I understand that these turbines share similar or the same internals. So what is the difference between these 2 turbines????? Rabbit claims 19 pounds thrust and Merlin claims 20 pounds. Rabbit is max rpm 152k and Merlin is 160k rpm.

Apart from slignt appearance difference is there any difference at all???????

I am mainly getting at claimed thrust here in this discussion!

Mav[8D]

MERLIN SPECS from the Jets Munt website:
Specifications:

Nominal thrust: 95N (21lb) at 152.000 RPM

Idle thrust: 4.6N (<1lb)

Idle RPM: 40,000

Diameter: 90mm (3.5�)

Engine weight: 1010g (2.2lb) (including mounting strap)

Installed weight: 1,200g (3lb) including ecu, pump, valves.

Fuel: Kerosene + 3% - 5% oil (synthetic 2T motorcycle oil or turbine oil).

Pressure ratio: 3.1 to 1

EGT max: 620ºC

Massflow: 180g/sec

Fuel comsumption: 350ml/min at 95N (11,5oz/min at 21lb)

200ml/min at 60N (6,6oz/min at 13,1lb)

Rabbit specs from the Jet Central website:
SPECIFICATIONS

Thrust 8.55 Kg (19Lbs) @ 152,000 RPM
Idle Thrust: 0.36 Kg (0.8 Lbs)
RPM 40,000 - 152,000 RPM
Weigth 1.0 Kg (2.2 Lbs), with starter
Diameter 91 mm (3,582 inches)
Length 245 mm (9.645 inches), with starter
Exhaust Temperature 500°C -700°C (932°F - 1292°F)
Fuel: Jet A1, 1-K kerosene
Fuel Consumption: 0.21 Lt/min (7oz/min) Avarage
Lubrication: 2.5% Turbine Oil mixed in the fuel
Maintenance Interval: 25 hours

Chris

What on earth is an 'average' fuel consumption as stated on the Rabbit's specs?

Hi

To my knowledge there is a joint venture between these 2 companies. I own a Merlin 90 that i'll fire it up this weekend.

From the turbine wheel, you can clearly see that the casting is Jets-Munt. I believe the internals should share many mechanical components.

The specs are pretty much the same. Also the cables from the Merlin starter motor come from the inside along with the rpm sensor and in the Rabbit come from the motor.

Electronics are both made by Gaspar Espiell from jets Munt.

There is a test in this month RCJI and I am very confident that this is a great turbine and that I won't regret the fact that I changed it by a P60 in the F16. All in all you can get 95N thrust from a 1Kg weight turbine. That's impressive....

I'll let you know more details when I ran it.

I just regret the fact that the rpm and temp cables are integrated in the turbine and don't have an external cable. That way if you need to take it out of the plane you have to unroot these cables from the frame

Either one you'll choose you'll be ok

Regards

Nuno

We flew our Merlin 90 yesterday for the first time. It is such a light engine and is so physically small that it is a great choice if you want to change from a smaller engine to get more power. I had a Super Bee in the Swallow and the engine rails needed very little modification. The Merlin is actually shorter. It has very fast accelertion and was surprisingly economical. Loads of power of course and low temperatures. If anyone is buying one and needs a fod screen I used a P60 screen and the temps were fine. This is a very fine engine.

John

My point here is if the engines are basically identical and share similar internals, why does the Merlin quote 21 pounds thrust at 152k rpm and the rabbit 19 pounds of thrust at 152k rpm.

Is this just manufacturer "marketing" talking up their specs, that are difficult to confirm nor deny???

Mav[8D]

I have a Rabbit in my 23# Gripen. I suspect the 19# spec from JetCentral is conservative. It feels like more than 19. But who knows....

The Rabbit noise itself is pretty amazing. This is hard to describe.

Arnaud

Is anyone in the US flying a Merlin 90?
Jim

We don't lie with specifications nor publish performance figures at -20ºC... Not difficult at all to confirm, just purchase the last issue of RCJI magazine, where the M90 is reviewed, you will see the data collected by Tom Wilkinson during his tests on test bench.

Gaspar

What is Merlin's warranty like? Turn around time for service?

where can you by it ??

Dreamworks sells them: http://www.dreamworksrc.com/catalog/...hp?cPath=62_93
Jim

Gaspar,

Ihave 160mk11 & 90 - both haul arse,

Merlin all the way .

Burn baby , burn.

you fly jets ? and you don't know what average fuel consumpsion is ?

That's sad.

Currently is two years, but probably will expand this time soon. Turnaround depends on transit time, but on M90s they stay here for less than a week.

GAspar

OK Scoeroo, can you tell me how Jet Central calculate their 'average fuel consumption'? What power settings they use for their test and for how long?

In my opinion, average consumption is very misleading because it depends on the model weight. Also, since all manufacturers define turbine by their max thrust, they should also provide consumption at maximum thrust. Otherwise, it is impossible to compare 2 turbines.

Arnaud

Well gentlemen, here again are the much debated words "average fuel consumpton." This subject if you research it has been sliced, diced, sauteed, blended. . .well, you get the point.

We at Jet Central use the term "average fuel consumption" when quoting figures for each turbine we sell. This figure is based upon flying each turbine for a specific amount of time (normally 8 minutes) draining the fuel, measuring the amount left, subtract from total fuel load - less UAT then divide to determine average fuel consumption. This in our opinion is what customers really want to know. Jet pilots all do the same thing. . .start, taxi, take off, fly and then land. Few and I do mean few go to WOT at take off and stay there until time to land. When a customer calls and requests specifics on a turbine, fuel consumption always comes up. Let's look at my BobCat composite with all three tanks.
With Rabbit installed and all tanks full, I can fly 8 minutes, land, taxi back and still have fuel left over. Hence, an easy 7 oz per minute. Our latest jet, the FEJ 1/7 F-15 has our Rhino installed. This jet carries 240 oz. however, we limit ourselves to 185 oz. Take off, fly for 7 minutes and land. We still have remaining fuel in the two saddle tanks and the main has not been touched. Hence, this calculates to 17 oz. per minute. Is this not what just about every flier wants to know?

Full throttle fuel consumption is an almost meaningless figure because we do not fly this way.

For the interested, our average fuel consumption based upon our testing for each turbine is listed below:

jf50 Super Bee - - 6oz. per minute
VT 90 Rabbit - - 7oz. per minute
jf100 Falcon - - 10 oz per minute
jf120 Super Eagle - 14 oz per minute
jf170 Rhino - - 17oz per minute

jf50 TP turbo prop 7 oz per minute

Each of the above have been tested in compatible jet models with supplied manufacturers fuel tanks and the turbine the manufacturer recommends with his particular jet. We fly the TP in the Comp-ARF Tucano. . .near 48 lbs at take off yet, we do not stay at WOT unless going into a vertical maneuver or the often presented "high speed pass."

This question/issue can and probably will go on for ever, but we are very satisfied with the way we provide our fuel consumption figures.

Best regards,
Eric Clapp

Not me. I want to know how it compares with other engines. I agree full throttle fuel consumption is only part of it but your 'average' consumption is also meaningless to me for 2 reasons. Firstly, all it tells me is how much fuel you average in your installation and your style of flying. Secondly, I can't tell from your figures whether it is better or worse than any other engine.

A case in point, of the 2 engines above, which has the better fuel consumption and how can you tell from the specs?

sicklick:

In answer to your question(s) if you are basing fuel consumption as the primary question when deciding which turbine to purchase, I think it safe to say you are putting aside quite valuable additional information.

For your question of which of the "above" gets better fuel consumption, an answer would not be valid based upon data provided. However, if the M-90 were run at the same max RPM our Rabbit is set to, the fuel consumption for each turbine would be near identical.

There is far more to consider when deciding on turbine A or turbine B than fuel consumption. Again, we all fly basically the same way. If turbine A uses 12oz per minute WOT and turbine B uses 11oz per minute, but you realize after flying, your consumption was actually 7oz per minute based upon your flying style. . . .which would be factored into the time you set on your Tx ?

Best regards,
Eric Clapp

That's it for posting today. . .We are off to watch the Air Show in Punta Gorda, Florida. Blues go off at 3PM. Speaking of the Blues, their fuel load is based upon each particular jets mission in the formation plus reserve for an alternate. . .this from a good friend who was a former team member.

Hi Darren, check out my Bobcat/M90 and Rookie/Super Eagle at Shawbury next Sunday or the next Elvington meet, fuel figures are pretty similar to those quoted.

Regards

Rob.

Gaspar,

Can Merlins be serviced in the USA or do they need to be sent to Spain for service?

Joe

Eric,

As much as I'm a fan of your products and service, I have to disagree on this point. The average throttle position varies greatly from one model to another. Some models are heavier. Some models have a lot more drag. As a result, some will fly mostly at 60%, 50% or 90-100% gas. For example, I fly my Elan with an average of 60% gas but fly my bandit, which is a little underpowered at 100% all day long.

Sometimes I decide to slightly underpower a model because I want to save on weight. This is for example why I have a Rabbit in my SM gripen. I prefer to evaluate fuel consumption by starting at the full thrust value and evaluate what will be the average throttle position depending on how over powered or under powered the model is.

Arnaud

Joe, FYI, I inquired to Todd at Dreamworks last summer (since he sells them) about service. He indicated to me that he would be doing service in the US.
Jim

Average is about the best way of estimating.
You should care less about WOT settings unless that is the only way you fly, but then in that case you need a different turbine as it is powered incorrectly.

It is possible turbine A burns more at 100% RPM than turbine B but then turbine A burns less at 90% thrust than turbine B so how are you going to figure out what you need to know unless you have massive manuals of horrific looking charts.....oh yeah maybe you work for the FAA legal department.

If you are so concerned about fuel you should be asking for fuel charts for burn/thrust rates at every 1000 RPM, every temperature at those RPMs and lest we forget about every altitude at every RPM and every temperature...oh and then add in each possibility of humidity with each RPM, temperature, altitude etc...oh wait then what the difference in all those would be with Jet A versus Kerosene and then we could go on with each of those with each type of turbine oil...percentages of oil and then maybe even some numbers for 2 cycle oil.

forgot another one ...with and wihtout anti- static magic elixir for the purple ones.

For how much effort that would be on the part of the manufacturers and then add in the constant upgrades to service you can see it would be totally cost prohibitive in time and funds to produce such charts.

Asking for more is just being anal. Buy what is reliable, easy to get repaired if needed and makes you happy.

If you don't like the way the numbers are provided, buy the ones you are deciding on and then sell the ones you don't like....other than doing that you will never be happy.


BC