Author Topic: Roy's Little Engine  (Read 48584 times)

Offline b.lindsey

  • Global Moderator
  • Full Member
  • *****
  • Posts: 13860
  • Dallas, NC, USA
    • Workbench-Miniatures
Re: Roy's Little Engine
« Reply #45 on: December 19, 2017, 02:41:25 PM »
Nicely done Jo. This one is really moving alone rapidly!!

Bill

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: Roy's Little Engine
« Reply #46 on: December 19, 2017, 03:55:44 PM »
Almost look a bit too large a PCD but better than the Mecanno ones which would have been even larger as they are 38DP. A bit of fettling of the cast lug will have it looking central ;)

Offline Alyn Foundry

  • Full Member
  • ****
  • Posts: 1653
  • North Wales, Great Britain.
Re: Roy's Little Engine
« Reply #47 on: December 19, 2017, 06:13:36 PM »
Progressing nicely Jo.

In the mid 80's I would have been considered a " nube " and the use of both cheap and cheerful was the first choice. I think the Meccano gears I used for the prototype were Brass and 50:25 tooth, the 50 tooth wheel being 2 soft soldered together to get some thickness!

Once production started I discovered HPC Gears Ltd and used their  40 DP 52:26 combination. This gave a near 1" centre distance that had been used previously.

The cast lug, as Jason suggests, can be filed to look nice, it was made large to accommodate an idea that wasn't drawn. I fitted a larger metal boss with an eccentric tapped hole so that the gear pair could be finely meshed. A small grubscrew placed vertically downward locked the boss in position.

The crank gear on my engine is driven by a small pin secured into the crankshaft. I didn't like the idea of the governor slider being run over a keyway. The pin is unseen as the gear slips over it, making for a clean look.

Cheers Graham.

Offline Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 15294
  • Hampshire, england.
Re: Roy's Little Engine
« Reply #48 on: December 19, 2017, 07:01:44 PM »
Thanks Graham, I might do that.

I have been thinking about the larger gear and I had made it so that the cam is part of the Cast Iron but I think I will make the cam separately in Silver steel and harden it before fitting it to the gear.

Jo
Enjoyment is more important than achievement.

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: Roy's Little Engine
« Reply #49 on: December 19, 2017, 07:06:49 PM »
I have done quiet a few Hit & Miss engines that have the timing gear stud in an eccentric bush, if it's good enough for the full size it is good enough for our models. If the engine does not have that facility as ours don't see much wear I just set the backlash up on the mill and drill to suit.






Online crueby

  • Full Member
  • *****
  • Posts: 18557
  • Rochester NY
Re: Roy's Little Engine
« Reply #50 on: December 19, 2017, 07:13:31 PM »
Jason, I like that trick of setting the backlash with the gear held on the mill spindle, gives you the setup directly for drilling. I had always used the clockmaker-style gear meshing tool, which was used to scribe the position, and requiring setting it up to drill on that mark. I like your way better!

Offline Alyn Foundry

  • Full Member
  • ****
  • Posts: 1653
  • North Wales, Great Britain.
Re: Roy's Little Engine
« Reply #51 on: December 19, 2017, 07:54:04 PM »

I have been thinking about the larger gear and I had made it so that the cam is part of the Cast Iron but I think I will make the cam separately in Silver steel and harden it before fitting it to the gear.

Jo

Hi Jo.

Well, the decision is ultimately yours but you could simply machine the cam profile using your rotary table and then heat and oil quench the gear for a mild hardness.

Don't forget that the cam follower is made from Brass and is going to wear much faster than the cam. That is of course if you're going to the drawing. Many builders altered the round pushrod to a rectangular one, more in keeping with traditional agricultural engine's of the period.

Whilst we're on the subject of pushrod, are you going to try the improved method of exhaust valve operation?

The drawing shows the nearest valve to the pushrod being operated, at the time I used a fabricated carburettor that screwed into the side face of the cylinder head with the exhaust coming out below. Well....
I found that the engines vibration shook loose the non return valve and before fuel got back to the jet it would stop. My improvement was the little Iron casting for a " tank top " carburettor that entered from below and the exhaust left through the side. The only difference is that the rocker arm is bent and extended over the atmospheric inlet valve. This single change, to my mind made the R.L.E. look far nicer than previously.

Cheers Graham.

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: Roy's Little Engine
« Reply #52 on: December 19, 2017, 08:00:49 PM »
What the man says, don't think any of the hit and miss engines I have done called.  for a hardened cam, it is not as thought they are running at the revs you get on a 4-stroke aero engine. Suppose a quick coat of case hardening powder on running surface of an integral cam would not hurt if you want it hard.



EDIT, having said that all the cams have been steel and not iron

Offline Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 15294
  • Hampshire, england.
Re: Roy's Little Engine
« Reply #53 on: December 23, 2017, 08:57:49 AM »
Whilst we're on the subject of pushrod, are you going to try the improved method of exhaust valve operation?

The drawing shows the nearest valve to the pushrod being operated, at the time I used a fabricated carburettor that screwed into the side face of the cylinder head with the exhaust coming out below. Well....
I found that the engines vibration shook loose the non return valve and before fuel got back to the jet it would stop. My improvement was the little Iron casting for a " tank top " carburettor that entered from below and the exhaust left through the side. The only difference is that the rocker arm is bent and extended over the atmospheric inlet valve. This single change, to my mind made the R.L.E. look far nicer than previously.

Cheers Graham.

 :facepalm: Here am I getting constant  :stickpoke: because some of my IC engines don't run and I am building the RLE as it is an "easy" build as I was told that even I can get it to run and now it seems that this is not going to be a simple build  :ShakeHead:

Maybe I will go back to my aero engines.

Jo
Enjoyment is more important than achievement.

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: Roy's Little Engine
« Reply #54 on: December 23, 2017, 10:12:05 AM »
Can't be that much more complicated to screw the carb and silencer into each others holes and make a rocker arm to bend over the inlet valve or do you need a casting for that ;)

Sounds to me like the modification will help with running so worth doing. It is also the more common layout on the horizontal hit and miss engines, think almost all the ones I have done have the exhaust on the opposite side to the pushrod though bottom carbs are common.

Offline Manorfarmdenton

  • Full Member
  • ****
  • Posts: 124
    • Fearnley Contract Services
Re: Roy's Little Engine
« Reply #55 on: December 23, 2017, 11:16:50 AM »
Graham, is there anything to be gained by altering the compression ratio of the RLE from the original drawing?  My drawing suggests a higher compression alternative but I'm wondering what effect it would have on starting or running.
Jason, thanks for the suggestion - I belong to this group but seem to look at Smokstak  ::)
John Fearnley

Offline Alyn Foundry

  • Full Member
  • ****
  • Posts: 1653
  • North Wales, Great Britain.
Re: Roy's Little Engine
« Reply #56 on: December 23, 2017, 11:47:23 AM »
Jo,Jo don’t despair.

The modification is dead easy.

The rocker arm starts life from 1/4” by 1/4” BDMS. In my early days with no milling machine the reduction was done with a file. In fact number 103 was built entirely without the use of a milling machine!

I’ll post a closeup photo of the arrangement on 103 later on today.

Number 103 is actually, quite unique. It started out as an air cooled engine and was exhibited on the northern vintage engine circuit. Also advertised as a kit in various periodicals. Zero sales. After the water hopper had been suggested I set too on patterns. My first attempt at the cylinder was a complete, well not quite, failure. I hadn’t taken into consideration how to attach the cylinder head! The casting you bored and honed has a couple of rings sticking out to provide the cylinder head with a fixture, the middle ring can be used to stop the hopper from rotating. Number 103 has no such rings. I had to make a rather complicated tie bar set to pull the head against the hopper and cylinder. Oh, and then there’s the lubricator, mine’s the only one on a stalk. I hadn’t given sufficient width for the 1” by 1/8” BSP oiler! A new and better thought out pattern was made, the rest is history.

Cheers Graham.

Offline Alyn Foundry

  • Full Member
  • ****
  • Posts: 1653
  • North Wales, Great Britain.
Re: Roy's Little Engine
« Reply #57 on: December 23, 2017, 11:58:35 AM »
Hi John.

Increasing the compression ratio on the R.L.E. won’t make starting it any more difficult it will just increase the power output fractionally.

I had been commissioned to build one to drive a dynamo, I found that it coped better with the extra 1/4”.

If you’re just wanting it to run as an engine I’d suggest leaving it as per drawing.

Cheers Graham.

Offline Alyn Foundry

  • Full Member
  • ****
  • Posts: 1653
  • North Wales, Great Britain.
Re: Roy's Little Engine
« Reply #58 on: December 23, 2017, 01:54:51 PM »
As promised.

103 has spent the summer cutting wood at the Anson Engine museum.

Offline Manorfarmdenton

  • Full Member
  • ****
  • Posts: 124
    • Fearnley Contract Services
Re: Roy's Little Engine
« Reply #59 on: December 23, 2017, 01:58:27 PM »
Thanks Graham - I knew you'd have the answer.  As Jason knows, I have made life a bit more difficult for myself by using the cast-iron 3-ring piston designed for a Red Wing, simply because I already had the necessary jigs.  Its slightly longer from gudgeon pin to crown than your design, so if I use your dimensions for the con-rod the compression will be slightly higher, or I can make it shorter for lower compression.  John.
John Fearnley

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal