Laser Engines - Technical questions

[Rob Tothill]

Thanks Jon. I'll give it a polish and try again.

[Ron Gray]

Has anyone tried running a Laser with a flexi exhaust in place of the standard silencer, and if so what was the noise like? The reason for asking is because I have a 100 that I want to fit to a new build (Seagull Radial Rocket) and the flexi exhaust would be a better fit than the standard silencer.

[Alan Hilton]

Hi Ron

I have two v twins on flexeible exhaust both run well but they are louder than standard item . Our site isn’t noise sensitive and the do sound nice ,a bit like a Harley Davidson

Alan

[Ron Gray]

Thanks for that Alan. We don't have a noise restriction, as such, on our site but we do have to be aware of noise and try and keep it to a minimum. I'm currently running another 100 in another 'plane and that, with the standard silencer, is very quiet so I'm hoping that the noise increase with the flexi pipe won't be too bad. Having said that, I will be running smaller prop (for speed) and to a certain extent I want a bit of noise, after all, it is a Reno Racer! If it proves to be too much I could always make up an adapter and fit the silencer to the end of the flexi pipe.

[Alan Hilton]

Hi Ron

Mick Reeves does Laser fit flexible pipe which works well .He also does a silencer which fits the flexible .I haven’t tried the silencer but it must reduce the noise and may be worth a go

Alan

[Ron Gray]

Took the Radial Rocket to the field today for its maiden flight. I was little bit apprehensive about the engine exhaust arrangement, with no silencer I was concerned that it may produce too much noise. I needn't haven't worried, even without the silence the noise level was more than acceptable and the exhaust note was very pleasant, a colleague commented that at half throttle it sounded like the real thing! So a big smile on my face then, next up is to change the prop from a 14x6 to a 13x7 to see what difference that makes, although the 14x6 does propel it along at a fair old lick.

[Chris Walby]

Jon,

Finished the Acrowot Laser build and was going to fly it without the cowl, then realised I need to get it noise tested so fitted the cowl, but then remembered I have attached the forward facing tank vent to the lower engine mount.

As this is now inside the cowl will it be an issue? There are a couple of large holes in the front of the cowl to let air or does the vent really need to be outside and in the airflow?

Cheers Chris

[Jon H]

the biggest problem is that it will fill the cowl with fuel as it is the vent line for filling the tank. beyond that it will probably be ok but it wont work as well as it would if it were dangling in the breeze

[Chris Walby]

Jon,

Good point about filling as I fill via the carb line and just watch the vent line to ensure my counting in (and later out/refill) is right until full.

I'll move it to the outside and then I'll never need to go in the cowl again!

PS I don't let any of the tank vent lines dangle in the breeze as I thought the "preferred option" was forward facing to give a little positive pressure?

On a different subject regarding inverted Lasers, I plumbed the crankcase vent down like the horizontal installations. In your experience does oil come out of the vent line? or could it just be directed upwards and just act as a air vent?

Cheers

[Chris Walby]

Thought I would take a photo and now I am not so sure....!

[Manish Chandrayan]

Chris if that's the tank vent I don't see any issues.
But if that's the crank case vent I see the cowl and firewall getting a nice coat of used lube

[bert baker]

This is a great example of how it should be done,,,,not done by me but came on a Old sopwith pup,,, it’s a Laser 180,

Tank vent is in forward facing position in flow of prop wash,waste crank vent oil is collected in a Old pill tub,camera film containers work well.

[bert baker]

It is over propped but runs superb...even being over propped it runs so sweet,, it has never missed a beat or cut out

Edited By bert baker on 22/09/2018 09:52:19

[cymaz]

Posted by bert baker on 22/09/2018 09:45:50:

It is over propped but runs superb...even being over propped it runs so sweet,, it has never missed a beat or cut out

Edited By bert baker on 22/09/2018 09:52:19

You can hear the engine above the pilot shouting, “attack, attack, attack....ratatatatat”

[Jon H]

Chris i recommend you glue a small wooden block inside the cowl and then drill through it. The pipe can then be glued into the block. Its quick and really simple, just make sure you dont kneel too close when filling or you may end up with a lap full of fuel!

[Tim Flyer]

Hi guys just a question while trying to put the prop and spinner on my Laser 180. The crankshaft is too short to use both the bolt and spinner adapter with either a fairly thin hub just engines 18x8 wooden prop, or a thicker hub APC. The engine came with a heavy duty “shaft bolt” which I believe would extend the crankshaft. However that is about 12mm diameter and larger than my 10mm prop reamer. I wouldn’t trust myself to properly centre a 12mm hole with a pillar drill. Are there larger  prop reamers available? When I use the shaft bolt I would need to buy another large bolt with a centre tap to screw into it I guess. I don’t think my engineering is up to that . If I do use the supplied shaft bolt it will also need shortening or adding an extra washer to make sure the wooden prop is held tightly against the drive plate. I guess a simple alternative is buying a heavy duty spinner adapter )to act both as prop nut and hold the spinner. It would be nice to have a thin nut to lock this against. Anyway suggestions welcomed

Edited By Tim Flyer on 24/09/2018 09:47:54

[Ron Gray]

With my 180s I've done away with the nut and just used the 'shaft bolt' as you put it, this locks up agains the washer and is more than adequate (used this method on both glow and petrol 180s). The problem you are then faced with is the fixing of the spinner bolt. I used a 10mm bolt then drilled and tapped that for the spinner bolt, works a treat.

[Tim Flyer]

Cheers Ron I will do that . How did you ream the prop? . I was thinking of maybe putting a drill bit in the vice? Unless there is a better method as my reamer goes only up to 10 mm. I should be able to tap a 10mm bolt ok ad that seems the logical way to hold the spinner . Just a bit nervous of getting prop centre wrong.

Edited By Tim Flyer on 24/09/2018 10:13:38

[Jon H]

The hole is 13mm Tim and 13.2 reamers give a nice clearance in wooden props. Ron has already explained the other half of the job and i do the same with 10mm bolt drilled/tapped and then stuck in the end.

At some point we will offer these as its not exactly hard to make.

[Ron Gray]

No, don't ream the prop for the 'shaft bolt' that will tighten up against the prop washer in the normal way, all you are doing is not using the 'shaft bolt' as a prop nut. I'll nip out to the 'hanger' and take a pic for you. Be back in 5 mins!

[Ron Gray]

Here you go

[Bob Cotsford]

On my Lasers I used to just use the spinner adaptor as the primary nut to hold the prop on, Just Engines can supply the required thread combinations to suit the engine and 4 or 5mm spinner bolts. They never let go even using an electric starter (sorry Jon )

Edited By Bob Cotsford on 24/09/2018 10:42:08

[Tim Flyer]

Aha 😊Thanks Ron. I now see what you mean. That makes sense . I see I could just use the standard 10mm shaft hole and mount the shaft bolt on the end using the standard 10mm washer.. That saves me getting a 13.2 reamer. Those just seem to be available in specialised woodwork shops and not in the standard stepped reamer t.handle versions . Cheers Bob Thanks too . I have used the standard just engines spinner adapter and I bought one for this but the version I have is mild steel(spinner adapter) as I was planning to use a nut too, so I didn’t fancy the mild steel torqued up on a wooden prop in case it slips . They do make hard steel versions which I have used successfully .

[Jon H]

I probably wouldnt recommend using the sleeve nut as Ron suggests as the prop washer is likely to bend with all of the retaining force in the middle. It would be much better mounted the other way round with the fat end on the washer.

Its still not ideal however as the leverage wont do the crank any good in the event of a crash, but if you dont plan to crash then turning it round will be ok

[Ron Gray]

Whilst my prop washers haven’t bent, after all I’m using the Laser supplied ones () I would agree that the sleeve nut would be better mounted ‘tother way round. Leverage in a crash could be a thing, best not show the lump of brass that is the sleeve nut / nose weight fixed to the 180 in the Harry Kane then!