Cylinder Bore 7/8" at a depth of 2.5" OR use DOM/CRS ?

[Jasonb]

Thats provided your roughed out bore is true to the outside of the liner!! You also need to ensure that your clamping pressure doe snot distort the liner, I assume its about 1/16" wall thickness

I'll mock up the way I did the liner on the engine in my avitar and take a few pics, that wa sdone with a between cts bar


J

[John Stevenson]

Thats provided your roughed out bore is true to the outside of the liner!!

J

Sorry, missed that, I thought it was a cast cylinder, in which case make part of the bore taper out to the OD and register on the OD of the liner, then pack up and clamp.

Using the tapered bushes is standard operation on line boring machines and adjustable reamers with extension pieces on for line reaming.

John S.

[Dean W]

Chris, you got another batch of good ideas for setting up to align bore that cylinder.  I don't have anything
new to add.  I hope you'll show us your progress!

[Jasonb]

Here is the mock up of how I did the liner for the engine in my avitar.

First machine the liner OD and rough out the bore a littel undersize, you can come at it from both ends if your normal bars are not long enough.

Next take a block of wood or laminate up some MDF and bolt this firmly to your cross slide, the top of the wood needs to be on centre height or a fraction below so you may need to pack & shim it up. This block was used on a smaller lathe but I had two bolts in each slot.



Next screw a second block to the first, mark it so it goes back on the same way and put a bit of card between the two blocks.




Now bore a hole through the two blocks of wood, first with progressively larger drill bits in held in the 3 jaw and then switch to your between cts boring bar until you have a snug fit on the OD of the liner.



Its now just a case of loosening the top screws, removing the card and place the liner in the hole, screw back down and the liner will be held concentric to the lathes axis for boring with the between cts bar. DO NOT disturnb the bottom block.

J

[raynerd]

What a fantastic idea - thanks a lot for the suggestion! I`ve no T-slots on my saddle so I`d have to come up with some way of bolting the wooden block down but that really is an excellent idea. So by boring the wooden block you are ensuring your cylinder will be held aligned!

Sorry if this is a stupid question but a few of you have mentioned "liners". As far as I can read into the plans, the cylinder doesn`t have a liner but is just bored straight out of a bar of cast iron. I presume it is exactly the same idea, I just wanted to clarify considering liners have been mentioned a few times.

Chris

[Dean W]

Chris, being your cylinder is made of CI, you don't likely need a liner.  Those are usually used when the outer part of the cylinder
would be made of something like aluminum.  A good material for dispersing heat, but not for a cylinder bore, so a liner would be
pressed in to get the best of both worlds.

Jason, nice demo you put up!

[Jasonb]

Yes, I was forgetting yours is an aircooled engine, just bore the wood to fit the OD of the cylinder.

Liners are often used on water cooled model engines as the cylinder has a hollowed out section for the water to flow through and the liner closes this off, it would likely have been cast in on a full size.

Jason

[raynerd]

Excellent...thanks, I thought it was the case but it was worth checking!

I`m sorry to be a pita, but I do have another questions. I`m just wondering how to ensure that the bore of the cylinder is square to the face so that it aligns properly and the piston does not try and enter at an angle. I presume to ensure that it is square to the bore, facing the cylinder should be ideally be done immediately after or before boring while held in the same position in the wooden block. If this is the case, I can only imagine you can face the front end while held in the wooden block, by flycutting in the lathe?? That would ensure one face (which would be the front) is square to the bore. Am I right with regards to this or is there are better method?

I will have to cut the fins on the cylinder as well, perhaps a good fitting tapered stub or expanding mandrel into the bore and face up both ends from this and also cut the fins at the same time would be another method?

Chris

[Jasonb]

You can machien one end and the OD at the same setting in the lathe chuck. Then bore in your wooden block with teh other untrue end facing teh headstock so you can as you say flycut the end, I would make this end the crank end.

A mandrel would also work, expanding would liekly be best on this size engine and may well hold better against the parting cuts for the fins.

You could always do the fins while the bar is still in the chuck and use a tailstock centre for support, Think I would go this way as you will get the best grip of the work.

Jason

[raynerd]

Jason, sorry, must have missed your reply. Thanks.

When you say, "You could always do the fins while the bar is still in the chuck and use a tailstock centre for support," do you mean when I am taking the cast down to size in the chuck before boring, cut the fins at this stage? I did consider this but was worried that removing material off the outer diameter for the fins would leave less surface area for the wooden block to clamp down on ready for boring.

[Jasonb]

Yes do it before boring so the ctr will go into a ctr drilled hole. Don't think grip will be an issue particularly with hardwood or MDF

J

[NickG]

Chris, have you started your Webster build yet? I missed the fact you were even making one until now. I've often pondered making one. Can't wait to see your build log.

NIck

[raynerd]

Hi Nick, thanks for posting and the interest. Yes, I have started in a way. I`ve got all my materials together including cast iron for the cylinder and also aluminium plate for the base and supports. I`ve got the little spark plug, I just need a M10 x 1 tap! I`ve also got all the details for the gears and spent hours planning and calculating cutting these as I`m making them myself. I`ve roughed out all my materials for the two supports. So I have kind of made a start but nothing to shout home about. When I start boring the cylinder I`ll start a project log. Problem is I opened this thread and got    into boring between centers so I`ve spent the last week making that "Device for setting up for boring" that I posted in Project logs, that is for the cylinder and I`ve also since realised that because my lathe saddle doesn`t have T-slots, I`ve started building like a tool plate that will fasten to the saddle in place of the tool slide so that I can clamp my cylinder down...again for boring between centers. So basically I`ve been making tooling to allow me to start. I`m slow as hell when it comes to machining and I only get a couple of hours every other night if I`m lucky...

You should join me in making one for yourself.... !

[NickG]

I might have a tap you could borrow, not sure if it's 1mm pitch, will check. It's probably better to bore between centres, sure it could be done without though. I get about the same shop time, on a bit of a roll the last few nights but  that's rare!

I am definitely going to do an i.c. soon, I just need to get the 2 poppin's done, the 7 1/4" electric loco and I'd like to re-try the little stirling. So I'm not ready yet, otherwise I'll have loads of started projects and it winds me up a bit thinking about them all!

Things like the gears for instance I wouldn't be able to make so I'd have to find some that were suitable or go for a 2 stroke for my first i.c. maybe.

Nick

[raynerd]

Nick, if my gears work, I`d be sure to save the cutter profiles and it should be easy enough with my cnc rotab to make a few more.... 

[NickG]

Chris,

I remember the Webster being the first i.c. engine I could find plans for on the internet and it had a good build log with it. However, since then I've seen others that I'd like to have a go at. I really set my heart on a hit & miss but some of the linkages appear quite complex / fiddley and difficult to get to work authentically on very small engines so might give that a miss until later in life! I don't know whether you've seen it but I really like Arv's (putputman) Tiny i.c. over on HMEM. A good few people have built it with good results now and it won't cost much material wise.

I think I'll give the Webster another look before I make my decision though as it seems pretty robust and uses stuff like car contact breakers which will help matters. How much was your spark plug if you don't mind me asking? Can you squeeze a normal 14mm car plug in there? I know it wouldn't really look quite right but the webster isn't really designed for aesthetics!

Nick

[raynerd]

Nick, I`ve seen the tiny Ic engine it just looks fiddly but actually my preference is Malcome Stride's - NE15s engine. I want to build that but I just thought it was a bit tricky for a first build. I`ve now got hold of the plans and have read through them and I`m still pleased I`ve gone for the Webster. I`ve only just got my head around how the engine works !! so it`ll be a nice simple first build.

I`m not one for giving advice, I wouldn`t have a clue if you can fit a 14mm car plug - I`m just a lemming, I just follow what others have done! The plans called for a 1/4" x 32tpi plug which are expensive BUT then he changed it later on to a 10mm NGK CM-6 spark plug which most seem to use! It was cheap - £3.50 ish including the postage!
http://cgi.ebay.co.uk/1x-5812-CM-6-CM6-NGK-SPARK-PLUG-/190459015786?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item2c583df26a

I don`t see why a 14mm car plug wouldn`t work but for the price, I`d just go with a CM6.

Ignition is the only thing I`ve not got sorted. I`m also going to put some money into a RC carb as they seem to run much better on these.

Webster looks a  nice build but as John mentioned, I also considered and ask Jan Ridders for his plans for the simple IC engine. That looks nice as well but to be honest I have just seen more running Websters and so I presumed I`d get more advice if I got stuck.

Chris
 

[NickG]

The tiny i.c. looks fiddly but I don't think it actually is when you look at the way each component has been designed. I'll probably have to eat my words at some point for that  Is that the nemmet overhead camshaft one from model engineer? I was buying Model Engineer at the time it was serialised and was very interested in it. It looked simple but not sure it was when I started looking at the components and methods involved! I prefer something that'll be a slow runner as well rather than something buzzing away.

Ah right, that's much cheaper than I expected anyway for the 10mm plug! No point bothering with the 14mm one then! I was thinking of making a glow plug for even more simplicity, less stuff required and the plugs look quite realistic. I've seen people make successful spark plugs but I can't see me managing it - buying a proper plug would eliminate the source of another fault for me!!

I also like the Ridders engines - the simple one seems to be the pressure controlled 2 stroke and his vapour carbs seem to work reliably. Hmm, so much to choose from these days!

Nick

[dbvandy]

Chris,

I have just completed my webster build and I used 7/8 id x 1 od DOM for the sleeve and 1 id x 1.5 od 6061 aluminum for the cooling fins.  I also used 6061 t6 for the piston with a 7/8 viton o-ring.  It has about 10 hours on it and is going strong... I have even had it up to 4000 RPM for 10 minutes at a time, but it gets pretty hot.  Here are some pics to help you out...

Doug