Laser 200 in line twin - retro fit

[Aldo Rebsamen]

Hi Jon,

thanks for explanation.  Great expertise as always.

 

Regards Aldo

[Steve Dunne]

Well - we now have a baffled engine - better than a baffled pilot, eh??

 

The starboard inlet has a baffle to direct air to the top (cold) side of the engine.

There is a baffle (2) to tunnel the air past the cold side. The air must then pass down through the cylinders to the exhaust side.

Then a baffle (3) is there to redirect air that has come down through the cylinders to the outside.

The exit hole in the cowl is baffled over the cold side of the cylinders to force the air down through the cylinders.

All comments (even rude ones) very much appreciated, this is new territory for me...

 

 

 

 

 

 

Ah well - we now

 

Steve.

[Ron Gray]

That is now very similar to mine on the Sportster, if you rotate it through 90 degrees and I didn't have any over heating issues with mine.

[Ron Gray]

Due to concerns that grit from our tarmac / concrete strip could be ingested, I have put filters on the carbs (thank you Mrs Gray).

 

[Gary Manuel]

All good stuff lads. Watching and learning.

[Ron Gray]

My 240v sucked up some grit and was rather expensive to fix so I don’t want it happening again!

 

[J D 8]

Think you need to fit some proper filters like the RC 4x4 buggy's use. 

I younger days I was a grass track racer [ not much grass about after the track had some use, just mud or dust ] One new chap joined the club with an old Ford Anglia, it would go well for the first couple of laps and then the power would drop right off and the rest of us would lap him before the race ended. In next race same again, it was was a right puzzle.

  We decided to see if we could help our clubmate. On opening the bonnet the answer was there to see, his air filter was just an old sock fixed over the carb much like your little filters.  What happened was as the race progressed dust particles would cover the sock restricting the air into the engine and upsetting the mixture. As soon as he stopped the dust fell off and engine was happy again.

  Not saying your motor would be so affected but the bits of cloth themselves could upset the motor.

  We also had one chap who's motor ran well at the start of the season but was soon smoking badly.   We soon found the problem, I recon the inside of his motor would have been much like your 240v. His filter was just a wire mesh kitchen strainer!  The stone trap we called it!  A well designed filter will keep the crud out without quickly clogging

 Cheers, John.

[Ron Gray]

Back in the day I used to fit nylon stocking filters onto the bell mouths of my Bonny engines but only during dry summer runs, enough to keep the dust out. It would be really good to find some RC car air filters that would fit a Laser but unless you know the exact dimensions it's almost an impossible task. Plus then you have to think about how much they protrude from the carb as the carb intake on a Laser usually ends up close to the firewall (not so the front pot on the in-line twin!). I will probably set about designing my own and 3D printing it but for now the 'stocking' filter will do, as, unlike grass tracking there is far less muck to worry about (pits, taxi out, take off and landing) so I don't think clogging will be an issue, I'm mainly trying to keep the larger particles from being eaten.

[Jon H]

it was at my request Ron give filters a try. The debris we are talking about is quite chunky grains of very sharp sandy material and they are not the recommended diet for anything mechanical. Also as we are trying to test this engine for reliability, external damage will not help us! 

 

Beyond that though i have been thinking of recommending filters for some time as the two most common types of damage we see are bearing corrosion/failure and debris ingestion. Both of these are more common than crash damage when it comes to engines on the bench for rebuild. 

 

The reason is simple enough. How often do we clean out the engine bays? not often i would wager, and certainly not after every nose over/trip into the weeds at the edge of the strip. All of that sort of thing accumulates dust and grit in the cowl and eventually it will find its way into the carb area. My poor Hurricane needs its face cleaned up after a belly landing last weekend. Its a chore, but i dont want to have to pay the boss for new engine parts! 

[Ron Gray]

And to reiterate, our site has a tarmac / concrete pits and runway over which farm vehicles travel so there is a layer of dust and grit that is difficult to get rid of. We do have a self propelled walk behind sweeper but that only gets rid of the larger lumps of detritus and really needs to be used on an almost daily basis, which isn't going to happen!

[Andy Stephenson]

It would be useful to have someone on here that does IC cars as they always use air filters. I have looked through what is available but they are always designated to particular engines so it's difficult to know what would fit an aero engine without a lot of buying and error.

[Manish Chandrayan]

5 hours ago, Jon - Laser Engines said:

it was at my request Ron give filters a try. The debris we are talking about is quite chunky grains of very sharp sandy material and they are not the recommended diet for anything mechanical. Also as we are trying to test this engine for reliability, external damage will not help us! 

 

Beyond that though i have been thinking of recommending filters for some time as the two most common types of damage we see are bearing corrosion/failure and debris ingestion. Both of these are more common than crash damage when it comes to engines on the bench for rebuild. 

 

The reason is simple enough. How often do we clean out the engine bays? not often i would wager, and certainly not after every nose over/trip into the weeds at the edge of the strip. All of that sort of thing accumulates dust and grit in the cowl and eventually it will find its way into the carb area. My poor Hurricane needs its face cleaned up after a belly landing last weekend. Its a chore, but i dont want to have to pay the boss for new engine parts! 

What effect will that stocking cover have on the effective air intake area and performance of the engine? Not just for this particular engine but in general?  

[Ron Gray]

i'll let you know hone I've run it later on this week! But I don't think they will effect the tuning that much, a tad richer possibly.

[Ron Gray]

Flew the Sportster today (more very windy conditions) and re-tuned as it was a little too rich with the filters in place (as expected). Flew it without the cowl on to allow me easing adjusting - vid to follow.

[Ron Gray]

First part of tuning flight vid - apologies for the sound of ethnic wind, it was a bit strong again today!

 

 

[Ron Gray]

Part 2 of the vid

 

 

[Dwain Dibley.]

Seems to be as sweet as a nut now Ron. ?

D.D.

[Ron Gray]

It was D.D. until I put the cowl back on then it was running slightly too rich. I'm going to play around with air intakes to see if I can feed the carbs directly from outside air.

[Dwain Dibley.]

You need to get the inlet out side the cowl, like I did on my 26 cc Zenoah , in my cap 232. Also you can get calm air from inside the fuselage, with a tube from the carb. (petrol tho)

D.D.

Can't find the 26 but here is the 45. I know yours is Glo but the principles of cowl turbulence must be the same. ?? with out this on she would cut in a roll.

Edited April 30, 2021 by Dwain Dibley.

[Ron Gray]

Yes, something like that D.D. but a couple of inlets set further back in the fuse to allow for the tube to rear facing carbs to go straight back then curve out. The one for the rear carb will have to go through the firewall and I need to make sure that both tubes are the same length. Goodness knows if it will work, I can’t really try it before cutting as the inlet to the rear carb is too close to the firewall to allow the tube to curve, so an evening of humming and haaing!

[Steve Dunne]

Ron, for interest, I had air feed problems at first, the rear carb going very rich, dragging the revs down, then rising back again, cycling over a 1½ - 2 second cycle.

This was apparently due to turbulence around the rear carb, very close to the firewall.

I gouged out a 5mm deep, 20mm wide depression in the firewall directly behind the rear cowl, and used silicon caulk to sculpt a bit of shape around the area.

The problem did not recur.

Steve.

[Ron Gray]

Interesting Steve, did you fly it without the cowl at all?

[Steve Dunne]

No, it is donkey's years since I flew any aircraft without the cowl.

Most warbird and other big cowls are quite heavy, so affect the balance, and can change the aerodynamics as well as the engine performance.

I prefer to go with the cowl from the start, even though it can be a nuisance at times having to remove it to fiddle between flights!

 

YMMV ?

 

Steve

[Denis Watkins]

On 25/04/2021 at 18:00, Ron Gray said:

My 240v sucked up some grit and was rather expensive to fix so I don’t want it happening again!

 

 

I have some various grades of phosphor bronze mesh Ron,

fine and very very fine, can be cut with scissors and fit in an envelope,

which I gladly donate to your quest

just PM me as to where you want this delivered

To make filters I meant to say

Edited May 1, 2021 by Denis Watkins

[Ron Gray]

I was looking at the engine bay today and noticed that it was quite possible for the crankcase oil breather pipe to get caught in the mouth of the rear carb and wondered if this was the cause of my slight irregular running. So I’ve clamped it back to the firewall and plan to take the model out again tomorrow to check it.