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Laser Engines - Technical questions

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Manish Chandrayan11/02/2019 18:02:52
560 forum posts
65 photos
It's stamped with my initials and J 11.
So it's either Jan/June/July 2011.
2.5mm key does not fit in the screw head but a 5/64 does
Martin Harris11/02/2019 18:19:48
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8481 forum posts
212 photos

If its that new you can safely ignore my previous suggestion. Doesn't a 2mm key fit - it's only very slightly larger than 5/32 - which is over 1.984mm

Jon - Laser Engines12/02/2019 08:31:52
4597 forum posts
172 photos

My bad. Standard M3 cap heads need a 2.5mm key but the button head rocker cover screws are 2mm.

 

And J 11 means it was built by me in 2011. We dont record months. 

Edited By Jon - Laser Engines on 12/02/2019 08:32:36

Manish Chandrayan12/02/2019 11:30:08
560 forum posts
65 photos

Thanks everyone for chipping in.

Yes the 5/64 and 2mm keys both engage the original screws on the rocker cover. The threads were checked with an existing known M3 screw and nut. Once confirmed both the screws on the rocker cover were replace with standard cap head M3 screws that I had (that required 2.5mm keys) instead of the domed/button head original screws. Couldn't have one cap head and other domed wink 2

The engine is old in years (purchased when I started the model) but has not run more than 2 full tanks (12 Oz). During these runs, all I could get was 7500-7600 peak using a 16x8 Graupner on home brew 5% Nitro, 16% Oil fuel. Since the rocker covers were off, checked the gaps and found them to be much more than 0.1mm. Using the same gauge I reset the gaps to tight fit on 0.1mm. Hope to run the engine again coming weekend and see the top end climb up some

Jon - Laser Engines12/02/2019 12:44:16
4597 forum posts
172 photos

I would expect 8000-8500 on 16x8 props, depending on engine age/spec and the type of prop. Also if you have a decent oil you can come down to 10 or 12% oil with no bother.

Manish Chandrayan12/02/2019 13:27:44
560 forum posts
65 photos

Yes, Jon you had said that earlier about the expected RPM's. And that's the reason why I was not happy about the 7500 I was seeing.

I expect around 8000-8250 given the high temp and humidity levels we experience locally. As for oil, it's Klotz and since it is going to run on a scale Tiger Moth (cowled with scale intake and baffle) I would stick with 16% oil. And that's my standard brew for all four strokes I run.

Jon - Laser Engines12/02/2019 13:31:22
4597 forum posts
172 photos
Posted by Manish Chandrayan on 12/02/2019 13:27:44:

As for oil, it's Klotz and since it is going to run on a scale Tiger Moth (cowled with scale intake and baffle) I would stick with 16% oil.

Why does the model influence the lubrication requirement of the engine?

For a tiger you can use 17x6 or 18x6

Tim Flyer12/02/2019 13:39:58
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966 forum posts
160 photos

I would think he would need Esso oil for this plane as they always said “put a tiger in your tank” 😉

Manish Chandrayan12/02/2019 13:48:03
560 forum posts
65 photos
Posted by Jon - Laser Engines on 12/02/2019 13:31:22:
Posted by Manish Chandrayan on 12/02/2019 13:27:44:

As for oil, it's Klotz and since it is going to run on a scale Tiger Moth (cowled with scale intake and baffle) I would stick with 16% oil.

Why does the model influence the lubrication requirement of the engine?

For a tiger you can use 17x6 or 18x6

Because the engine rotates in the opposite direction wink 2

Manish Chandrayan12/02/2019 13:50:03
560 forum posts
65 photos
Posted by Tim Flyer on 12/02/2019 13:39:58:

I would think he would need Esso oil for this plane as they always said “put a tiger in your tank” 😉

Will see if I can get hold of a Tiger. Not many left I guess wink 2

Jon - Laser Engines12/02/2019 14:04:00
4597 forum posts
172 photos
Posted by Manish Chandrayan on 12/02/2019 13:48:03:
Posted by Jon - Laser Engines on 12/02/2019 13:31:22:
Posted by Manish Chandrayan on 12/02/2019 13:27:44:

As for oil, it's Klotz and since it is going to run on a scale Tiger Moth (cowled with scale intake and baffle) I would stick with 16% oil.

Why does the model influence the lubrication requirement of the engine?

For a tiger you can use 17x6 or 18x6

Because the engine rotates in the opposite direction wink 2

The engine does not care which way it rotates. Did you re time it to run backwards? if so that could be why its slow

Manish Chandrayan12/02/2019 14:21:22
560 forum posts
65 photos

Will try and post the results as long as you promise to service the engine free of cost

Ok! Ok! I will cover one way shippingsmiley

Jon - Laser Engines12/02/2019 14:32:12
4597 forum posts
172 photos
Posted by Manish Chandrayan on 12/02/2019 14:21:22:

Will try and post the results as long as you promise to service the engine free of cost

Ok! Ok! I will cover one way shippingsmiley

Im not quite sure i follow. Why am i giving away free services? dont know

Manish Chandrayan16/02/2019 14:18:42
560 forum posts
65 photos
Happy to report that with the gaps reset ran the engine today on bench.
Temp were around 32 degree Celsius. Fuel was my standard brew 5% nitro, 16% Klotz. Prop Graupner grey 16x8. Tach read 8300 steady and confirmed with two different tachs. Engine was run for half tank, then shut down allowed to cool down for quite some time (continued flying other models)
Same fuel and set up and prop changed to 16x8 APC. Needles untouched. Reading straight way showed around 8520. Engine was allowed to run and it drained the tank dry.
The Tiger will be maidened using the APC. Will use the 17 or 18 props once the engine has accumulated some run time.

Edited By Manish Chandrayan on 16/02/2019 14:19:48

Jon - Laser Engines16/02/2019 15:48:43
4597 forum posts
172 photos

8500 is good for an apc 16x8 and what they always used to do. I do think they have changed them though as i cant get any of my new 16x8s to run faster than 8200 even on 155's. I cant understand why they would change the design of the prop but even engines i know used to run that fast on 16x8's now run 500 revs slower, even though the run at expected revs on other props. Most strange. APC what did you do?!

Martin Harris16/02/2019 17:59:29
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8481 forum posts
212 photos

It does seem odd Jon. New moulds would represent a large investment. Could your fuel have changed? Have you tried an old APC?

Scott Edwards 216/02/2019 18:00:01
173 forum posts
93 photos

Oh my word! It's not just me then! I would get about 8300 on a very old 150 with an APC 16*8. Roll on 20 years, and I get about 8100 on a 155 on a new prop in the same model. But -There's definitely more performance. Maybe APC have subtley changed design with greater efficiency but also greater inertia?

Bruce Collinson18/02/2019 11:14:04
346 forum posts

Is it considered appropriate to ask a technical question about Lasers here without gratuitous sideswipes concerning production levels?

I'll assume it is. Jon knows I have a tank height issue with a Probuild Infinity and a Laser 100 which I may have solved by moulding a Sullivan Flex tank and installing it below the u/c plate. It ran a treat when first fired up last Sat, upright, inverted and vertical (sorry Jon, they made me do that). Hoping to maiden very soon. The tank and lower cowl are still falling out with each other and the tank will need further moulding before it flies with the cowl fitted.

Question, prompted by a clubmate; is there any reason not to fabricate an intake manifold extension to raise the spraybar height about an inch and move the tank to the top of the u/c plate? Said clubmate has a similar arrangement on an OS, milled from solid aluminium.

Thoughts? Might not be worth the faffing ...

BTC

Paul james 818/02/2019 11:36:03
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126 forum posts
23 photos

Interesting idea Bruce, can't see why it wouldn't work, probably best not to have too abrupt a bend leading into the inlet port as it may cause turbulence but might not make much difference. Most other 4 strokes seem to have the carb much "lower" with an inlet stub having quite a sharp bend where it meets the head.

I've made up different exhausts to fit them and inlet stubs with different carburetors, all of which have worked fine.

It seems to be the height of the carburetor centreline relative to the fuel tank that is important on these and how they are as standard isn't always the easiest to accommodate in a model. That is an observation rather than a criticism.

Let us know how you get on

 

Edited By Paul james 8 on 18/02/2019 11:36:34

Jon - Laser Engines18/02/2019 12:08:39
4597 forum posts
172 photos

We have been asked before about offering an os/saito/every other 4 stroke style intake manifold and the thought process is as follows.

Yes it will work, the engine will run, its not going to damage it.

However, As we tested it years ago we know that throttle response, idle performance, reliability and flooding will all be negatively impacted by the change.

All engines come with certain requirements for their operation and tank-carb height is one of them for all non pumped engines. in our case this means lowering the fuel tank. This also applies to the OS flat 4 and OS/ASP flat twins as well.

The choice then is with the customer. Make the required changes to the model and enjoy the optimised performance on offer from our direct intake, leave the model and as is and have problems running the engine without modification, or leave the model as it is and tolerate less than perfect performance from a modified engine. I know which one i would choose and to date i have not found a model that was impossible to modify to suit the tank position required by the engine. That said, if everyone says they are happy with reduced performance in the interest of not having to modify stuff then i would say you were crazy but would see what i could do to help

I work on the basis that its only wood and my many tools will make short work of that

 

Edited By Jon - Laser Engines on 18/02/2019 12:09:44

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