Chris, there is a lot of debate over this subject! I think there might be some info in the tiny i.c threads too. I'd be tempted to go for a lapped bore and cast iron piston with not much clearnace. I know Jan Ridders does that on his engines.Hi Chris, as a matter of fact, boring on a table with the bar between centers is far and away the most accurate way to bore, and misalignment of the bar only affects the roundness of the bore, and does so absolutely equally the full length, and takes lots of misalignment to make a noticable difference. That said, having made a very straight and accurate bore, the idea of lapping and using a very close fitting cast iron piston would seem to be a more accurate way to get where you want to be. The reason for the odd sizes on the grooves for a viton o ring, is to allow compression of the o-ring, while giving plenty of room for it to expand laterally, so the rubber is not compressed, but merely displaced, and causing much less friction. An iron piston in an iron bore expands at the exact same rate for both, and keeps what ever clearance you have consistent, regardless of the temperature, and the graphite nodules in the cast iron make it self lubricating to a very large degree, allowing for very close clearances. :beer: cheers, mad jack
Hi Jack, thanks for your input regarding the piston seals. I`m not happy with the base material and so until I can save up a little cash for an all base (I`ve spent far too much this month to buy ANYTHING), I`ll just keep some bits on hold. Consequently I`ve made a start on the gears. I`ve made the buttons and holder this evening and I`ll take the buttons to work and harden them. Then hopefully in the next few days I`ll cut the cutter and then by weekend should aim at having a start on the first gear. I hope my calculations are correct, I`ve used mainly John Stevensons gear article, I think I`m in control....Hi Chris, I just wanted to remind you, nothing depends on the base, not really, so you can use what you've got at least temporarily, and just leave the base to last, and if what you use in the interim works out, you may find yourself keeping it. These are OUR engines and we can make them look or do what ever we want, no one can tell us what's good or bad, they can go build their own if they don't like it. That's how I tend to look at this, since it is my hobby, and not theirs. Take your time to enjoy the build and take pleasure in finding new ways to do things which people tell you can't be done that way, but spend your time in the shop pleasurably, making the finished product what you want it to be. :beer: cheers :poke: mad jack
(http://www.raynerd.co.uk/wp-content/upLoads/img_0506.jpg)
Nice gear Chris well done.
That tamed the beast :whip:
Stew
dbvandy - yes, I did wonder if it was needed. If you are not using the grub screws how is yours staying in position - friction fit?
Thanks for all the info regarding the piston o-ring. I`ll let you know how I get on.
dbvandy - I`m really not sure what I`m doing about ignition yet. A lot of it falls down to cost, what you showed me seems an excellent price. I`d quite like to use my smaller 10mm spark plug so I`m not sure if it`ll fit in place of the 14mm plug that comes with it. I`ve finally got my head around the points/contacts system that the original plans suggest but they look clunky and I believe I could do without them if I used the item you linked to?
Where or what is the hall sensor in this bundle and how will it be fitted?
(http://www.hobbyking.com/hobbyking/store/catalog/CM-6spcap.jpg)
I believe this is the sort of thing:
REMOVEhttp://www.youtube.com/watch?v=jeRE8SoxStU&feature=mfu_in_order&list=UL
...but it worked out about £90+ when I priced it up. Is it the same sort of thing in the link that you have suggested?
Thanks for all the info regarding the piston o-ring. I`ll let you know how I get on.
dbvandy - I`m really not sure what I`m doing about ignition yet. A lot of it falls down to cost, what you showed me seems an excellent price. I`d quite like to use my smaller 10mm spark plug so I`m not sure if it`ll fit in place of the 14mm plug that comes with it. I`ve finally got my head around the points/contacts system that the original plans suggest but they look clunky and I believe I could do without them if I used the item you linked to?
Where or what is the hall sensor in this bundle and how will it be fitted?
(http://www.hobbyking.com/hobbyking/store/catalog/CM-6spcap.jpg)
I believe this is the sort of thing:
REMOVEhttp://www.youtube.com/watch?v=jeRE8SoxStU&feature=mfu_in_order&list=UL
...but it worked out about £90+ when I priced it up. Is it the same sort of thing in the link that you have suggested?
I`m just looking over this and your right, this really is a bargain as it works out at £20 including postage providing it doesn`t get caught up in customs. I have been stupid and didn`t see that it is fitted with a CM6 plug which is what I wanted to use anyway!! The link you sent John looks excellent and once I`ve got it running it might be something I experiment with for fun so that I can say it is truely all built including ignition but I expect I`ll have enough issues getting it running than worrying about building the ignition system as well. I think I`ll go ahead and order one of these for £20.
This looks like you are coming right down to the last little bits... Question and please forgive my ignorance since I'm not an engine guy... Are the basic differences between the different spark plugs defined by the following three items...? The dielectric resistance, the operating voltage to strike a spark and the sustained current?As a life long engine mech, the primary differences in plugs are thread size, the length of heat path from center electrode to cooling, and the size of the plug its self. Resistor plugs are the common thing because they don't cause radio interferance with modern electronics, so their resistance is pretty common, and the plug size has gotten smaller because engines are so much smaller in weedeater applications, but other than that, plugs are pretty much the same, with the ignition units making most of the difference. Almost any form of ignition will fire across a .020 in gap, and with model engines, this means we can use very small coils and low voltages, if we wish to. I just pulled a champion plug from a weedeater engine which is ten mm thread, the smallest plug I've ever seen, and I believe it is the same as the cm-6, although I haven't seen on of those except in pictures. In general, the higher the number, compared to other plugs of same manufacture, the longer the heat path, and the hotter the plug runs. In an engine which is run continuously and for long periods, this is critical, as a too hot plug can cause a hole in the piston. For model engines, this is not normally even an issue at all, and hot plugs don't foul as easily. If you find your plugs getting fouled from messing around with timing, mixture and oil, the easiest way to "clean" it, so it will reliably fire is to hold it in a vise on the wire end, and aim a torch flame down between the center electrode and the casing with the threads, trying to get the blue tip of the flame on the center electrode. Any oil down deep with show up as a pale blue flame around the opposite side of the ground electrode, as opposed to the reddish spread flame of the torch impinging on the steel, giving it the reddish hue, and aiming between the center electrode and ground from both sides, hits the hardest part to get up to temperature, and once there is no more light of "phantom" blue flame on the opposite side from both sides, you will fine pristine ceramic on the center electrode when it is cooled off. :beer: Cheers, Jack
I also had to made an adapter for the small 24 tooth spur gear so that it could be also held to the crank. The plans call for the spur gear to be attached to the flywheel but I figured I`d have no problems just using grub screws to fasten each to the crank independently.
1. Obviously any advice regarding the soldering of the brass kernal to the cast iron surround would be useful even thought my flwheel is now made.
2. I now have to fit my 48 tooth spur wheel to the frame to mate with the 24 tooth gear. The plans just call for accurate measurement and drilling the frame to mount the stub on which the spur gear will sit. I`m just worried about the accuracy of this method.
I've seen that flywheel someware before :scratch:
Stew
So the next job now which I am absolutely dreading is the valve block - I really need to get my head around this, how it is machined and what the parts are even doing!
Could anyone who has made the webster explain, or ideally a photo, to show how you have made your spring to keep the lever lifted?
THE most important thing with the valves is doing the face and stem in one setup so that they are concentric... same with the guide. Do the guide first and drill out the hole for the stem. then you can measure it with a numbered drill and match the stem to it perfectly. Mine are .007 different (don't know how the heck that happened, same drill, same setup...), but the valve stem was turned to match, so there is .0025 clearance on each.
Doug - I haven`t thought too much about the springs yet. I guess they are quite important in terms of how much pressure they are applying - did you wind your own springs or where did you get them from?
Sorry Doug - it says that the adapter is loctited to the carb, but what about the other end into the valve block - loctite here as well? I just thought a thread on this end would be better??
Doug
Thanks for then info!! You have ben very helpful!! I`m sorry, I have been meaning to say that I have been intending to use the vapour carb for months now so yes, I will be taking your advice here. I just keep talking about the "carb" because it is what the plans state. OK, thanks again.
I`m struggling like hell to cut the valves. Must have wasted about 5 hours now on unsuccessful attempts. 1" is just causing chatter and a terrible unusable finish on the shaft.
Chris,
If you still have trouble making them from solid, the other way is to silver solder the valve head onto a precision shaft, and machine it to shape afterwards.
Just another recognised way to do it.
Bogs
The plans on page 10 state that the valve guides are "pressed and loctited into place" in the valve block. I was presuming that the valves would therefore be at a very similar temperature as the loctite supporting the guides in the blocks.
Guys, I did reply to these messages but my battery went on the laptop and I lost it, then I lost the will to repeat it! Sorry. Basically I was appreciating that I was being a moron considering loctite!
Finally, I have made a successful valve after many failed attempts at one piece valves. My pal Rodger kindly offered to silver solder some .25" heads onto 3/32" drill rod shafts with me, so that the valves could be machined from these blanks. I haven`t done any silver soldering so although I did consider this method, I couldn`t attempt it. Once I had these blanks at home, it took me 10 minutes to complete the valve, including cross drilling the 3/32" shaft 1mm, which surprisingly went just fine!
I`ll show pictures of the valves once complete and polished, but here is a quick photo of the first valve I made with the 3 other blanks behind it (I only need 2 valves, so we made 2 spares!!)
(http://www.raynerd.co.uk/wp-content/upLoads/1valve2.jpg)
Nick, you made your post while I was posting an update. Yes, it is a good point! I`m not too sure how or if you would put a viewing window in a vertical tank, also the air inlet stream needs to blow down on the fuel to create the vapour. Jans first design was the bubble carb, where the fuel actually bubbled through the fuel. This seems like a really great way to vapourise the fuel so I`m not too sure why he changed it. With this new version, the tank is only filled about half full and the pipe intentially does not go below the fuel level. It is an interesting concept the vapour carb, I just hope it works for me :D
Doug, interesting post you made! Have you got any advice regarding the timing? I`ve been reading over the build notes and I`m trying to make sense of it!
Chris
I keep dreaming of that noise :dremel: thanks for your replies stew and mad jack
My thrust bearing arrived today. I admit I've never seen one before. There seems to be no way of clamping it to the shaft so I did some googling. Am I right in thinking that it isn't clamped to the shaft but actually tightens on the shaft when the locking mechanism kicks in. This would then link to your comment, Doug, of the shaft needing to be hardened. I purchased my one way bearing from a model shop and it has no dimensions on it. I'll experiment tonight but can anyone tell me, do I just turn the shaft diameter so the bearing just slides on? If this is the case I can imagine tolerances would be high or the bearing will slip?
Silver solder arrived, got a rollocking of the wife for soldering on the cooker top. But the job went very well!
Another hour spent on it, a good few pops but never at all feeling like it's going to go. :( soon to be free to a good home :palm:
I`ve just gone down now again before bed (wife is saying I`m obsessed)
QuoteI`ve just gone down now again before bed (wife is saying I`m obsessed)
Yes I get that, don't know why :scratch:,
Perhaps they'd understand if they had a shed.
Chris you say you can hear the spark ,is it in the right place inside the cylinder or is if outside , i.e. plug cap shorting
I would, although I may be wrong but I would have though you would not be able to here the spark if its the plug firing in the cylinder
a short note but I will leave it to Doug but a timing light will tell you when to plug is firing , but its it is not the plug that is firing but a stray spark it will sill tell you its firing
Stuart
question... did you assemble the plug boot with the little wire spring that goes around the tip of the spark plug?
Chris you say you can hear the spark ,is it in the right place inside the cylinder or is if outside , i.e. plug cap shorting
What was your piston made from again? If it's aluminium and it's too close, it could be binding in the cylinder. It expands a lot faster than cast iron.
The abrupt stop suggests tp me a tightening up probably as a result of piston expansion due to ignition temperatures.
Try some real gas... way more aromatic, so should provide more bang...
2. try some gas (petrol 87)
I did remove the check valve some time ago based on one of your earlier post. There is no ball bearing in there so although you see the "check valve" case, there actually is not valve action, it is just a way of attaching the tube to the valve block.
Petrol 87 ?? "Real Gas" ?? Are we talking about unleaded petrol here? I`m sorry, just don`t want to explode anything attempting to run it on what I would consider "gas" ...methane!
I'm just starting a Webster build, made the first chips yesterday. I was planning on putting a butterfly valve of some sort between the vapour mixture control and inlet so that the mixture can be left right but the flow controlled, maybe something like that would help yours.
(And it'd help me if it works.... or doesn't )
Steve.
Nice 1 Chris, I will be extremely chuffed if my first i.c. turns out as good as that. :thumbup:
I think it might be worth a try with the butterfly valve still, am sure I've seen one working somewhere. I see what doug is saying about the vacuum, but then again, it's still pulling the same air through per revolution so it should still work I reckon.
It doesn't have to be as complex to make as a butterfly either. It could be something like the attached diagram.
Nick
.... and new wooden base that my brother in law made me.
. ignition not made by a 12 year old Chinese girl...
. ignition not made by a 12 year old Chinese girl...
Didn't realise you two had met!
I've not reverted back so the inlet is just blowing over the top of the fuel and disturbing it rather than bubbling through it.
Chris
Following on from the last pictures ...
I turned the OD of fuel tank / vapour carb down to make a nice looking brass cup :D
(http://raynerd.co.uk/wp-content/upLoads/janvap1.jpg)
The top air intake is two piece. An M10 tapped insert soldered into place to allow filling of the tank and then a screwed insert for the air intake reducing the air intake to an 3mm hole tube. The shoulder of the insert is contoured on the shoulder to allow it to sit nicely on the tank. I couldn`t for the life of me think how to do this and so a friend and fellow madmodder suggested a two piece design, where a washer is used as part of the shoulder and the washer filed and sanded to shape. This worked really well but I would be interested to know how this could be made from 1 piece as per the plans
(http://raynerd.co.uk/wp-content/upLoads/janvap2.jpg)
The fuel/vapour outlet tube was then made...not the best photo but all the parts here are ready for soldering..
(http://raynerd.co.uk/wp-content/upLoads/janvap3.jpg)
My sophisticated soldering setup...the cooker top.
(http://raynerd.co.uk/wp-content/upLoads/janvap4.jpg)
And then all polished up... I`m really pleased with it! I just need to make the main air intake insert and the nut which covers the additional air intake on the threaded outlet, glue on the glass viewing window and put it on a stand and then I`m done. Getting there...!
(http://raynerd.co.uk/wp-content/upLoads/janvap5.jpg)
I believe I`ll need a one way valve as a must as well, so they will be the next things to make.