Roy's Little Engine

[Jo]

Rework??

Who's this judge then?

Obviously I can only assess your workwomenship from your pictorial record but I cannot see anything that might delay a run.

Judge = Eric Offen who judges the stationary engines (amongst other classes) at the MEX and other shows

He complained that the crankshaft was not freely running and it needed honing out and I just had to find an extra long hone to use on smelly to do it  Then that the crankshaft was bent as it was slightly tight at one point more than the rest of the rotation and then the flywheel fit, despite the painted one having very little run out <0.1mm when you put a dial on it and turn the crank ... Wait and see the engine bouncing around as it is running without any balance weights and see if you can see 0.1mm run out on one side of one of the flywheel  then there was the "where are the balance weights".

The crank fit has been honed by putting a bit of oil on another bit of silver steel and twirling it around - so I assume that was some paint in the bore or something. The crank has a 5 hundredths of a mm run out 

So sort out the crank and then play with the flywheels again in the meantime suffer with the boy being rude about the fit. Is it any wonder people don't like to post their engine builds when they see members making such comments about someone else's build, it is really off putting, I hate to think what newbies think about his comments


As Eric so generous mentioned on Thursday: The problem is that all my fits are like a virgin when on an engine often as not should be more like a Whore 

Jo

[b.lindsey]

Maybe akin to food critics, the only thing they find palatable is the critiquing itself. I don't think such judging is as common over here at the engine shows, but I could be wrong. In any case, most of us are in it for the fun and challenge, and not the fame. Once can only hope the newbies are not judged as harshly.

Bill

[Jasonb]

You should not have a problem with no balance weights, quite a few of the open crank engines I have made don't have any, one or two have a bit of a balance weight cast onto the flywheel or you have to mill a bit out but these engines are not running as fast as Erics aero engines so should not be much of an issue.

Try clocking the crank with one end held in a collet as the slight pressure from the tailstock can "spring" the crank back into the position you turned it in and then when taken off it moves.

You do make fairly tight engines as I have mentioned before, with the conrod off you should be able to spin the crank and flywheels for some time but have no noticeable slop

<a href="https://www.youtube.com/watch?v=oTnp2QMo4Dk" target="_blank">http://www.youtube.com/watch?v=oTnp2QMo4Dk</a>

[Alyn Foundry]

Oh, ok....

Alex always said " you can't fit a 5/8" peg in a 5/8" hole " .. In other words a little tolerance is required, fine fitting.

As Jason has already pointed out, check your runout using a collet with the other end of the crankshaft free. This will show accurately any discrepancies. Usually a " smart " rap with a rubber mallet can adjust a few thou!

How's the piston to bore fit? That's another area where a couple of thou makes a huge difference.

Regarding the engine having no ballance weights, ideally we're looking for a running speed of 350/400 RPM. At this speed with a reasonably good mounting plinth you'll not have any trouble. There's nothing stopping you from making a couple of weights that can screw onto the rectangular webs however.

As posted earlier, you're looking for at least a few revolutions freewheeling with the plug out.

Cheers Graham.

[NickG]

Sorry Jo for only finding this just before the best bit!I rarely look for new topics on the forum now as it takes up too much time watching everyone else’s awesome work! It looks great by the way, got my fingers crossed - definitely do a few checks like Jason did with regards to free - running. A fit like Jason’s is definitely going to help it run well, there’s no need for
It to be any tighter, a bit of slop in it shouldn’t hurt too
Much but if it’s too tight it won’t run at all.


Sent from my iPhone using Tapatalk

[Manorfarmdenton]

Jo - you know the definition of an expert?  An ex is a has-been and a spurt is a drip under pressure!  I gave up paying attention to them years ago.  The constructive advice I've had on here is far more use than nit-picking criticism.

My RLE was too tight to run initially, but a session of rotating it with a drill soon got it loosened up.  Slightly slackening the big end nuts helped!  Then it didn't have much compression but more turning by drill followed by running under its own power gradually brought that up.  Now I can start it by hand, so its getting there.  I should have taken a leaf out of your book and painted as I went along - now I've got a lot of messy black-looking oily castings to try to get clean!

John.

[Jo]

Thanks John 

The problem with Eric is he likes everything perfect and runs away with his advice even when you are constantly telling him that you have not done the final fit yet or yes you know that needs doing  He is a very useful person to make comments on an engine and unlike others does not seek to score points by being rude about your efforts. Trying to capture all of it (and stop him dismantling your engines one after another ) in time is a bit more tricky.

Oily castings are difficult to get paint to stick on 


For the picky one: the crankshaft WITHOUT a flywheel if given a flick spins for 4 rotations before coming to a halt. If you put a HUGE flywheel on a little crank then give it a flick... surprise, surprise it goes round and round for a long time. As I mentioned previously I am not happy with the flywheel fit but unlike him I am honest enough to admit to my failures. Eric and I have investigated and identified why the bore went slightly oversized.

Jo

[Alyn Foundry]

Hi Jo.

Well that's good news regarding 4 revolutions of the crank without flywheels. 

How easy is it to push the piston up the cylinder? You shouldn't need too much pressure.

Cheers Graham.

[Jo]

How easy is it to push the piston up the cylinder? You shouldn't need too much pressure.

Wait for it, wait for it.... Currently the silky fit means that it would probably run without rings.

I have still to get out and make the cam to go on the crank, which had been next on the list but I seem to have wasted ages measuring the crank as it is springing all over the place. I'm off to play with some castings that are sitting on the dining room table

Jo

[Jo]

Oiler in place 

Jo

[Jasonb]

Getting closer to  time

[Alyn Foundry]

Getting closer to  time

Hmmm, perhaps not....

There's no oil in it !!   

[Jo]

Getting closer to  time

That's Thursday if I bring him back another set of castings.

Work continues... mainly gardening ( which never seems to end ) and house maintenance  Its at time like these I think how nice it could be to have a handyman around the house to do things for me 

Jo

[Jo]

After messing around on Mr Silky trying to get the flywheels true to bore out the centres for the bush by holding on the inside of the rims I gave in and wandered over to Big C and put them in his three jaw using the outside jaws. A quick spin of the chuck with a dial on the rim proved that the chuck holds true  The old repair bushes were bored out of both flywheels and a new set of top hat shaped bushes machined and fitted using Loctite.

Two days later back in Big C's three jaw both were bored out to be a tight fit on the crank. From the rim side of the repair bushes the broach was passed through and finally Big C took both faces of the centre of the flywheel down to width.

Next I need to splodge a bit of paint on that other flywheel  but there are still flower beds to plant up 

Jo

[Alyn Foundry]

Hi Jo.

Can you confirm that the keyways in the flywheels intersect between the bushes and the parent metal?

I'm more than a little concerned that if you're relying upon the adhesive to hold the bushes solely you'll have a couple of minutes running before the shock breaks them.

My comments are based upon actual experience.

Cheers Graham.