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Laser Engines - Technical questions

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Ron Gray11/03/2019 10:59:16
1407 forum posts
358 photos

Tim, Mick Reeves sells flexi tube with pipe to fit the Laser exhaust port, about a tenner I think.

Tim Flyer11/03/2019 11:04:11
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962 forum posts
158 photos

Cheers Ron... luckily I have the stainless already . One of my club colleagues is an industrial catering engineer. It’s lovely stainless pipe. I did buy some of Mick’s pipe and brass that he sells, for my 180 (that’s a bigger outlet)in the Hurricane. This time I’m making it up myself . I fancy s bit of brazing plus this tube was given some time ago is the perfect size and want to use it . The outlet size of the 70 is smaller but my 7/16” (11.1mm) spare brass pipe seems to fit snugly 😊

Edited By Tim Flyer on 11/03/2019 11:07:58

Edited By Tim Flyer on 11/03/2019 11:08:30

Edited By Tim Flyer on 11/03/2019 11:09:49

Edited By Tim Flyer on 11/03/2019 11:10:38

Jon - Laser Engines11/03/2019 11:35:46
4570 forum posts
168 photos
Posted by Chris Walby on 08/03/2019 17:24:33:

Jon,

Do you have a recommendation regards the method for starting Laser engines?

Electric starter, chicken stick or by hand and does engine size make any difference?

... you can tell the weather is rubbish wink

I missed this one somehow, sorry about that.

Anyway i tend to electric start most of my engines as they are buried in cowlings and its a faff to try and prime them ready for a hand start. Engines that i can get to for priming get hand started unless its really cold, then i just go for gold with the electric!

Jon - Laser Engines11/03/2019 11:39:31
4570 forum posts
168 photos

Tim, if you need an O ring i can supply them. If not then your method should work for a while. The worst that will happen is it will blow goop everywhere.

Tim Flyer11/03/2019 12:08:19
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962 forum posts
158 photos

Cheers Jon I might just try the simple sleeve first with a dab of high temp silicone as the 11.1mm brass pipe is quite a nice fit

tigerman01/04/2019 17:26:48
159 forum posts

I am sure I am right but best make sure before I buy .I have a Laser 80 and want to buy the Seagull Junker CL1 ( the first World War monoplane ) If Jon is out there could you just put my mind at rest .I am sure the Laser 80 will fly this model OK .I think ?

Edited By tigerman on 01/04/2019 17:27:55

Jon - Laser Engines01/04/2019 22:15:18
4570 forum posts
168 photos
Posted by tigerman on 01/04/2019 17:26:48:

I am sure I am right but best make sure before I buy .I have a Laser 80 and want to buy the Seagull Junker CL1 ( the first World War monoplane ) If Jon is out there could you just put my mind at rest .I am sure the Laser 80 will fly this model OK .I think ?

Edited By tigerman on 01/04/2019 17:27:55

Yup, the 80 will walk it. use a 15x6 prop and all will be well.

I just looked at the specs again and the 80 will give the model more or less unlimited sport aerobatic performance. Looks like a great model though and from the instructions it looks dead easy to mod for the lower tank position should you mount the engine inverted. 

Edited By Jon - Laser Engines on 01/04/2019 22:18:29

Don Fry03/04/2019 16:48:28
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3454 forum posts
40 photos

There was a discussion somewhere about acccurately drilling holes in engine mounts. Jon said he glued engine to mount, and then did the pilot holes. Barbarian system I thought. I have just tried this technique in a vey tight, fussy installation. It works and is totally stress free. Thank you Jon.

Ron Gray03/04/2019 18:02:09
1407 forum posts
358 photos

Yep, hot glue works good!

Jon - Laser Engines03/04/2019 18:48:31
4570 forum posts
168 photos

No worries Don. I use a small drop of cyano on mine as it isnt great at sticking to glass/nylon or aluminium. its also super convenient as a have a tube of the pound land stuff on hot standby at all times!

Frank Skilbeck11/05/2019 20:51:00
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4358 forum posts
101 photos

Can anybody confirm what the carb/exhaust retaining grub screws are on a 1980s 75?

Thanks

Jon - Laser Engines11/05/2019 20:52:31
4570 forum posts
168 photos

4ba

will -017/05/2019 20:34:41
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512 forum posts
17 photos

Hi Jon, what material do you use for the o-rings on Lasers?

Jon - Laser Engines18/05/2019 00:04:55
4570 forum posts
168 photos

NBR70 for pushrod tubes and rockers, Viton for exhaust and carb

will -018/05/2019 07:45:58
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512 forum posts
17 photos

ok, I'm surprised viton works with the nitro and methanol, that's all

will -018/05/2019 07:46:00
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512 forum posts
17 photos

ok, I'm surprised viton works with the nitro and methanol, that's all

will -018/05/2019 07:46:02
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512 forum posts
17 photos

ok, I'm surprised viton works with the nitro and methanol, that's all

Frank Skilbeck18/05/2019 08:01:53
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4358 forum posts
101 photos

"A trademark of DuPont, Viton fluoroelastomer in general has a high temperature tolerance and chemical resistance rating. It is a synthetic rubber that resists many hydrocarbons, biodiesel, and petro chemicals, but is NOT compatible with ketones. Do not use Viton with acetone, esters, amines, organic acids, acetic acid, MEK, ethyl acetate, highly polar chemicals, etc."

 

We use it widely in oil and gas applications, but don't use it with titanium the flourides cause stress cracks in titanium.

BTW the seals in my 1980s 61 and 75 are still the originals................

Edited By Frank Skilbeck on 18/05/2019 08:03:36

will -018/05/2019 08:26:13
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512 forum posts
17 photos

I should explain,

all the compatibility charts i've ever looked at show "do not use" for viton for methanol and nitromethane. I appreciate you need something that will do the temperature, but I'm surprised that viton lasts in this application. If it does that's interesting, i guess the levels of exposure in the fuel/air mixture are low enough to be OK.

Jon - Laser Engines18/05/2019 09:31:53
4570 forum posts
168 photos

The viton O rings are used to seal the carb and exhaust stubs to the cylinder head so fuel never actually flows over them. Abrasion damage from the bead blasted aluminium finish is the primary cause of O ring failure we see which is why the instructions say to oil/grease the rings before fitting the exhaust on a new engine, or a replacement exhaust on an old one. This prevents damage during fitting and gives a small amount of lubrication to smooth the small movements seen in normal operation. More often than not the O rings last a good long while and there are 1990's era engines still using their original rings. I suspect they might be a bit hard by now but that is another issue all together

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