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Laser Engines - Technical questions

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Martin McIntosh22/11/2019 09:56:02
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3412 forum posts
1202 photos

I remember asking Jon about the possibility of a 50 ish motor to replace the very noisy 2st petrol in my Hurri. a few years ago. It would have to turn a 23x8 at at least 6000rpm though. The idea of a very narrow angle in line V appeals to me.

Jon - Laser Engines22/11/2019 10:01:19
5501 forum posts
268 photos

No im still here, just about hanging on to my sanity.

Ron, this is what i want to make. Boss says its too complicated. Pretty much sums up the whole story here. Why do something awesome when the bare minimum will do? Anyway, im working on it and i will offer left handed versions of the spanners

Reverse engines are a pain and not worth the hassle but reverse spanners seem reasonable.

bert baker22/11/2019 10:10:56
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1609 forum posts
331 photos

Oh well,, I’m off for now,

Good luck and see you in the summer

Ron Gray22/11/2019 10:16:16
2154 forum posts
937 photos

@Jon - what, one flat bar with a couple of hex cut outs in the centre and an end that fits a glow plug complicated, I would swear but not allowed to on this forum!

David P Williams22/11/2019 11:40:19
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913 forum posts
318 photos

Bert - if you want to sell the 7-77 I have a Flair Stearman kit waiting for itsmiley

bert baker22/11/2019 12:45:02
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1609 forum posts
331 photos
Posted by David P Williams on 22/11/2019 11:40:19:

Bert - if you want to sell the 7-77 I have a Flair Stearman kit waiting for itsmiley

7d1a4c22-d8a3-443a-b1ab-20dbfe3a71ea.jpeg

bert baker22/11/2019 12:45:48
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1609 forum posts
331 photos

It’s on the front of a Zorroli Stearman

Jeremy Scott-hake22/11/2019 21:20:34
18 forum posts
3 photos

Please can I have a plug spanner .

Thank you Jon

Martin McIntosh22/11/2019 21:44:38
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3412 forum posts
1202 photos

Best plug spanners in the world came with MDS engines would you believe!

Paul james 817/12/2019 13:55:12
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174 forum posts
48 photos
Posted by Jon - Laser Engines on 19/11/2019 08:26:07:

Paul your short 90 is actually an 80, or perhaps a very late 75 like your other example.

The 80 was just a bored out 75 and the 100 was a bored 90. A simple check is to see if the piston from the 90 fits, if so its a 75, if not its an 80

I was trying to see if there was anything stamped on the mounting lugs that would give a date of mfr and help pin down the size but the photos dont show it.

Hi Jon,

Just clearing up my office and found the piece of paper I wrote down the engine sizes on while I was rebuilding them (for some odd reason quite a few didn't seem to have the capacity marked on them?)

The taller one was Bore: 26.5mm Stroke: 27mm

The shorter one was Bore: 28.7mm Stroke: 22.9mm

I still make them both around 0.9 cu inch.

Jon - Laser Engines17/12/2019 14:20:28
5501 forum posts
268 photos

hi Paul

The taller engine is an old 90. The shorter one is an 80 as it will have 27.7mm bore and 22.2 stroke. We have never used a 28.7 bores or 22.9 strokes on any engine.

Martin Harris17/12/2019 15:04:24
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9333 forum posts
249 photos

Any possibility it could be one of the African made knock offs? Those dimensions are close to 1.25" x 0.9" if that might be significant.

Jon - Laser Engines17/12/2019 16:59:01
5501 forum posts
268 photos
Posted by Martin Harris on 17/12/2019 15:04:24:

Any possibility it could be one of the African made knock offs? Those dimensions are close to 1.25" x 0.9" if that might be significant.

i think they only cloned the 150 and they should be 26.9x33.5 bore/stroke

Andy Stephenson17/12/2019 18:27:28
169 forum posts
28 photos
Posted by trebor on 14/12/2017 18:23:24:

I'll start this off then ! Can you take the end of the silencer to clean the inside out or is it pressed in ? Ps Thanks for the advise earlier and I'll post a picture of the engines after I've finished cleaning I forgot the worst bits the silencers crook

Trebor,

When I asked Neil Tidy how to clean a Laser silencer, he said to put a 3/8" drill down the tail pipe and drill out the crud.

Andy.

Jon - Laser Engines17/12/2019 19:58:41
5501 forum posts
268 photos
Posted by Andy Stephenson on 17/12/2019 18:27:28:
Posted by trebor on 14/12/2017 18:23:24:

I'll start this off then ! Can you take the end of the silencer to clean the inside out or is it pressed in ? Ps Thanks for the advise earlier and I'll post a picture of the engines after I've finished cleaning I forgot the worst bits the silencers crook

Trebor,

When I asked Neil Tidy how to clean a Laser silencer, he said to put a 3/8" drill down the tail pipe and drill out the crud.

Andy.

this will mostly work but you end up drilling through the baffle as well so you end up with more noise. the best bet is to never let it get all grotty in the first place by not using any castor

Frank Skilbeck24/12/2019 13:22:01
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4729 forum posts
101 photos

Just putting a Laser 62 I acquired in a Majestic Major, not done much running but bearings were gummed up and have been replaced.

While rummaging through my prop drawer I came across an 15 x 4 prop, worth a try or too much for a 62?

Andy Stephenson26/12/2019 22:20:32
169 forum posts
28 photos

this will mostly work but you end up drilling through the baffle as well so you end up with more noise. the best bet is to never let it get all grotty in the first place by not using any castor

Jon,

Neil was not suggesting that the drill went any further in than would ream out the coke in the tail pipe, certainly not through any metal inside the silencer.

This was a while ago before he changed to recommending synthetic fuels, although the some still have a small proportion of castor and create carbon deposits.

Andy.

Jon - Laser Engines27/12/2019 12:55:12
5501 forum posts
268 photos

Frank, give the 15x4 a shot. On a model like that it should work well

Andy, 3/8 will wipe out the baffle on both sizes of exhaust. Our exhaust is designed with two gas paths and carbon always blocks the one hidden from view within the exhaust. As a consequence you need to make the remaining path bigger to prevent back pressure increase by drilling through the baffle and this is what Neil always used to recommend.

Its not really a problem now with synthetic oil but in the days of 20% castor an exhaust might only last a year to two before it was blocked.

Andy Stephenson27/12/2019 17:37:22
169 forum posts
28 photos

Jon,

This was on a 150 and I only reamed the deposits by hand and no metal was removed as a result of my taking this advice. I also I believe this was only a partial solution but the best that could be achieved mechanically.

Andy.

Jon - Laser Engines27/12/2019 18:42:23
5501 forum posts
268 photos

That's fair enough but the intention behind the recommendation was always to drill through the baffle. Its the only way short of replacement to restore the exit area of the exhaust after the internal passages are blocked but it is only a bodge job solution. Once the exhaust is blocked to the degree that any of this becomes relevant its better to just buy a replacement exhaust and be done with it. In the days of 20% castor this meant a new exhaust every few years and people used to complain they needed an exhaust so frequently. Drilling though it was a free bodge that was well received as it saved the 20 quid for a new exhaust.

Unfortunately its now fallen into folk lore as a viable engineering solution when in reality its nothing more than a bandage on a broken leg.

Unless you have a 75 or other unsupported engine its better to just buy a new exhaust and use synthetic oil in your fuel. If you do that the exhaust will never need replacement unless it either falls off or is damaged in a crash.

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