Scale model Economy hit & miss engine builders wanted

[Charles 2010Participant @charles2010]

More photos on forum

 

Here is the engine ready for testing

[Charles 2010Participant @charles2010]

I have now made a starting handle with atuto disengage …

 

I hope it will help the starting of the engine …

 

 

I will remember to keep my thumb out of the way !!!

[Charles 2010Participant @charles2010]

24th November 2010

The day that my Economy model engine ran properly for the first time …

 

I have redesgined the carb and made it to my own drawing below .

You can see more picture in the album.

The most important points I think are:-

 that there is a great deal more air flow around the needle,

that the fuel entry is at the base of the carb

 

So I agree with the other poster that the carb as designed with the engine could well be over engineered.

 

There is still much to sort out as the hit and miss does not engage so likely to be a spring problem as mentioned by another poster.

 

Regards Charles

 

[Charles 2010Participant @charles2010]

Well here it is running

The smoke soon cleared when the excess oil had burned off – honestly

 

 

The lower hand ( of a friend ) is steadying the ignition box and the upper hand (mine)just steadying the engine  which made the “workmate” rock about a bit too much !!!!

Regards Charles

[ronnie barkerParticipant @ronniebarker18785]

charles

im glad you got your engine to run, once you got it set up and bolted down the engine should run nicely being of a good size.

 

i would think the hit and miss problem is just govenor spring which should be easy to sort.

also check the inlet spring as if this is to week it will suck to much fuel in and fire more 

 

best wishes jonathan

 

[Charles 2010Participant @charles2010]

Thanks for the tips Jonathan.

 

I am also going to strip it down completely and have a good look at all the patrs and probably paint it during the re-assembly.

 

It is great to have made a 1910 engine  but I still can experiment with ignition and there are a few other parts to make better …  such the crank shaft as the key way is not cut well and allow the flywheel to knock against the keys ….

 

All a great learing process …

 

Regards Charles

[Sub MandrelParticipant @submandrel]

Well done Charles,

 

it looks like you are running it at 7,000 rpm…

 

Neil

[John OlsenParticipant @johnolsen79199]

You should be able to make a stepped key if the keyway in the crankshaft is wider than the one(s) in the flywheels. Seems easier than making another crankshaft anyway.

 

regards

John

[Charles 2010Participant @charles2010]

No that sounds a brillient idea about a stepped key way to stop the knocking sound that I get from. the flywheels.

 

I will look into doing that tomorrow even if I need to mill the key way in the crank to clean it up. I must have rushed the job or not taken enough care!!!! 

 

Also however when the crank came apart, a little, it has not gone back exactly aligned so the new crank shaft may be still in order eventually and I may try to turn that from a solid lump. Now there is a challenge.

 

I drew up the cad diagram tonight and found I will need  piece of stock 3″ diamter to allow for the size of 5mm between end of crank and the big end and similarly the other end. BUT may be as I am cutting this from solid I could say 2mm each side and then I couldjust about get it out of 2 1/2″  stock.

 

I am building a rev counter  / tacko so I soulh be able to say for certain at what speed  the shaft is turning !!!

 

Regards Charles

[John OlsenParticipant @johnolsen79199]

Have you thought of making the new crankshaft from a piece of flat bar? This can be either a piece of flat plate flame cut to shape or a piece of ordinary bar stock, eg maybe something like two to  three inches wide by 1 and a bit thick. Most big suppliers of steel plate would be able to flame cut the blank for you, leving of course a good machining allowance. Actually these days they might plasma cut it. But either way that gives you a blank that is close to the  required shape and saves a lot of machining and swarf. If you can’t get it done that way, then a lot of chain drilling and a bandsaw is another approach to get the bulk of the material off. Incidently neither the flame cutting nor the plasma should leave anything that is hard to turn away.

 

Another approach is to make a pattern and have it cast in SG iron. I made a two throw crank for my steam launch engine like that, three inch stroke.

 

Then once you have a suitable blank, think about the possibility of milling most of the rest of the material away. For this you need a mill (of course) and some way of holding the job between centres. I use a Vertex dividing head and tailstock, but it does not need to be that sophisticated. Using a big end mill you can mill the shape down to within ten thou or so of nominal size, then take the rest off between centres in the lathe.

 

The big steam launch crank was milled almost to size, then ground in an automotive crank grinding machine. The only turning on it was done on the Myford ML7, so you can imagine the looks I get when people ask how did I turn the crank! It just fits between centres, and the balance weights have to be clear of the saddle, but it will go in there…but not offset for turning big ends of course. There are some pictures of that with an article I did for ME about making cranks a few years back.

 

Incidently the old timers used to make some very tricky keys. One idea was an offset key, used to adjust the position of a steam engine eccentric when you managed to get the keyways slightly wrong.

 

regards

John

 

 

[MichaelRParticipant @michaelr]

As John says use flat bar for your solid crankshaft I did this for the crankshaft on my RLE hit and miss engine, if your crankshaft has balanced webs you could make those as separete items slotted and fixed over the plain webs, these could be made from flat plate or a couple of slices of suitable dia round bar.

[Charles 2010Participant @charles2010]

 

Thanks for all the ideas on a new crank shaft and the pictures are a grat inspiration.

 

Can anyone tell me the correct sort of RPM at which I should aim to operate the engine?  450 tp 1000 RPM ???

 

Regards Charles

[Ian S CParticipant @iansc]

400-500rpm would be good, I supose a small motor might want to run faster.

Just finished a crankshaft out of a bit of scrap, its a bit smaller, 8mm main shaft, its for another hot air engine, second one this month.Ian S C

[MichaelRParticipant @michaelr]

Edited By Stick on 26/11/2010 15:45:07

Edited By Stick on 26/11/2010 15:47:05

[MichaelRParticipant @michaelr]

Messed up my other post, a video of a Economy running.

http://www.youtube.com/watch?v=q9kGnU5cXXY

 

Hope I have got it right this time, and the link works.

[Charles 2010Participant @charles2010]

Thank you for pointing me in the direction of the video and he also confirmed about  500rpm is about right for slow running.

 

I also like the external fuel tank !!!!

 

Regards Charles

Edited By Charles 2010 on 26/11/2010 16:09:17

[Charles 2010Participant @charles2010]

A chum of mine is designing a 555 timer strobe so that I can get a good idea as to when my engine is doing that sort of speed ..

 

If it is successfull I will let you know details via this forum ..

 

Regards Charles

Edited By Charles 2010 on 26/11/2010 18:00:56

[John Wood1Participant @johnwood1]

Well done Charles, it’s certainly getting there and all credit to you.  The governor spring needs to be lighter to run slower, and indeed to get it to open in the first place, I can run mine VERY slowly indeed and much less that 400rpm although 4 to 5 is certainly a decent working speed.  I picked up a small electronic strobe off the internet, it’s the type which triggers from a small piece of white reflective tape stuck onto the wheel, it all works fine and was not too expensive (about £20 as I remember). I thought about building one myself based on the 555 timer chip but felt my time was worth more to me so went for the easy commercial option.

 

Will you be trying it on gas at any time I wonder?

 

LA Services demo engine runs slowly but without hit & miss which, I agree is not the best way of demonstrating, I guess it’s less likely to falter when running continuously so that’s why they do it.

 

Have now moved house (at last) so no workshop yet.  Will get back into it probably in the spring.

 

All the best,  John

[Charles 2010Participant @charles2010]

Thanks for the comments John.

 

the strip down revealed the follow ing problems:-

1. that the main bearing had been moving in their seats – solution – the oilers have been made with M5 connection and this has been taken right into the bearings to prevent rotation.

2. the big end had slight end float  – solution – a slight filing of the end piece take up the slack

3. the speed lever did not allow operate – solution – much lighter spring used  and the minimum position noted

 

and also  the good points:-

1. that the piston is as good as new

2. that there is no wear noticed o nthe gudgeon pins and end caps

 

When all is bolted back down and photos taken it will have another run …

 

Regards Charles

[Anonymous]

Hi Charles,

 

Congratulations on getting the engine to run! Although I have already part machined the carb to the published drawings, if you don’t mind I’ll half inch your design instead. It’s a lot simpler. Thank you.

 

Regards,

 

Andrew

[Charles 2010Participant @charles2010]

Hi Andrew

 

I put the design on the forum so that other can use it ..  At the air entry end I did progressively bell out the end with 20 then 30 then 40 then 50 deg cuts which i hope you can make out from the pictures.  So I bored the first angle as stated and the just went in from the end so the the edge is quite thin .. Again I hope that can be seen from the drawing ..  I have also made a choke to go on the end …

 

the integral non return vave works a treat  but I do hope to make a bird feeder type fuel tank such that the level in the lower tank start just a small amount below the entry to the carb …  This is just thoughts at the momnet but the carb is proved.

 

If you want more detail let me know ..

 

Rgards Charles

Video can be seen here — follow the links on the pages to Economy engine  then video

Economy engine running

Edited By Charles 2010 on 27/11/2010 21:03:50

[Charles 2010Participant @charles2010]

Posted by John Wood1 on 27/11/2010 11:55:55:

 I picked up a small electronic strobe off the internet, it’s the type which triggers from a small piece of white reflective tape stuck onto the wheel, it all works fine and was not too expensive (about £20 as I remember).

 

 

 

Any more details you can give to lead me to the one you bought …??

[Charles 2010Participant @charles2010]

This is an improved drawing showing the “bell mouth air entry”  angle not important but create a smooth curve …

 

The lower unon is part of the the  non return valve, and as such has a CROSS filed into the flat to allow fuel to flow past with a lower section  that screws onto the M6 Thread with a small stainless steel ball bearing.

 

Regards Chalres 

[Charles 2010Participant @charles2010]

All being well I will be making up a base to bring the crank up to about 23″ from ground level, then may be add 4″ wheels which will bring it to about 24″  which should be a reasonable height from the gound  for starting and running.

 

It is being made from the steel angle and square section I have laying around so it will be put to good use …

 

Still think about the fuel tank !!!

 

Regards Charles

[Anonymous]

Hi Charles,

 

Thanks for the updated carb drawing. I’m not sure I understand the purpose of the non-return valve. I assume that air drawn thru the carb causes fuel to be sucked from the tank? Does the non-return valve stop it running back? At what level do you think the fuel tank should be relative to the carb? I’m planning to TIG weld an external stainless steel fuel tank, so I’ll have freedom to set it at what height I want.

 

Regards,

 

Andrew

[Author]

Posts