Laser Engines - Technical questions

[Cuban8]

Could you explain how the chicken hopper systrm works please? I did Google it and found a control line forum where there was some debate over the terms 'chicken hopper' and 'vacuum break system' and what's actually used in fuel systems.

Edited By Pete B - Moderator on 18/12/2017 09:15:57

[Rocker]

Thanks .As I said I have no problem with the Wots Wot XL because I will fit it at right angles as this is not a scale model I.m not bothered about the engine sticking out of the cowling.It just that my end goal is a big warbird ,so the main reason for buying the 180 will be to fit in to a big warbird but has I have never had a big model before and this will be my first big model I thought it would be better to start with Wots Wot Xl to see how I get on and then progress to the warbird. I see what you are saying that there is more room in the bigger models and I will have room to cut away a section to accommodate the tank being put in the right place .Great I think that is sorted .Now all I need is for Jon to get busy with the 180 .Hopefully after the Christmas madness is over I can start on getting the Wots Wot XL .Looking forward to that

[bert baker]

My Stampe did a massive loop at full throttle and my son forgot to reduce the power when he reached the top, It didn't like the amount of G force, -and clapped its wings, engine went in quite hard and sheared of the brass section and distroyed the spray bar

[Jon H]

Rocker I'm not sure which warbird you are looking at as a stepping stone but Tim Harris of the North London club is looking at the Seagull Hurricane with our 180 in the nose as it will need very few mods. Its likely to be quite forgiving as a model too so might make a good choice for you.

Production wise I'm close, but I'm not sure if I will make it before the deadline which is going to be Tuesday morning. I will do all I can.

Bert, yeaa that would do it!

[Ron Gray]

Posted by Jon Harper - Laser Engines on 16/12/2017 15:13:04

Production wise I'm close, but I'm not sure if I will make it before the deadline which is going to be Tuesday morning. I will do all I can.

Lightweight, you’ve got tomorrow 😉

[Steve Dunne]

Posted by Cuban8 on 16/12/2017 10:20:36:

Could you explain how the chicken hopper systrm works please? I did Google it and found a control line forum where there was some debate over the terms 'chicken hopper' and 'vacuum break system' and what's actually used in fuel systems.

Sorry for slow reply - I was just on my way out to the ice floes flying field when I saw your post. I will put a sketch together over the weekend and post it in a couple of days.

Edited By Pete B - Moderator on 18/12/2017 09:18:04

[Rocker]

The Seagull Hurricane looks good ( The Hurricane being my favorite warbird ,It looks a good first warbird)I am not to bothered about getting the Laser 180 before Christmas ,after Christmas /New Year will be just fine

[Rocker]

So would I be right in saying that all the warbirds that require a 35cc petrol engine a Laser 180 would be the four stroke equivalent and the Laser 180 would be OK to fly them ?

[Jon H]

Posted by Rocker on 16/12/2017 16:47:02:

So would I be right in saying that all the warbirds that require a 35cc petrol engine a Laser 180 would be the four stroke equivalent and the Laser 180 would be OK to fly them ?

Not exactly. Most kit recommendations should be taken with a pinch of salt as often they list engines that are too large to prevent people complaining the model is not fast enough. Equally though, some models need more power than the mfr states due to an inaccurate weight or some other issue.

My La7 for example used to fly on a 180, it was fine, but its waay better with the 300. Sure the 300 is now too much for scale, but its good fun and makes the model a great deal better.

The Hurricane is lighter, and the full size was not in the same league as something like the la7 so the 180 is likely to be just fine. I flew an 80 inch 14lb mick reeves hurricane on our 120 without any trouble so the seagull version at 16 or 17 lbs will be no problem.

[bert baker]

I agree with you John,

My 45cc Blackhorse Chippy flys very well on a G 38. And I here of plenty on DLE 30s

But one was being flown on a Laser 150

[Jon H]

Posted by bert baker on 16/12/2017 17:57:01:

I agree with you John,

My 45cc Blackhorse Chippy flys very well on a G 38. And I here of plenty on DLE 30s

But one was being flown on a Laser 150

The 45cc chippy will fly on a 120! its way over powered with a 45cc. a decent 150-180 4 stroke would be my recommendation

[Steve Dunne]

Posted by Cuban8 on 16/12/2017 10:20:36:

Could you explain how the chicken hopper systrm works please? I did Google it and found a control line forum where there was some debate over the terms 'chicken hopper' and 'vacuum break system' and what's actually used in fuel systems.

Here is a sketch of my chicken hopper tank system:

Please note: When filling the tank you must ensure that the top tank is completely full so that it starts feeding the bottom tank. Stop filling when the bottom tank starts spilling.

To empty the system, first drain the top tank, then invert the aircraft and drain the bottom tank.

The air release tube fitting is a fuel bottle fitting.

When building the system, ensure that the bottom tank spill tube end is above the bottom of the air release tube, so that the fuel level does not reach the spill tube before the air release tube is blocked by the rising fuel surface..

How does it work?

When the fuel level in the small tank falls, it allows air up the release line, which then allows fuel to come down the fill line into the small tank. When the fuel level in the small tank rises to block off the release line, a partial vacuum forms in the top tank, stopping the fuel feeding out and down the fill line.

Even the chickens can work it!

So far the system has worked very well for me, in a H9 81" Spitfire.

Steve.

Edited By Steve Dunne on 17/12/2017 20:30:36

Edited By Pete B - Moderator on 18/12/2017 09:17:05

[ChrisB]

Posted by Steve Dunne on 17/12/2017 20:29:33:

Posted by Cuban8 on 16/12/2017 10:20:36:

Could you explain how the chicken hopper systrm works please? I did Google it and found a control line forum where there was some debate over the terms 'chicken hopper' and 'vacuum break system' and what's actually used in fuel systems.

Here is a sketch of my chicken hopper tank system:

Whats the benefit of the Chicken Hopper?

CB

Edited By Pete B - Moderator on 18/12/2017 09:19:27

[Denis Watkins]

Your main tank can be accommodated easily, further back in the model where there's more space

And the slave in line with your carb, always at the right height, as its smaller, its easier to find space for it

 

Edited By Pete B - Moderator on 18/12/2017 09:19:58

[Steve Dunne]

I am able to fly the Spitfire with the main tank about 11cm above the carburetter on an inverted 180. It would not be possible to operate with a laser otherwise, as there is not physically room for a tank larger than 4oz at the bottom of the fuz.

Steve.

Edited By Pete B - Moderator on 18/12/2017 09:20:28

[Ron Gray]

I presume that it allows the ‘main’ tank to be fitted higher up without the risk of fuel pouring out of the carb.

Edited By Pete B - Moderator on 18/12/2017 09:20:53

[Tim Flyer]

 

Great Idea that Chicken hopper system . It’s also used by model power boaters to stop their massive tanks drowning the engine and gives a less bubbly fuel flow as the fuel in the small tank doesn’t slosh around so much in manoeuvres.

Re Rockers question on the 180 and the Seagull Hurricane....I think it should be quite forgiving and if it is anything like as good as Seagull ‘s excellent P47 I bought last year it should be a really fun model . I was very impressed with Seagull quality and it should be easy to add a few touches to improve the looks. I will use the HK heavy duty electric retracts again too, plus make sure they are angled forward enough to stop any annoying taxiing nose overs. Before I get it started though I have to finish my 72inch LA7 and a few other diy projects which are still waiting . Happy Flying all.

 

 

Edited By Timothy Harris 1 on 18/12/2017 10:06:32

[bert baker]

Is it possible to remove the front crank case with aid of hot air gun without removing the crank,on a 150

[Cuban8]

Many thanks for posting the diagram, very ingenious system. I've got enough old fuel tanks and tubing kicking around to cobble something up on the bench and watch it working.

[Steve Dunne]

Let me know how you get on...

Steve.

[bert baker]

I have been trying to work it out but keep going back to the top tank bent to top of bottom tank

[Steve Dunne]

Posted by bert baker on 18/12/2017 10:49:39:

I have been trying to work it out but keep going back to the top tank bent to top of bottom tank

The middle pipe in the top tank is the clunk line. When the partial vacuum in the top tank is released by the level in the bottom tank dropping below the stub pipe in the air release line, fuel syphons from the top clunk into the bottom tank. This raises the fuel level in the bottom tank until it reaches the stub pipe, which then blocks the flow of air back into the top tank, causing a partial vacuum in the top tank as the fuel flows out. Eventually the partial vacuum stops the flow of fuel from the top tank (via the clunk), and the cycle starts again.

It pretty much stays in equilibrium.

Quick note to dispell some confusion - in flight the "fill" line is blocked off, as per usual, and the "spill" line is open and facing forward, again as per usual. That allows the top tank to be a partial vacuum, and the bottom tank can breathe.

Steve.

Edited By Steve Dunne on 18/12/2017 11:33:51

[trebor]

Posted by bert baker on 18/12/2017 10:40:06:

Is it possible to remove the front crank case with aid of hot air gun without removing the crank,on a 150

You will be lucky, I wouldn't leave the crank swinging on the conrod. Maybe I've read this wrong !

[Jon H]

It's not really possible Bert unless you remove the prop driver first. Even so, I'm not sure why you would be worried about removing the crank as it's only got to engage with the pinion drive and conrod. It won't upset the cams or anything

[Bob Cotsford]

bert, why not just pull the crank with the housing? I did this when replacing the front and main bearing on my Laser. It doesn't disturb the timing as that's driven from a slotted disk that the crankpin locates into.