Author Topic: David Goodfellows - Brassy Babe: My first engine build. (Read 16945 times)

raynerd · « **on:** June 03, 2009, 07:50:21 PM »

Hello

I didn`t want to start this thread until I had something to show you. My other projects are on hold, waiting for funds for my Shumatech DRO and awaiting the belts for my X2 drive conversion. I decided to make a start on my first engine build. I did quite a bit of research and it was a resounding answer that a wobbler is a nice first timer. There were quite a few free plans online, I found Dave Goodfellows - Brassy Babe a nice looking engine but with the main thing being that he also has quite a significant write up with comments to help the build.

http://www.davegoodfellow.com/plans.pdf

I have been working on it since Sunday evening and I was pleased that I could join a few bits together this evening and get some motion. It seems to turn OK. Obviously I presume it is a whole different ball game getting it to run under pressure but I`m pleased that I have got something that moves!! I`m also getting more confident with the mill which I haven`t really used all that much.

I made it all from scraps that I have been accumulating over time, the majority is made from brass or ally. I picked these plans due to the explanation but closer inspection would actually reveal that he is often lacking in dimensions! That was an issue, but it has also made me think about it and add to the challenge. I suppose I`m getting carried away, it isn`t really running yet, I was just thrilled to get it fastened together and it sync up and move!

Next step is to counter sink the screw hole and find a suitable spring to apply the pressure on the cylinder. I will then finish the frame and locate the remaining holes. Then I need to lap all surfaces as, especially the front running surface - I may even try and mill it. Then finally onto the flywheel.

Chris

cedge · « **Reply #1 on:** June 03, 2009, 08:56:33 PM »

Chris
It wasn't long ago (last year) that I was exactly where you are, right now. The mill was a stranger and dimensions were "targets" I seldom managed to really hit. It all taught me to think my way through a project, before, during and after the metal torturing began. Enjoy the feeling of accomplishment and share it with us. We are the people who's eyes don't glaze over when you describe how you do it....(grin). As a bonus, we get to enjoy the feeling we've all felt, all over again.

Steve

sbwhart · « **Reply #2 on:** June 04, 2009, 12:57:02 AM »

Way to go Chris just you wait until you get it running:- grin from ear to ear.

Stew

Stilldrillin · « **Reply #3 on:** June 04, 2009, 02:19:49 AM »

Looking good Chris.

Good luck!

David D

sbwhart · « **Reply #4 on:** June 04, 2009, 03:10:39 AM »

and find a suitable spring to apply the pressure on the cylinder.

Chris a ball point pen is a good place to start, I'm shure you've got plenty of them

Stew

spuddevans · « **Reply #5 on:** June 04, 2009, 04:18:07 AM »

Looks good Chris,

I'm sure you'll have it running on air in no time at all, and I have to tell you that is the greatest feeling

Tim

raynerd · « **Reply #6 on:** June 06, 2009, 04:00:22 PM »

Hi all, any advice welcome - it needs some fine tuning and I am struggling!

OK, well finished off Brassy Babe and unfortunately it isn`t working properly! Not really a surprise to me, but now I`m trying to find out what is wrong. I have hooked it up to the compressor and it is certainly working to a degree - you can certainly see it is gaining something from it!

I feel like it is the flywheel that isn`t creating enough momentum to pull it though the next phase of the cycle. If I turn the whole thing upside down I definitely get a few seconds run time out of it. I also notice that my piston is not uniform and must taper, the pressure is 100% forcing the cylinder up but then the air escapes from it at the top rather than through the outlet!

Any advice as to which to "debug" first - I feel that if I could modify the flywheel to spin more freely it would run as it is right at the top of the crank where it ends up stopping, the flywheel isn`t driving it back around. Then again, is the air escaping from the cylinder an issue, although this is certainly at the top of the cycle at the same point that it would be escaping from the outlet anyway.

Advice welcome. I`m getting some action so i`m not totally gutted.... yet

Chris

sbwhart · « **Reply #7 on:** June 06, 2009, 04:13:49 PM »

Hi Chris

One thing you may try is to get each element running freely, work on the flywheel first get that running free, connect it to the crank get the crank running free round the crank pin, then get the piston running free in the cylinder. Lap each part in with toothpaste or brasso, make sure you've got no tight spots, the smallest burr will have an effect, clean round the edges with a scalpel, these small engines havn't a lot of power so the slightest thing can stop them.

Keep trying it sounds like your very close it took me a couple of days to get my first wobler running.

Good luck

Stew

raynerd · « **Reply #8 on:** June 07, 2009, 07:29:50 AM »

It is running but won`t run properly sat on the stand - even if you just raise the back up a little it will run but if you turn it upside down it really fly around!!!

Any advice as to why it isn`t running correctly the right way up would be greatly appreciated.

raynerd · « **Reply #9 on:** June 07, 2009, 08:10:08 AM »

Well 10 minutes later and it is running

But with an issue

Advice would be greatly recieved...

This video actually exadurates it a little - On the base it won`t run, or 1 or 2 revs max. If you just raise the back up a few mm it runs! Turn it upside down and it flys around!!

Why isn`t it running level on the base?

sbwhart · « **Reply #10 on:** June 07, 2009, 08:46:37 AM »

Where did you get the plans from Australia

Its obviously got something to do with gravity, but what I'm not to sure you could have something out of square, you've also got quite a wobble on the flywheel, you could try taking the wobble out by skimming it up on the shaft, that may help.

Try different pre loads on the spring.

Stew

raynerd · « **Reply #11 on:** June 07, 2009, 08:50:24 AM »

Cheers Stew

I think I`ll remake the flywheel. The hole is a little off centre (my fault

) and causing it to wobble, consequently I think that it isn`t uniform it its motion.

I`ll keep you posted - pleased that it is working at least!!

Stilldrillin · « **Reply #12 on:** June 07, 2009, 11:42:31 AM »

That`s a good un...... Not!

Never seen a wobbler with a problem like that before!

Really intrigued now.......

NO ideas of course!

David D

DavesWimshurst · « **Reply #13 on:** June 07, 2009, 01:45:36 PM »

Chris,
My guesses for the problem are
1 cylinder pivot out of square to cylinder.
2 crankpin out of parallel to shaft.
3 crankshaft bearing hole not perpendicular to port face.
It seems like the weight of the flywheel may be changing the alignment for the better when upside down. Can you see any gap between the port face and the cylinder at any point in the rotation? After it has run a while wear marks may tell how the parts are fitting.

Just guessing but hope it helps.

Dave

raynerd · « **Reply #14 on:** June 07, 2009, 03:28:38 PM »

Well guys, you`ll be pleased to hear it is working!!! hurraaa

Although many issues that have been mentioned are problems related to my engine, I have worked on two things that eventually got it going.

As davesWimshurst mentioned in the last post, the flywheel is too large and when upright is bearing down too much weight on the crank shaft which has too much "give" in the frame hole, causing it to bend down. This little engine is very forgiving and later I will rebuild the flywheel but for now I just spun the flywheel on the crank shaft and tightened it up with the grub screw on the other side. This shifted the weight for the better and now the fact that the cam action of the off-centre flywheel is actually acting to pull the piston back down through the none powered phase of the cycle. This made my engine work.

Second thing I did was to put a bit of grease on the piston, reducing the air escaping from my tapered piston at the top of the cycle. Clearly this was causing a loss in power as this really improved the performance of the engine.

So lots of errors and of course all down to my poor machining - BUT it is running and I certainly have more confidence and can learn from my mistakes for the next one. I am going to spend a little longer on this one - I`ll polish it all up, make a new piston and also turn down the flywheel on a mandrel so that it is true to the centre drilled hole. Certainly very proud of my first runner!

And finally - big thanks to you lot - couldn`t have made it without your advice and help.

Chris

spuddevans · « **Reply #15 on:** June 07, 2009, 04:12:40 PM »

Well done Chris

It's a great feeling isn't it, now you are hooked

Tim

NickG · « **Reply #16 on:** June 07, 2009, 04:43:23 PM »

Well done! My first oscillator was similar, mine was one of the tiny ones with 1/8" bore which didn't help, it needed 40 psi to run, but 40psi also snapped the soft-soldered in crank pin! It did get me hooked though and as you said, plenty of lessons to be learnt.

Cheers

Nick

sbwhart · « **Reply #17 on:** June 07, 2009, 05:11:40 PM »

Well done Chris

What you've learnt with this little engine is invaluable.

They look deceptivly simple, but are more of a challenge to build than meets the eye, you can still learn a lot from it as you tune it.

Have fun

Stew

Darren · « **Reply #18 on:** June 07, 2009, 06:50:15 PM »

Well done Chris, I bet you have learnt loads building this little engine

DavesWimshurst · « **Reply #19 on:** June 07, 2009, 07:41:42 PM »

Chris,
Congratulations on getting it going, it's a great feeling !

It's good to make a lot of mistakes early on so you won't have to ever make them again!

Dave

Stilldrillin · « **Reply #20 on:** June 08, 2009, 02:25:55 AM »

Well done Chris!

The first of many, every one a gem.......

David D

shoey51 · « **Reply #21 on:** June 08, 2009, 02:44:25 AM »

:clap:well done

raynerd · « **Reply #22 on:** June 08, 2009, 02:51:13 AM »

Cheers Guys.... I know I need to polish this one but I`m sat here at the moment planning my twin cylinder based on a similar idea! Definately got the bug

raynerd · « **Reply #23 on:** June 14, 2009, 02:46:43 AM »

I have decided that my work on Brassy has "finished". There are many improvements to make but under inspection, quite literally all the parts could and should be replaced and remade. I`m quite prepared to do that but I feel that I would prefer to leave Brassy as she is, up and runnning, as my first engine attempt and move on to another build, even if it is another Brassy, and implement my knew knowledge.

I wanted to ask for your opinions on something as I am deciding what to build next. I know brassy is a single cylinder and therefore only has power on half the stroke (don`t know correct terminology). I want to make a twin cylinder - If i made Brasy but instead had the frame as a U and put a Brassy at both ends with a flywheel in the centre, syncronised the pistons, would this work??

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Author Topic: David Goodfellows - Brassy Babe: My first engine build. (Read 16945 times)