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Rumely Oil Pull engine

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JasonB11/11/2020 14:16:00
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I don't think mine are anything special about the £10mark sounds right, 3 stone at that size.

For 30mm I would say you could go with a BS120, 3.12mm wide groove and 2.5mm deep

John Rutzen11/11/2020 17:36:29
317 forum posts
16 photos

Thanks Jason, I'll get one ordered.

John Rutzen25/11/2020 12:12:19
317 forum posts
16 photos

I have a query regarding the fitting of the ball bearings on my crankshaft. I was going to fit the outers in the housings using loctite bearing retainer but i want to ensure that the inners don't creep on the crankshaft. Or am I being a bit pernickety? I would have liked them a bit tighter than the fit I achieved but perfection is rarely attained in model engineering so I wondered if there is anything I could put on the shaft that would prevent rotation but still allow me to dismantle it easily. The ball bearings are doubled each side and are 17x 35x10.

Howard Lewis25/11/2020 13:59:29
4683 forum posts
10 photos

Thinking about "Pull Rods" for the valves, how about a lever follower, under the cam. with a refined form of clevis on the pull rod?

Was that how the real engine did it?

Otherwise, the spring arrangement shown provides the opening force for the valve by keeping the follower in contact with the cam. and then if the linkage is secured to the valve, as a valve spring to hold it on the seat..

Or was the cam internal, with the pull rod external to the follower?

Howard

John Rutzen25/11/2020 19:42:47
317 forum posts
16 photos

Hi Howard, yes the original cams were internal. What I have decided on is as you suggest, a lever follower under the cam with a bell crank action to pull the valve rod.

John Rutzen16/02/2021 09:42:40
317 forum posts
16 photos

Hi everyone,

i am getting on well with my Rumely engine and pretty near testing it. However there doesn't seem to be much compression. I worked it out by calculating the volume of the head space and having read that it shouldn't be too high I worked it out for 6 to 1 but I don't think it's anywhere near that. I got me to wondering why we need compression? There is nothing about it in ET Westbury's book as to the reasons for it. Does anyone know why we need compression in petrol engines?

John

Roger B16/02/2021 11:37:05
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138 forum posts
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Compression allows for higher output and efficiency. The higher the cylinder pressure before ignition the greater it will be afterwards increasing the force on the piston and hence the output. The efficiency of an engine depends on the temperature difference between the maximum temperature at combustion and the exhaust temperature. The greater the diference the higher the efficiency. The maximun temperature and pressure are related which is why diesel engines with a high compression are mor eefficient then petrol engines which need to run lower compression to avoid pre-ignition.

For model engines the actual compression is not so important what is critical is that there should be minimal leakage. You say that you don't feel much compression. Does it feel 'springy'? Can you bounce the piston off the compression? This engine is a little smaller than yours but will hopefully give you an idea of what I mean.

**LINK**

John Rutzen17/02/2021 12:34:12
317 forum posts
16 photos

thank you Roger, there isn't any bounce on the compression so I am having another go at seating the valves. Leaking valves is the problem. I think I may have to add a bit onto the piston as well to reduce the combustion chamber space.

not done it yet17/02/2021 14:36:02
5790 forum posts
20 photos

The compression ratio for some engines of that era were not high. I have come across engines with a CR ratio of 4.1:1.

That may not be appropriate to a small scale model, mind.

Andy_G17/02/2021 15:37:30
118 forum posts
Posted by not done it yet on 17/02/2021 14:36:02:

The compression ratio for some engines of that era were not high. I have come across engines with a CR ratio of 4.1:1.

That may not be appropriate to a small scale model, mind.

My little horizontal engine is designed with 4:1 compression ratio, and runs quite happily with noticeable compression/bounce when flipped over (~21mm bore).

Leaky valves seem a likely suspect.

not done it yet17/02/2021 16:59:15
5790 forum posts
20 photos
Posted by Andy_G on 17/02/2021 15:37:

My little horizontal engine is designed with 4:1 compression ratio, and runs quite happily with noticeable compression/bounce when flipped over (~21mm bore).

Leaky valves seem a likely suspect.

One, that I was thinking of, was about 117mm piston diameter and 5.2 litres capacity.🙂. Even if the valves/piston rings leaked slightly, they would still start quite easily.

Andy_G17/02/2021 17:03:56
118 forum posts
Posted by not done it yet on 17/02/2021 16:59:15:
One, that I was thinking of, was about 117mm piston diameter and 5.2 litres capacity.🙂. Even if the valves/piston rings leaked slightly, they would still start quite easily.

Yeah, I suspected something as such.

I was seeking to address the "may not be appropriate to a small scale model" concern

br17/02/2021 17:20:15
465 forum posts
4 photos
Posted by John Rutzen on 17/10/2020 10:46:33:

Hi, I'm working on the design for an engine for a Rumely tractor that I want to build. There are no drawings but I have got the major dimensions from an owner in America. I am working out the engine from photos, catalogues, videos and anything else I can get hold of. It is a single cylinder 30cc. What I want to ask is can i fit a C.I. liner in an aluminium block? Also I am thinking of posting the drawing before I make anything for constructive criticism please. I don't do CAD so I'm not sure how I can do this. Maybe just take a photo of it, i'll see how it works out.

John

Good to see something a little different being tackled

Looking forward to progress reports / photos

Bill

br17/02/2021 17:20:16
465 forum posts
4 photos
Posted by John Rutzen on 17/10/2020 10:46:33:

Hi, I'm working on the design for an engine for a Rumely tractor that I want to build. There are no drawings but I have got the major dimensions from an owner in America. I am working out the engine from photos, catalogues, videos and anything else I can get hold of. It is a single cylinder 30cc. What I want to ask is can i fit a C.I. liner in an aluminium block? Also I am thinking of posting the drawing before I make anything for constructive criticism please. I don't do CAD so I'm not sure how I can do this. Maybe just take a photo of it, i'll see how it works out.

John

Good to see something a little different being tackled

Looking forward to progress reports / photos

Bill

John Rutzen17/02/2021 17:40:50
317 forum posts
16 photos

I've added a some metal to the piston and it definitely bounces off compression now. I'm using Jan Ridders design blokker ignition and have made my own spark plug as well so I should be set for a test in the next week or two. I've used E T Westbury's road roller carb so hope it all works.

John Rutzen23/02/2021 18:44:40
317 forum posts
16 photos

Hi, please could someone tell me if I should add oil to the petrol for a model four stroke? I've seen references to adding castor oil but I would appreciate some advice. Thank you.

JasonB23/02/2021 18:50:51
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I only add oil if it's an open crank engine with no drip oiler to lubricate the cylinder/piston. Even then it's just a couple of drops of 2-stroke oil to 50mls fuel.

not done it yet23/02/2021 19:25:44
5790 forum posts
20 photos

Why not? Upper cylinder lubricants were quite common 40-50 years ago. Redex comes to mind from years gone by.

John Rutzen26/02/2021 15:24:40
317 forum posts
16 photos

Hi Everyone. success today! I got the Rumely engine running. I had a leaking exhaust valve so I remade it in a cage and left a sharp edge for the valve. I then lapped it in very lightly with Solvol Autosol and got it to seal. I got it to start by injecting neat petrol into the inlet. Once started it picked up and now the problem is it goes too fast! I can't get it to tick over so any help appreciated please. The carburettor is to ETW design for his road roller and the fuel tank is about 3 inches below the carb. I just scaled it up by 1.5.

Another question- how can i measure the speed? It just looks frighteningly fast to me.

Roger B26/02/2021 17:13:19
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138 forum posts
56 photos

Congratulations thumbs up

I would suggest that you raise the fuel tank so that the fuel level is maybe 1/2" below the carb. There may not be enough suction at low speeds.

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