MDS F2A 2.5cc
06-06-2015, 05:15 AM
#77
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Good question - based on the speed trainer write up, somewhere around 5.5 x 5, 5.5 x 6 or so.
- Propeller. The best speed was achieved with a Master Airscrew 7x5 S-2 G/F Nylon Gray Propeller cut to 140 mm (5.5 inches) diameter. With this prop the engine was turning about 30,000 rpm in the air. I suggest starting with 6 inch diameter and cutting the prop until the engine pipes up. Too small propeller will turn a lot of rpm with no thrust. We also tried more pitch (up to 6.5 inches) but this did not result in faster speed.
06-06-2015, 06:00 AM
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Hi MJD,
Glad you are having fun!
As a side note, my friend Frank, who I got the engine from, has spilt the beans...
The day we tried to run that engine... How many years ago?
Was on a 'Shoppers Drug Mart' methanol and 'gummed' Castor oil mixture !
Keep us posted...
This is a really cool thread, with lots of Worldwide information...
Cheers,
Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team
Glad you are having fun!
As a side note, my friend Frank, who I got the engine from, has spilt the beans...
The day we tried to run that engine... How many years ago?
Was on a 'Shoppers Drug Mart' methanol and 'gummed' Castor oil mixture !
Keep us posted...
This is a really cool thread, with lots of Worldwide information...
Cheers,
Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team
06-06-2015, 07:19 AM
#79
Good question - based on the speed trainer write up, somewhere around 5.5 x 5, 5.5 x 6 or so.
- Propeller. The best speed was achieved with a Master Airscrew 7x5 S-2 G/F Nylon Gray Propeller cut to 140 mm (5.5 inches) diameter. With this prop the engine was turning about 30,000 rpm in the air. I suggest starting with 6 inch diameter and cutting the prop until the engine pipes up. Too small propeller will turn a lot of rpm with no thrust. We also tried more pitch (up to 6.5 inches) but this did not result in faster speed.
IIRC, one of these two props had chunky blades that resisted breakage [but your piped engine might not like as much].
I'd test them on the ground with a big fan to force air at the engine. Hose down the area to keep the engine from sucking in dust, too.
Some of the Eliminator props listed in this size range did not have enough meat at the hub to mount to a .15, so beware.
06-07-2015, 06:54 PM
#80
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The Graupner speed 6x5.5. cut down is one possibility. I have a 5" dia version I'll try on the stand. I used that prop for setting up the pipe on the OPS .15, worked out perfectly in the air on the full 6x5.5.
Annoying the neighbours at 8:00 this evening: https://youtu.be/KqhHc34eySM
This heavy stand doesn't move on a rough surface, but these are Al bleachers, need a clamp..
Annoying the neighbours at 8:00 this evening: https://youtu.be/KqhHc34eySM
This heavy stand doesn't move on a rough surface, but these are Al bleachers, need a clamp..
06-07-2015, 10:40 PM
#82
Yes, that is a symptom of low compression.
At some point the actual flight prop has to be bolted to the engine and fired up. This is what the compression needs to be set for.
The "bench prop" is just to get a few minutes of heat controlled parts conditioning. If the engine feels good, it's time to tune for the flight prop now. Whatever size prop is considered small for a .15 speed engine. I think a 6 x 4 that's rated for the rpm would be a safe bet to launch a small delta for the first flights.
At some point the actual flight prop has to be bolted to the engine and fired up. This is what the compression needs to be set for.
The "bench prop" is just to get a few minutes of heat controlled parts conditioning. If the engine feels good, it's time to tune for the flight prop now. Whatever size prop is considered small for a .15 speed engine. I think a 6 x 4 that's rated for the rpm would be a safe bet to launch a small delta for the first flights.
Last edited by combatpigg; 06-07-2015 at 10:56 PM.
06-07-2015, 11:35 PM
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Hi MJD,
Put a pair of servos and elevons on the test stand... and I'll hand launch it for you !
I am pretty sure that engine came with extra head shims, and we put them in.
Thicker than beer can aluminum...
The Russian/English instuctions were confusing and hillarious at the same time!
I figured it was built for 10 second FF runs. ?
Seems to like the bigger pipe volume...
The SWAT team would be here within minutes, if I dared to bark that puppy, here in the GTA !
(GTA=GrosserTorontoArea)
Thanks for making beer come out my nose Mike!
Cheers,
Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team
Put a pair of servos and elevons on the test stand... and I'll hand launch it for you !
I am pretty sure that engine came with extra head shims, and we put them in.
Thicker than beer can aluminum...
The Russian/English instuctions were confusing and hillarious at the same time!
I figured it was built for 10 second FF runs. ?
Seems to like the bigger pipe volume...
The SWAT team would be here within minutes, if I dared to bark that puppy, here in the GTA !
(GTA=GrosserTorontoArea)
Thanks for making beer come out my nose Mike!
Cheers,
Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team
06-08-2015, 05:02 AM
#85
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That's about what it read when I decided to kill it. It wasn't completely at peak, you could hear it clean up and surge a little when I pulled the line.
Yep - a combat 6-4 GF prop would be a good start, pretty much what I had in mind. From there start reducing diameter and adding pitch - the 5.25 - 5.5 x 5 area sounds about right.
Dave - yeah, there are shims there. I dropped in the Profi head button designed for AMA speed (10%) and the deck clearance looked about right with one of them pulled so that's where I started. Seems there is a bit too much volume yet.
Yep - a combat 6-4 GF prop would be a good start, pretty much what I had in mind. From there start reducing diameter and adding pitch - the 5.25 - 5.5 x 5 area sounds about right.
Dave - yeah, there are shims there. I dropped in the Profi head button designed for AMA speed (10%) and the deck clearance looked about right with one of them pulled so that's where I started. Seems there is a bit too much volume yet.
06-08-2015, 12:48 PM
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Since that F2D guy is nearby in Toronto, should be no problem snagging some FG combat props locally to try out. I need to place an online order with APC sometime, low on pylon props and whatnot, so I should look at some of the APC props that might be of use. I'd like to end up on a 5" or 5.5" prop running in the 30's for the cool factor.
06-08-2015, 03:50 PM
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They have nice thin blades, perfect for this type of engine. I wonder if this thing has much more, or any more, moxie than a contemporary F2D engine. Whatever.. it has a pipe on it and it sounds great.
06-08-2015, 04:00 PM
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They have nice thin blades, perfect for this type of engine. I wonder if this thing has much more, or any more, moxie than a contemporary F2D engine. Whatever.. it has a pipe on it and it sounds great.
I think those APC props would drag it down way too much, doubt it would stage. It homed in on about 27,600 - 28,000 on the old skinny MDS pipe with a huge stinger outlet, and feels like it really wants to run 30+ now.
Might be smart just to whip up a small hershey bar shoulder wing sport speed model with side mounted engine, rather than a delta. In other words, a 26-28" span version of the Profilactic with the fuselage wrapped around a Jett 4oz tank.
I think those APC props would drag it down way too much, doubt it would stage. It homed in on about 27,600 - 28,000 on the old skinny MDS pipe with a huge stinger outlet, and feels like it really wants to run 30+ now.
Might be smart just to whip up a small hershey bar shoulder wing sport speed model with side mounted engine, rather than a delta. In other words, a 26-28" span version of the Profilactic with the fuselage wrapped around a Jett 4oz tank.
06-08-2015, 05:59 PM
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The 26" Demon already exists, but it is more than enough airplane for a .15, it was a floater with the .21 case overweight OPS .15. I'd go to 23-24 for this,but needs a center bay fuselage deep enough to bury a Jett 4 oz tank.
06-09-2015, 03:29 PM
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Funny, thinking alike are we? I was laying out 3 and 2 ounce Hayes tanks the other day, considering a rear 2oz and forward 3oz in the Mini Contender I'm converting to .15 power. The 3oz drops nicely into the forward compartment, and the 2 could sit on the radio shelf behind. But I think I'll stick to 3oz.
A pair of 2's would make a nice slim fuel compartment for the MDS.
A pair of 2's would make a nice slim fuel compartment for the MDS.
