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Author Topic: Webster IC Engine build log.  (Read 244256 times)

Offline dbvandy

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Re: Webster IC Engine build log.
« Reply #300 on: May 13, 2011, 09:37:52 AM »
Chris, are you on skype??

I am douglas.vanderbilt... look me up...
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Offline raynerd

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Re: Webster IC Engine build log.
« Reply #301 on: May 13, 2011, 10:48:18 AM »
Hi Doug, I`m not, but I`ve always fancied giving it ago, infact I did a year or so ago so I`ll reinstall over the weekend and look you up.

Chris
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Offline srm_92000

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Re: Webster IC Engine build log.
« Reply #302 on: May 13, 2011, 12:30:22 PM »
Hi Chris,
Did you read Dougs response? maybe not worth spending too much time making a butterfly valve then.

Thanks for that info Doug, Love the Otto by the way :beer: .
I'd decided to get mine running first anyway then I can play :D.

Steve.
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Offline raynerd

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Re: Webster IC Engine build log.
« Reply #303 on: May 15, 2011, 12:39:14 PM »
Hi Guys, yes, sorry missed your last post Steve, yes I have seen Dougs post and will need to think of something because I can`t control mine at all!

Clearly the money I spent at Harrogate yesterday was well worth it as only having the new equipment present in my workshop I managed to get my engine con rod built and back together again. I did say I was going to strip it for final polish and assembly but when I`d built the con rod, I just couldn`t help giving it another way.

So don`t get me wrong, I`m well chuffed, it runs, I`ve built an IC engine  :ddb: :ddb: :ddb: :ddb:

But I don`t have any control at all over the throttle. There seems to be no "give" in the air intake position, too lean or too strong and the engine is just killed. I have had it running for many many minutes now but I`ve taken these photos to show you my problem. They are not necessarly the best examples of smooth running, just that it is working but I can`t control it.

Like I said, if I play with the air regulator on the vapour carb it just cuts it dead, the only slight control I have is if I put my finger slightly over the air intake into the vapour carb. Even then the control is so tricky that I often end up killing the engine as shown in both clips.  The engine will run for several minutes until it is too hot and I knock it off but I can`t control throttle at all.



I should stop moaning - it is running!!  :drool:  :ddb: :ddb: :ddb: :ddb:

I think I`m going to get rid of the bearings in the main frame, they are light duty and I`ve already smashed 2 so I`ll just bush the holes. I`ve sprayed some WD40 on the valve blocks to look for leaks and there is some fizzing from the screws so I need some gasket compound here. Also, as suggested I have put a piece of tubing on the vapour carb to make it act like a bubble vapour carb. I think maybe all this splashing is causing the mix to be too strong and inconcistent, maybe it is worth taking this off.  I also got a nice piece of alluminium for a new base at Harrogate yesterday so I think the plan might be to strip down now it is at least running and have a better troubleshoot to get it running just right when it is in a state more ready to display.

So anyway, proof is in the video, I have a runner :D   They only cut out because I`m trying to slow them down and cut the air intake.

Thanks for the help of everyone and I really mean that. I wouldn`t of stood ANY chance of building this and getting it running without Madmodder.

Chris
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Offline spuddevans

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Re: Webster IC Engine build log.
« Reply #304 on: May 15, 2011, 04:38:09 PM »
Well done Chris, we never doubted you'd get it going  :headbang: :clap: :headbang: :clap: :headbang:


Tim
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Offline dbvandy

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Re: Webster IC Engine build log.
« Reply #305 on: May 16, 2011, 12:54:21 AM »
Well done!!!

With my webster if I plug the intake hole the motor dies instantly, but with the Otto it runs on for another 10 seconds before choking out.  I don't really know why this is as of yet.

In working with Jan, it seems that the theory is that a mixture of 14 to 1 is best and the vapor carb gives this out a bit on the rich side so the air bypass allows you to adjust this mixture to exactly 14 to 1.  I love how the fuel is bouncing around now, that is what it should look like.  Taking off the tube will reduce this, but should make the fumes more consistent. 

From the video it looks like it is turning about 2000 RPM and that should be commended.  Try fiddling with the timing in 2-3 degree increments to see if throttle response improves.  Also, the hole in the bypass might not be big enough to lean out the mixture and with the Aspen fuel it might need a ton of air (just a thought)...

Again, very well done! Now you can study it and fine tune it until it is exactly like you want it.  Maybe you can make the carb in the drawings????? I never did and even the designer says that he had problems with it, but maybe you can be the one to perfect it!

And also, 3-in-one oil works really well is dripped into the intake valve to lubricate the cylinder (that is what I don on the Otto...)


Doug  :coffee:
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Offline saw

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Re: Webster IC Engine build log.
« Reply #306 on: May 16, 2011, 05:30:50 AM »
Nice work congratulations  :clap: :clap: :thumbup:
« Last Edit: May 16, 2011, 02:25:55 PM by saw »
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Offline NickG

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Re: Webster IC Engine build log.
« Reply #307 on: May 16, 2011, 01:26:00 PM »
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

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Offline doubleboost

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Re: Webster IC Engine build log.
« Reply #308 on: May 16, 2011, 04:37:47 PM »
Very nice :bow: :bow:
A credit to your determination  :thumbup: :thumbup:
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Offline metalmad

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Re: Webster IC Engine build log.
« Reply #309 on: May 16, 2011, 08:05:22 PM »
nice one mate :clap:
Pete
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Offline dbvandy

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Re: Webster IC Engine build log.
« Reply #310 on: May 16, 2011, 09:00:14 PM »
Quote from: NickG on May 16, 2011, 01:26:00 PM
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



Here's the problem...  in a "normal" carburetor you have at least two jets, a low speed and a high speed to control the mixture.  IF you restrict the airflow with the vapor carb, you would also have to adjust the mixture to enrichen it due to the lack of air volume through the tank which is needed to produce the vapors.  Once the engine is tuned and running correctly and he has his carburetor sorted, the mixture valve will control the revs very precisely.

I had planned to put a throttle screw in the Otto carb, but found out I did not need it after I got it running on it.

Doug

 
« Last Edit: May 17, 2011, 09:05:34 AM by dbvandy »
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Offline NickG

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Re: Webster IC Engine build log.
« Reply #311 on: May 17, 2011, 04:16:56 AM »
Ah right, I understand. I wasn't aware that model carbs had two jets. The only real experience I have of carbs is SU type where opening the throttle richens the mixture at the same time by moving the needle down on a cam (quite complex at small scale?) Guess the other thing a proper engine does is advance the ignition too so there are quite a few compromises in model engine designs.

NIck
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Offline dbvandy

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Re: Webster IC Engine build log.
« Reply #312 on: May 17, 2011, 09:30:34 AM »
What the little model carbs (and most of the ones you make from plans) have is a needle valve that goes down into the orifice (jet) as the throttle is closed to adjust the mixture.  We are at the mercy of fluid dynamics with the vapor carb and that, in part, is what makes it so forgiving.  

With a normal carb you change the size of the jets to change the mixture, smaller hole ==> less fuel ==> leaner mixture.  In the OS2a carb (and all of the others) there is a needle that in essence "plugs" the hole that the fuel is coming through as the barrel throttle valve is closed.
 

This adjustment is what gives us so much hassle because those carbs are designed to run on nitro methanol (alcohol) which requires more liquid and thus the jets are larger.  So, when we put gas through them, there is too much and they either run rich at idle or rich at WOT, there is no in between.

I tried for two weeks or more to get one of the two RC carbs to work with either motor reliably, but never could on either motor.  When I discovered Jans vapor carb online, studied how it worked and made my own, it was a glorious day.  This is what mine looks like:



The mixture screw on the top is the high end and meters the maximum amount of fuel that will come through the carb and the screw on the side meters the fuel at idle by plugging the hole that the fuel is pulled through.





There is a really good writeup on the workings of the RC carb here: http://www.oocities.org/ericperez_2000/Carb_101.html

Worth a look.

Doug
« Last Edit: May 22, 2011, 09:44:13 PM by dbvandy »
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lordedmond

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Re: Webster IC Engine build log.
« Reply #313 on: May 17, 2011, 10:25:42 AM »
the ones I used in the past were very simple ( although theses were for 95 nitro with a dash on methanol and a smidgin of castor oil )


they had a flat throttle slide with two needle jets one above and one below the flat slide , the one below was flush with the side wall of the venturi , the one above had a beak one it at 45 degrees facing downwards that was the main jet the other was the low speed jet.


the throttle slide had just a plane hole in it


you could at that time buy from the model shops replacement needle valves complete its those that I used




so the order of things from the air in  was jet with a 45 beak looking down ,throttle slide, and a jet flush with the side wall

to set up I used to close off the bottom jet open the slide and adjust the main mixture, then slowly close down the slide and open up the lower jet to get it to idle


Theory  is that the top jet with a beak would tend to richen up with increased air flow wears the bottom one would weaken


Stuart


dbvandy Doug check your email
« Last Edit: May 17, 2011, 10:38:38 AM by lordedmond »
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Offline raynerd

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Re: Webster IC Engine build log.
« Reply #314 on: May 22, 2011, 05:30:40 PM »
Guys, I`m really sorry, I didn`t read these last two replies until today. I just missed them totally!! Sorry. Lots of good info. The info really helped in my understanding of how a carb works

I`ve still not had time to test anything on mine as it is currently in bits ready to be put back together on a new base. I`ve made a couple of changes. I`ve profiled the fly wheel a bit which I think looks a bit better. I`m considering painting the flywheel...I can`t make my mind up. I`ve also replaced the brass inner section of the fly wheel with a steel one, threaded it M4 and drilled right through into the crank shaft so that it won`t slip at all and is nice and solid. Not the best photo, looks quite good in person but..



paint or not?

I also had an issue with the timing of the ignition. Although it was easy enough to undo the grub screw on the magnet holder, I realised I needed a way of adjusting it whilest running. To do that I had to get rid of the base mounted sensor holder and make a bracket for the sensor that could be swung around the axis of the crank shaft. I`m sure there are many neater ways but I`ve not used my rotary table in a while so I went for this option. Basically I bushed the hole in the side frame that the crank goes through and purposely left 2mm sticking through the front side. I then turned down a large diameter of ally, drilled it 12mm the OD of the bush and then reamed it so that there was a recess in which the magnet holding disk could sit. I then mounted it on an arbour:



I then took down the thickness of the back side and milled a V in the top, this was so I could get an allan key in to tighten up the magnet holder in an approximately correct position. An arc slot was then milled through the side and a M4 hole cut into the side frame. The sensor will be fed up into the support from the bottom, the support and sensor can then be rotated (on the bush OD) during running to get the best setting. This is just a dry pose you can hopefully see the idea.


I`ve cut the new base to size, I just need to mark out. I`ve got a little more polishing and then I`m ready to put it back together again!





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Offline saw

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Re: Webster IC Engine build log.
« Reply #315 on: May 22, 2011, 05:43:12 PM »
Looking good, nice work. I'll hope that your'e problems is gone  :D
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Offline dbvandy

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Re: Webster IC Engine build log.
« Reply #316 on: May 22, 2011, 10:23:32 PM »
Good job on the design of the adjustable ignition.  This is when this gets fun...  you can stare at the engine and get mental pictures of how you can make it better and your own.

By the carbon on the piston, we can tell it is running well....  now we look forward to a fancy video it it running at your command.

Doug  :coffee:
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Offline raynerd

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Re: Webster IC Engine build log.
« Reply #317 on: June 06, 2011, 03:55:46 PM »
All this polishing and making new better parts has taken a lot longer than I expected. I had it running quite well a few weeks ago and I must admit since disassembling it and rebuilding into a polished "finished" state I`m struggling getting it running nicely but here it is on its new metal base and new wooden base that my brother in law made me. The base is hollowed out so that the electronics can sit under it. I made a little split grommit which grips the spark plug cable and I think it has turned out really great dropping down into the base plate. The adjustable ignition sensor looks nice and will hopefully work well when I get the intake working OK again. I don`t know where I`m going to put the fuel tank yet which is why it is still not in the photo. It fits at the front and at the end. It was originally to go at the end which is why there is space there. Next question is how to secure the tank down. Anyway, a quick photo to show the progress....   I must admit, I`m ready to get this finished soon and move on, I feel like I`m going around in circles



Hopefully a video soon to follow!
« Last Edit: June 06, 2011, 03:57:56 PM by craynerd »
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Offline NickG

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Re: Webster IC Engine build log.
« Reply #318 on: June 06, 2011, 05:51:40 PM »
Looks fantastic Chris, the finishing touches have made it look really neat and tidy. Wooden base is impressive too, how did you do that?

Nick
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Offline raynerd

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Re: Webster IC Engine build log.
« Reply #319 on: June 06, 2011, 11:24:19 PM »
Quote from: craynerd on June 06, 2011, 03:55:46 PM
.... and new wooden base that my brother in law made me.

Yes, I can`t take any credit for the wooden base. Thanks for the comment Nick, glad you think it looks neat and tidy that is what I was aiming for.

Chris
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Offline metalmad

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Re: Webster IC Engine build log.
« Reply #320 on: June 07, 2011, 02:17:50 AM »
Very nice sense of style about this engine now
well done mate
Pete
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Offline raynerd

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Re: Webster IC Engine build log.
« Reply #321 on: June 07, 2011, 06:51:09 AM »
Thanks for the post metalmad! I`m glad you think it is looking nice. I`ve put more effort into the detail and final display appearence of this engine than I have into any of the other engines I`ve made.

Grrrrr - I`m still getting this inconcistency! It ran for a good 3-5 minutes until I choose to stop it, let it cool down and started it up 10 minutes later and  ran it again, it kicked up fine and ran again until I stopped it. I went to work and just got back now, I`ve not changed a thing and it won`t start!! It is firing and trying to tick over but it just won`t run! I`m going to lie shortly and tell you all it is running just fine because it is driving me insane and I want to start a new project!!!

Chris
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Offline spuddevans

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Re: Webster IC Engine build log.
« Reply #322 on: June 07, 2011, 06:55:11 AM »
Looking really good now Chris. It really looks the business now on the base.

I'm sure you will get the inconsistancies ironed out, just keep plugging away at it.


Tim
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Offline raynerd

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Re: Webster IC Engine build log.
« Reply #323 on: June 07, 2011, 07:28:21 AM »
Cheers Tim - it running smooth as anything now, now problems at all  :lol: :doh:  :palm:
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Offline arnoldb

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Re: Webster IC Engine build log.
« Reply #324 on: June 07, 2011, 08:14:16 AM »
Looks great Chris  :thumbup:  :clap: :clap:

The hardest part of building an engine is always the last bit when putting a final finish to the parts - that's why I've switched to trying to finish all the parts as well as I can while making them.   Overall a build then lasts a bit longer before one gets to see it run, but it's a quick job to do the final finish and assembly  :thumbup: 

Regards, Arnold
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