Thread: SloMo Wobbler

Originally Posted by arose62

Hi Dave'H,

when I read your post, it appeared to be a random posting of something you'd found on the net - nowhere did it say that you had made it. If I hadn't started to attempt to begin to have a go at a wobbler, I wouldn't have bothered to read further, and halfway down the page notice that it's your own craftmanship on display.

I think that if you had opened with "Look at what I made", then the responses would have been much different, and probably more positive.

I like it, I agree that the flywheel's elegant, I wonder about the grooves on the piston, and I wonder do you know anything about Cape Town's Town Hall (which my grandfather is supposed to have been involved in building).

Cheers,
Andrew

Another local guy Andrew, Col lives down your way, he started a thread on the first page about CNC end mills.

Dave

Hi Dave,
Lovely work and welcome to the forum. I hope you'll find the majority of us Aussies are friendly and helpful.

I wish I had the skill and patience to make something like that. I'd have to replace a lot of window glass before I managed to complete something like that. Out of interest, how many hours do you reckon you spent making it?

Regards,
Chris

Originally Posted by Dave'H

Thank you Pete, Ewan, Dave, Matt, Stuart, for you nice words

Running on air about 1.8 psi - any lower it doesn't run.


Dave'H

That would indicate a bloody nice fitup.

Years back I had a class make an air powered reciprocating engine as a vehicle to encourage student precision lathe work. The kids that got them running had a contest.

Part 1 outright revs
Part 2 the lowest air pressure it would run on.

The regulator on our compressor only went down to around 10 psi and most would not run on that.

1.8 Psi is a really good outcome.
congratulations

Grahame

Originally Posted by jack620

Hi Dave,
Lovely work and welcome to the forum. I hope you'll find the majority of us Aussies are friendly and helpful.

I wish I had the skill and patience to make something like that. I'd have to replace a lot of window glass before I managed to complete something like that. Out of interest, how many hours do you reckon you spent making it?

Regards,
Chris

Hi Chris,

Thanks for your kind words and the welcome
Everyone is friendly. Just a silly misunderstanding that's all.


Oh dear this is embarrassing, Well it took me about 3 months, on and off designing it. Then when I started to make it I thought I would make it upside down (so to speak) just for the heck of it.

To make it about 15 hours spread over about 2 weeks. I kept on changing my mind, and the design. That 15 hours doesn't include all the whoops!, bits I made didn't like and made them differently.

If one includes everything I would say 30 hours.

Bear in mind, I'm normally quite slow when I do things like this, I stop have a fag, cup of tea, biscuit, talk to the dog, watch the cricket. Especially when we are beating the Aussies

No rush for me

Dave'H

Hi,

One of the ideas behind this engine was to make it run on breath power.

My son and a few others can, I can't - I just go dizzy and fall over

Dave'H

Originally Posted by Dave'H

Hi,

One of the ideas behind this engine was to make it run on breath power.

My son and a few others can, I can't - I just go dizzy and fall over

Dave'H

LOL, I do my projects in a similar time frame with many stops for the same reasons, after all it's hobby so we are in the shed to enjoy our time, not to rush to the end.
I also often get side tracked on other jobs on the way through, and after woods wonder how I came to be working on what ever it is.

Thanks for the explanation on the engine and the extra photos. This may look like a really simple engine to build, but the skill in the fitting and machining would show in the end with the amount of psi needed to run it as you have done. Great work.

Dave

Originally Posted by Dave'H

A few photo's showing the ports (holes)






There isn't an awful lot to it.

Dave'H

Thanks for posting the pics of the inner workings Dave
I can't see any seal between the cylinder body and the main housing, I would be guessing that there isn't other than the two mating surfaces coming together well enough to prevent/slow down any air leaks, maybe just a smear of oil is all it needs? also does it require a push start to get it going if the inlet port isn't lined up when it last stopped.
Once again good job


Pete

Pete,

Like you say it relies on the two mating surfaces and a smear of light oil.
Therein lies most of the problems, it is always a trade off between getting a seal and the friction between the two surfaces.The spring on the screw provides the holding force.
There is a round recess that reduces the surface area which helps to reduce the fiction.

It always need a flick of the fly wheel to get it going at about 2.5 psi, after 30 seconds of running I can turn the psi down. There is no power at the flywheel, there is just enough energy to over come all the fiction and lift the piston against gravity.

I can over come the effect of gravity on the piston by turning the engine upside down, and a slight increase in speed can be noted, it will run on a slightly lower psi when run upside down.

So long as it goes round the grand kids luv it

I would like to say they are a lot easier to make than it appears.
If the seal isn't too good use some more oil, increase the spring pressure and turn up the air pressure - it will whiz round I'm always of the opinion "if one uses enough force it will move"


Dave'H

Dave,

You are right, for most of us it is a hobby, something we enjoy doing and yes "showing off" what we have done.

When (if) I grow up I might make something useful

Dave'H

I'm with the grand kids just watching it go round



Pete