters can remove minute thick metal.I seldom use carbide cutters.

Mark out,centre punching and spot on drilling are skills that need constant practice. Practice makes perfection.


----------



## clevinski (Sep 14, 2014)

gus said:


> Practice makes perfection.



.......... Thm:


----------



## bouch (Sep 15, 2014)

clevinski said:


> Bouch,
> 
> Thanks for the advice... I am definitely not ready for VERY careful tolerances!



Don't worry.  Nobody is when they first start out!  The more stuff you make, the better you get.  I don't want to think about how many pieces I've made at least twice!

Heck, when I build my "wobbler" a few months ago, I build the main body 3 times before I got one what wasn't ruined...


----------

