Go Back  RCU Forums > RC Airplanes > Extreme Speed Prop Planes
Reload this Page >

Diamond dust motor mounting 1/4" higher than spec.

Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Diamond dust motor mounting 1/4" higher than spec.

Reply

Old 09-22-2002, 08:36 PM
  #1  
Roadrunner1390
Member
Thread Starter
 
Join Date: Aug 2002
Location: Hartford, CT
Posts: 53
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Diamond dust motor mounting 1/4" higher than spec.

I am mounting a Rossi 53 ducted fan motor on a Diamond Dust.
The motor is rear exhaust and rear intake. The problem I am having is when I place the motor on the mount, the intake hits the firewall lip. I have cut out allot of the firewall and am going to re-enforce the area with hardwood and epoxy. I could not mount the engine flush with the mounting deck. I had to put 1/4" hardwood rails for the motor to sit on.

Is this going to drasticly change the flight characteristics ????
Roadrunner1390 is offline  
Reply With Quote
Old 09-22-2002, 08:56 PM
  #2  
ChuckAuger
Senior Member
My Feedback: (12)
 
Join Date: Dec 2001
Location: Pampa, TX
Posts: 5,133
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Take a look...

At the thread just below..I posted some links to some pics of how to to mount a DF engine on a DDust... If you would like, I can send you the nose piece from my departed DDust to see how I did it..it CAN be done...don't raise the engine!

http://www.rcuniverse.com/showthread...55&forumid=162

http://www.rcuniverse.com/showthread...15&forumid=162

Do a search for my user name in this forum..there have been a couple of guys tempted to raise the engine..you can get around it..here is a re-post of the best pic I have of it...

]
ChuckAuger is offline  
Reply With Quote
Old 09-22-2002, 09:49 PM
  #3  
Roadrunner1390
Member
Thread Starter
 
Join Date: Aug 2002
Location: Hartford, CT
Posts: 53
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Diamond dust motor mounting 1/4" higher than spec.

The pictures looked good. I wish I was in the building stages. This would be easy. However, I am not. How do you think it will fly with the motor 1/4" higher than normal???????
Roadrunner1390 is offline  
Reply With Quote
Old 09-25-2002, 02:28 AM
  #4  
Dave McDonald
My Feedback: (19)
 
Join Date: Jan 2002
Location: Eldon, MO
Posts: 1,856
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Higher thrustline on DD

After my plywood motor mount cracked, I sandwiched it between two pieces of 1/16" aluminum. Like you, I was also worried about raising the thrustline. But after flying the DD with the TT Pro 36 (shown), and then a piped K&B 7.5cc DF, I couldn't tell any difference at all in the way the DD felt inflight with the raised thrustline.

Therefore, I don't think that raising the engine 1/4" will make near as much difference as you think it will.....if you can even tell the difference at all.
Attached Thumbnails Click image for larger version

Name:	27556_1463.jpg
Views:	3
Size:	52.7 KB
ID:	16986  
Dave McDonald is offline  
Reply With Quote
Old 09-25-2002, 07:37 AM
  #5  
Roadrunner1390
Member
Thread Starter
 
Join Date: Aug 2002
Location: Hartford, CT
Posts: 53
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Diamond dust motor mounting 1/4" higher than spec.

Dave thanks for the reply. 1/16 is a lot less than a 1/4. I hope I have the same results.
I am hoping to fly her by saturday. I will post a thread and let everyone know how it worked out.
It would be a lot of cutting to put it flush. I can see doing it when you are building a new one, however, I went from a 46 fx (piped) to the Rossi 53 DF. I would have had to peel the thing like a banna to get the re-enforcements to my liking. Happy flying.

P.S. how fast is yours going ????

RR
Roadrunner1390 is offline  
Reply With Quote
Old 09-26-2002, 03:02 AM
  #6  
Dave McDonald
My Feedback: (19)
 
Join Date: Jan 2002
Location: Eldon, MO
Posts: 1,856
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Diamond dust motor mounting 1/4" higher than spec.

Roadrunner1390,
I agree that 1/4" is more than 1/16".......but then again it's only 3/16" more.

If you consider that the overall length of the DD wing is about 25", then raising the thrustline by 1/4" only amounts to about a 1% change relative to the chord of the wing. I would consider a 1% change to be fairly insignificant.

Other than possibly requiring a very very slight change in the amount of up elevator trim, I don't think you will notice the 1/4" raised thrustline.


P.S. how fast is yours going ????
I never had a chance to clock my DD before it went to balsa heaven, so I really don't know the answer to your question. I truly wish I did.....but I don't.....and now it's too late.
Dave McDonald is offline  
Reply With Quote
Old 09-26-2002, 03:47 AM
  #7  
Roadrunner1390
Member
Thread Starter
 
Join Date: Aug 2002
Location: Hartford, CT
Posts: 53
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Diamond dust motor mounting 1/4" higher than spec.

Dave, I have not yet flown the damn thing. I have been so busy locking up bad guys that I have not finished putting the tank and little odds and ends together. I'm close though!!

I hope by Sunday evening I will have a big smile. Or a big pile of balsa !! My last dust was pushed by a tired OS 46SF ( 11x6 prop)with a mac tuned pipe. I was just shy of 14k on the rpms and was on radar at 127 mph. I am now at a minimum of 18k and a 9x9 prop. I am told that it should be super sonic. And if I drop to an 8x9 she will be screaming !!! I cant wait to test fly it.

I have many people tell me that the 1/4 " is going to be no big deal. I hope so !! When you look at it, you hardly notice the motor up.

What motor were you running when the Dust was alive ??

dpsmith1390@attbi.com
Roadrunner1390 is offline  
Reply With Quote
Old 09-26-2002, 04:51 AM
  #8  
Dave McDonald
My Feedback: (19)
 
Join Date: Jan 2002
Location: Eldon, MO
Posts: 1,856
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Diamond dust motor mounting 1/4" higher than spec.

Roadrunner1390,
First, make sure you get all those bad guys rounded up and put away so it's safe for the rest of us to go flying!

What motor were you running when the Dust was alive ??
My DD started out with a piped K&B 7.5cc DF, with a Perry pump and carb. But I could never get the engine to run consistently with the pump, so I switched to Perry carb from an old K&B .61. This no doubt cost me a considerable amount of top end power, but at least the engine ran fairly consistently with an APC 9x7, and it was fairly fast.

I also flew that DD with an OS 32 w/MCP, Webra 32 w/MCP, OS 40FP w/MCP, Thunder Tiger 42GP w/MCP, Thunder Tiger Pro 36 w/MCP. Of these, the TT Pro 36 w/MCP was the fastest, but not as fast as the piped K&B 7.5cc DF.

When it finally crashed, I'd been flying my DD with a K&B 6.5cc with the factory pipe/muffler that resembles a mousse can. I put the Perry pumper carb on it because it has a huge diameter throat, but this time, I didn't use the troublesome Perry backplate pump. Besides, muffler pressure worked fine to feed the carb at full throttle. Best prop seemed to be the APC 8x8, but I never spent the ca$h to experiment with the expen$ive carbon fiber racing prop$. I suspect that this setup was even faster than the piped K&B 7.5cc that I started out with.

After seeing my K&B 6.5cc DD fly, a buddy of mine became fascinated with the speed and built a DD of his own, even though he had no intention of ever flying it himself. He just wanted to watch it go as fast as possible.

He ended up powering his DD with a piped Jett FIRE 50. So far, the APC 8.75x9 seems to work the best on the Jett, but I can't remember what the RPMs were. I wish I still had my DD with the K&B 6.5cc to run them side by side because his Jett 50 DD doesn't really feel any faster to me than my deceased DD with the K&B 6.5cc.

However, the Jett FIRE 50 runs perfectly on every flight....unlike the K&B 6.5cc. The Jett FIRE 50 has an excellent throttle, and throttle response......unlike my K&B 6.5cc with the Perry pumper carb. The Jett FIRE 50 has only gone through 2 or 3 glowplugs in about 100 flights.....unlike the K&B 6.5cc which ate a plug every second or third flight.

At one of our club fun flys this year, a DD pilot was there from another club. He had been flying his DD with an MVVS GRRT 40 and felt it was pretty fast. But after watching the Jett FIRE 50 DD fly just once, he stated that his DD couldn't even come close to that speed.

In the long run if you want to go fast consistently, the Jett FIRE 50 is definitely worth the extra bucks!

If you still want more details, you can check out my Diamond Dust web page at this URL:
http://mypage.yhti.net/~dmcdnld/diamonddust.htm
Dave McDonald is offline  
Reply With Quote
Old 09-26-2002, 02:19 PM
  #9  
Roadrunner1390
Member
Thread Starter
 
Join Date: Aug 2002
Location: Hartford, CT
Posts: 53
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Diamond dust motor mounting 1/4" higher than spec.

Wow, did you guys ever get a radar gun on those monsters ??
I will drive out to Mo. with mine if my Sgt. will ok it !!!

I wanted to go with the 32 size motors due to the weight of it and of the DD. However, I fell into the Rossi 53 and decided that I mostly fly planes that I can put this on if I decide that its not for the dust.

I will check out the link you posted. I will also check into the carbon fiber props. These damn storms from the gulf are going to kill the flying this weekend in New England. I dont mind them when I have wrecked all my stuff and need a weekend to build. But when I have a fire breathing DD on the bench with a big DF waiting to take it into orbit, it sucks!!!!!!

P.S. who am I kidding, I dont get anywhere close to orbit. At our field its "lower, lower" from the peanut gallery !! I have skipped mine off the runway twice at 127 mph !! Both times I just glided into the tall stuff with no damage . The record is one to beat however. Although I have scraped the ground I am not the champ. How you say ?? Well another DD pilot who we nicknamed Weenie skipped his off the ground, killed the motor on impact, then it re-started !!! Hats off, he is the king !! (second sucks) I will wreck trying to top that !! But I saw it with my own eyes, the son of a B--ch started back up. We were running OS 46's with mtp's. Thats all for now. Pray for a break so I can take the dust out for a walk...

RR
Roadrunner1390 is offline  
Reply With Quote
Old 09-30-2002, 01:11 PM
  #10  
Roadrunner1390
Member
Thread Starter
 
Join Date: Aug 2002
Location: Hartford, CT
Posts: 53
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Diamond dust motor mounting 1/4" higher than spec.

The flight of the animal

Wow this thing ripped out of the hands of the launcher like it was shot from an aircraft carrier!!

I havn't had this much fun with my cloths on in a long time !!

The resuls are in from the test flight:

Well the weather in Connecticut held off and was great for flying.
The dust got a lot of looks when I took it out of the Explorer. I got even more looks when I fired it up and it pierced everyones ears !!

As my buddy was holding the DD while I fine tuned the needle, I could see it wanting to rip out of his hands. (thats when the palms started to sweat)

As he let her go, my hands started to shake!! It was like "poof" and it was gone !! (now my knees started to shake)

I throttled back as I got airspeed. It seemd to handle well and the motor being 1/4" high seemed to be ok. It also balanced excellent.

It didn't take long for the peanut gallery to start yelling "lower, lower" and "open it up". So much for taking it easy.
I rolled on the throttle and holy sh-t. It was like when the X-fighters in star wars hit that hyper drive. The DD just accelerated and the pipe really kicked in. (my knees, thumbs, hands, and stomach were all shaking now). I have never seen or flown anything this wild !! I admit that I lead a sheltered life, but this thing was fassst. Anyway, as I achieved full power and got up to speed (this took all of about .2 sec.) It started to flutter !!! All I could think of was the opening scene from the bionic man and Steve Austins space craft coming apart !! The flutter was not too bad, just a little noise and a slight wing wag. I put four flights on her and brought her back safely. I will post some pics later.
Thanks to all for the feedback on my questions.

RR
Roadrunner1390 is offline  
Reply With Quote
Old 10-01-2002, 10:43 PM
  #11  
ChuckAuger
Senior Member
My Feedback: (12)
 
Join Date: Dec 2001
Location: Pampa, TX
Posts: 5,133
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default So which prop??

Did you go with?? The 9X9??
ChuckAuger is offline  
Reply With Quote
Old 10-02-2002, 03:13 AM
  #12  
Roadrunner1390
Member
Thread Starter
 
Join Date: Aug 2002
Location: Hartford, CT
Posts: 53
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default prop size

Yeah I went with the 9x9. I figured that the motor can still use more fuel for breakin and it will not turn as much rpm. You know how it goes, if ya got, it ya use it. As it stands, it was way fast with the 9x9. It will take me a while to get used to the speed and get bored. I still need to find out why she is fluttering when maximum speed is achieved. It could be the servo rods or the covering. The servo rods are heavy duty but I have no guides to keep them from wobble. It was never an issue with the 46. As for the covering, one end is a little loose. I mean its not all wrinkly but it has a slight low spot. Well I will figure it out. And in the mean time, I will attempt to get another DD kit and put it together.

I read a thread that someone had put the servos in sideways along the main ribs and ran the rods inside. Sounds cool and less drag !! Just what I need right now, more speed !! I will modify the engine area to fit the rear intake and keep the engine where it belongs. Have you heard of mounting the servos like this ?? if so send me a picture or drawing of what it looks like. like I said I know kinda what it is but would like a second set of ideas !!

Anyway, Im working all week and might not get airborne until Sunday

I am working on my 1/3 scale pitts. I am putting a smoke system on it and giving it a checkup. I hope to crank the Webra 52 up also this weekend and watch the smoke pour out on the low passes

Overall I know that when this DF motor gets broken in, and I drop the prop size it will really kick my a--.

I will get some pictures to ya. my web cam is a little fuzzy. I am waiting for a friend to come over with the good stuff.

Thanks for the advise, and look into the side mount on the servos for the DD.

See ya

RR
Roadrunner1390 is offline  
Reply With Quote
Old 10-07-2002, 12:34 AM
  #13  
WRXlovr
Senior Member
 
Join Date: Jul 2002
Location:
Posts: 142
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Re: Higher thrustline on DD

Originally posted by Dave McDonald
After my plywood motor mount cracked, I sandwiched it between two pieces of 1/16" aluminum. Like you, I was also worried about raising the thrustline. But after flying the DD with the TT Pro 36 (shown), and then a piped K&B 7.5cc DF, I couldn't tell any difference at all in the way the DD felt inflight with the raised thrustline.

Therefore, I don't think that raising the engine 1/4" will make near as much difference as you think it will.....if you can even tell the difference at all.
that aluminum is WAYYY too much,thats overkill and too much weight.All you need is two peices of .20 thick fiberglass
WRXlovr is offline  
Reply With Quote
Old 10-07-2002, 02:17 AM
  #14  
Dave McDonald
My Feedback: (19)
 
Join Date: Jan 2002
Location: Eldon, MO
Posts: 1,856
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Re: Re: Higher thrustline on DD

Originally posted by WRXlovr
that aluminum is WAYYY too much,thats overkill and too much weight.All you need is two peices of .20 thick fiberglass
I agree with you that .20 fiberglass plates would have been lighter. But I didn't have any readily available.....and I did have some 1/16" aluminum.

On the other hand, the total weight of the four 1/16" aluminum plates is only 1 ounce. I don't know how much two .20 fiberglass plates would weigh, but on a seriously overpowered 2.5 pound airplane, I'm not so sure that saving literally a fraction of an ounce would really be all that noticeable.
Dave McDonald is offline  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service