Hello Im New

[Rufe0]

Hi I am Rufe0 or Adam Hill, Male, 24, IT Technician, from England. I have always been into engines and machines in general. Anything that makes or uses power interests me to be honest. However I’ve never particularly had the skills or opportunities to do much DIY stuff. It doesn't help that I am a massive procrastinator but I’m trying to change. I have a ton of ideas for various engines and machines etc. Currently I’m kicking around an idea for infinitely variable cam geometry ( or a system that would be equal to that function ) for 4 stroke IC engines. I have infinitely variable cam timing down solid but this last little bit is going to take some pondering. Also have an idea about a sterling cycle jet engine. This one should be pretty easy to make and relatively cheap, not sure how brilliant an idea it is though. I now work for a company that has some lathes and mills so I could start doing some of these things I’ve been conceptualising. At the moment I’m looking for a good test bed engine to start tinkering on the variable cam idea. I ultimately see it in a small 4cylinder motorbike but that’s a way off. I think I’m best sticking to a simple single cylinder for now. I want something cheap, self contained, simple if possible and preferably not completely tiny. Something like an RC airplane engine wouldn’t be suitable, I want something a lot closer to the 4cylinder motorbike engine. Any ideas? I’m very willing to share my ideas and collaborate with people in anyway I can. Thanks Rufe0

 

[AussieJimG]

Welcome Adam, I foresee some interesting builds coming our way.

Jim

 

[Rufe0]

Hi I wonder if anyone could help me out with something. For this variable valve idea I need a shaft with a thread on it. The tread is a thread pitch something like 1 in 1.8meters, so very uncommon lol. The only way I can think of to make it would be to setup a drill in a lathe and mill it out that way. We do have a mill at work but not with the required A axis. That would be the best way todo it but we just dont have that ability. So I'm wondering whats going to get me better results / easiest, some kind of jerry rigged drill in a lathe or a jerry rigged A axis in a mill? Thanks Adam

 

[Rufe0]

Also how would I go about making the corrisponding nut for this thread?

 

[AussieJimG]

I don't understand your description of the thread pitch. Is this the projected view of the helix? What would be the distance between crests of the thread? What diameter shaft? What sort of thread shape - metric, square, acme etc?

Let's get the thread sorted and then think about the nut.

Jim

 

[Rufe0]

OK, so 1 revolution, or crest to crest would be 1800mm in length. The diameter needs to be probably, well, 10mm dia should be more than strong enough but it could be bigger.

I need a 10mm movement of the nut to equate to a 20degree rotation of the shaft. So its more of a slightly helixed splined shaft than a threaded rod.

 

[Herbiev]

Way too advanced for me but welcome to HMEM

 

[keith5700]

Hi, do you mean 180mm rather than 1800mm?

 

[Rufe0]

Ah yes you are right. 360/20=18*10mm=180mm. So 1 revolution in 180mm. Still probably too much for a our lathes, not sure i've emailed the shop guy but I suspect he will say no.

 

[harrzack]

Ah yes you are right. 360/20=18*10mm=180mm. So 1 revolution in 180mm. Still probably too much for a our lathes, not sure i've emailed the shop guy but I suspect he will say no.

I think this can be set up on a CNC lathe. Cutting threads is just a matter of having the cutter traverse the workpiece at some rate ( pitch).
Gear driven lead screws are limited by the ratios available in the change gears. When the LS is driven by a computer controlled stepper motor, any pitch should be doable.

 

[AussieJimG]

Ok, now I understand. Harrzack is right, it can be done on a CNC machine but I wonder if there is a low tech way (if you need a low tech way). How would Whitworth and Co have done it?

You could cut a piece of paper to the required angle - 180mm in 10*pi mm and wrap it around the shaft. Use it to draw the helix on the shaft. Now running the lathe very slowly, you could manually follow the helix. Maybe take a couple of practice goes but that's life.

You haven't mentioned the thread form. You might need to grind a form tool or two.

The nut can be done using the same trick but you need to offset the guide helix and use a pointer on the carriage.

Jim

 

[Rufe0]

Ha yeah I think it will have to be a low tech solution lol. I can do CNC, even fixed up a machine at work but they are cheap and won't buy a new stepper motor for it lol, so thats not an option at the moment.

I think I should be able to set something like this up. https://www.youtube.com/watch?v=farbfasP7iE although the twist is 1 in 180mm I only need a short section on the shaft so this should work.