Newbie Question 1/4 HD motors

[boomer999]

Hi there everyone. This will be my first attempt at a 4 stroke engine. Up to know I have just tinkered with sterling engines. And I have a few questions to start with. I am sure there will be more along the way. Be patient with me please. I am sure some of these will really seem basic to a lot of you here.

I am in the process of having a a 3d copy 1/4 scale printed up of two Harley Davidson crank case half's that I will use for casting the block.

Just thinking ahead a bit. And I was wondering about what aluminum stock to use for the pistons. And how you decide on the ring tension. Is there a guide line to use? So many .001 oversize to the bore? And what material is used for the rings.

For the cam and crank bearings. Is there a specific brass I should be using?

For lubrication, I was counting on having to replicate the oiling system(seems challenging) Am I wrong? is there another approach? If the oiling system is replicated as well, what oil should be used? Synthetic? and the weight?

What fuel is commonly used in these engines?

Looking forward to doing this project and trying to overcome the many challenges that will surely present themselves. As I move forward building this 1/4 model engine, I will be simultaneously be rebuilding my Harley motor at the same pace as the model engine.



Thanks for your time. I look forward to reading your responses.

Boomer999

Hobby machinist/Electrician

 

[Cogsy]

All these answers are just based on my own experience and others will have varied opinions. I use whatever aluminium I have on hand for pistons. For the rings I use cast iron but many use viton O-rings with success in I.C. engines. I make my rings on size to the bore then split them. For the tension I use the appropriate sized 'wedge' recommended by a plans for similar sized pistons (I have a few plan sets with varying piston sizes so I select the closest one) then heat treat them.

For the bearings you can use machinable brass or bronze would probably be a little better. You can buy bronze bushes from bearing supply places and machine them to size if it's easier, this ensures you're using a good bearing material.

Many people run these engines on petrol/gasoline (often with a little lubricant mixed in) or a Coleman-type fuel. Some run them on propane. Personally I just use petrol with a little WD40 mixed in.

For lubrication you can replicate the original system, or a more simplified version, or alternately just rely on splash lubrication by building a tang on the bottom of the conrods which dips into an oil bath as it rotates.

I'm looking forward to watching your build.

 

[boomer999]

Thanks for your help. I am not sure what a piston wedge is. Is that something that is used on model engines? I have built countless v-8's and have never even heard of a piston wedge. On actual V8's that I have done in the past, I sized all of the rings with a ring grinder to a specific ring gap. Never had to worry about the tension, just had ensure the appropriate ring gap. And if I was to use viton o rings instead, how is the bore sized in relation to the o-ring.


I have enclosed a picture of the sterling engine I am presently working on. There are two power pistons that will be on the back side of the motor run off of a cam on the back side of the crank. there will be two brass rockers hanging below the motor running them. I have built a small alternator that is on the front side of the crank that will run the red and blue LED lights that I have machined into the motor base, its wiring is internal. The motor block has been drilled for internal wiring, and the stand has channels in it to run the wires. If you look underneath the motor, you can see all of the wires hanging under the base. I use fondue fuel on my sterlings. The fondue fuel goes into the heads(i still have to build the top of heads) and will be ignited by custom made spark plugs, ignited by a powerful furnace ignition coil.

Here where I get a little silly. This thing will have an automated start. Hit the button, and through a series of timed relays, it should start on its own. I have a Lithium ion battery for it to run the ignition system, as well as a small solar panel and solar buddy to keep the ignition in a state of readiness lol.

The first relay will ignite the fuel and allow a few seconds for things to warm up. Then the second relay will raise an electric motor up against one of the flyweels to give it a spin and get everything going.

 

[stevehuckss396]

Just thinking ahead a bit. And I was wondering about what aluminum stock to use for the pistons.

I use 6061 or 7075, whatever is on hand. 6061 are made .001 to .0015 smaller than the bore. 7075 are made .00075 to .00125 smaller than the bore.


how you decide on the ring tension. Is there a guide line to use?

I use the George Trimble method where a fixture is mad to hold the ring to the proper dimension and then heat treated. Just covered the rings in my Pacifier thread.



So many .001 oversize to the bore?

.0005 - .0000 but not under size



And what material is used for the rings.

I use 12L14 steel liners, Aluminum pistons, cast iron rings


For the cam and crank bearings. Is there a specific brass I should be using?

Ball bearing or Bronze is best, dont use brass.


For lubrication, I was counting on having to replicate the oiling system(seems challenging) Am I wrong?

Yes it's challenging but go for it.



is there another approach?

Splash oil systems are used in many small engines. I also put a little WD40 in the fuel just to be safe.


If the oiling system is replicated as well, what oil should be used? Synthetic? and the weight?

I use 10W40 of what ever is on sale.


What fuel is commonly used in these engines?

Coleman lantern fuel is real popular. I run Turbo Blue racing fuel (Gasoline). Smells better and half the price.


Stevehuckss396

Hobby machinist/Electrician

 

[stevehuckss396]

Forgot to tell you in the other post but you engine tipped over. Rof}

 

[Cogsy]

I am not sure what a piston wedge is. Is that something that is used on model engines?

It's a physical wedge used to spread and hold the ends of the ring apart while heat treating them. Once treated the wedge is removed and the rings stay 'sprung' open. This is the method I use for ring tension.

 

[boomer999]

Lol Ya I know. I Don't know what gives. Its upright on my computer. But goes side ways when I up load it here. I did it twice.

Thanks for all the info and help. Sure learning a lot. I was just looking at you little demon V8 today. Its on the to do list now lol.

 

[boomer999]

Thank you again for the info. I am sure I will be asking a lot more along the way.

 

[boomer999]

Did I read that right Steve. Are you an electrician as well?