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60lx high performance help.

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Old 05-16-2008, 09:10 AM
  #1  
darren94
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Default 60lx high performance help.

I just got my order from jett for my sundowner 50 and everything is great except for keeping the muffler extension on the pipe. I have the plane set up like the pictures on the jett website (exhaust through the firewall then out the side) and i had to add an extension to get the exhaust diverted. I started with the rubber deflector and it melted the zip tie. Then used a hose clamp. Hose clamp vibrated loose within 1 minute. So, i got a custom mandrel bent copper pipe to go from the pipe to the outlet and then hose clamped it as well. No luck pipe came off within 1 minute. Lastly, i i jb-welded the pipe to the copper diverter and still no luck. The pipe broke the weld in 3 minutes. So, i have not been able to run the plane for "break in" for more than 5 total minutes. any help would be great. I am guessing that the vibrations are causing this issue and i need to soft mount the pipe. Help please.
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Old 05-16-2008, 11:34 AM
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Default RE: 60lx high performance help.

If you are using a plastic engine mount, the thing is going to shake like crazy. The kit mount is designed for a 4C engine, and is way too long to properly support the power output of a 60LX without moving around.

Needs a metal engine mount.

If it is shaking off a rubber extention or a JB joint, its definatelly shaking very hard. Trying to constrain the engine assembly by mounting the muffler will cause other problems (will rapidly break the muffler screws or the muffler itself)


Be sure to set everything up on the test stand and run it there first - including the exhaust extention. Ensure you are using the correct break-in prop size (9x6 or a 10x6 clipped down to 8" diameter works well).

Do not attempt to break-in the engine on the aircraft. You might get away with that with a TT46, but you will not be successful with this engine.

There are too many variables involved (including vibration as you can see). The test stand is a controlled environment, and you run much less risk of inadvertantly tosting the engine due to something you can not control. Just the fact that you said you melted a nylon tie wrap is concern enough that the engine has gotten extremly hot in the current process.
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Old 05-16-2008, 12:39 PM
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Default RE: 60lx high performance help.

The motor has been through maybe 2 tanks total at 17k rpm on a 9x6, 6 turns out running so rich that the plane is dripping with excess oil and fuel. Running lean is not an issue here.... on the other hand, the motor mount is plastic but the problem is the pipe extension coming off. I feel that there needs to be a "buffer" at some point within the exhaust system. The metal head, spacer, pipe and extension just relay the vibrations down the exhaust and airframe. I am going to try and install the 60-90 size GP extension onto the pipe and then use a modified copper pipe to exit the airframe.

Should i use hose clamps? wire ties or zip ties?
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Old 05-16-2008, 10:53 PM
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Default RE: 60lx high performance help.

The 60-90 size is definately required...... use that. The 40 size is too small in inside diameter and causes the engine to run poorly.

I just use a piece of 3/8" id silicone hose (1/2" OD) myself. Same stuff I use to slide over helicopter skids.

I just use the 1/16" wide zip ties. Hose clamps will cut it. sometimes a tiny bit of red (hi temp) RTV at the diverter install point helps that little extra bit. Clean the tube and muffler well, and let the rtv set up for at least a day.

As for running at 17K with the 9x6 rich like that is not good when it is new.

It needs time on the test stand following the break-in proceedure. You want the engine up around 18,000 - 18,500 with the 9x6 prop - it will still be slightly rich, but the important part is it has to be up at rpm.

Only mount the engine and muffler at the engine mounting lugs. If you tie the muffler down (or for that instance, if the muffler is touching or bound by the airframe anywhere), it becomes part of the engine mounting system and something is going to break.

I caution again about the plastic engine mounts.
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Old 05-17-2008, 02:43 PM
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Default RE: 60lx high performance help.

Ok, here is what i have done.

installed 60-90 size deflector with advised set up.
broke off 4 times in 5 minutes.
Repeated 3 more times.
NO LUCK. (even dremeled the lip on the pipes exit to give something more to "grab on to)(made lip bigger)

Then,
Removed engine from plane and installed on test stand.
Attempted to break engine in
Within 2 min of running 18k on a 9x6, the pipe bolts broke off and have studs stuck in pipe.

This setup is not working out. Something is wrong.

Motor starts right up, powers up well and runs on the rich side at WOT (18k) In or out of the plane. When the motor is in the plane, it blows the diverter/deflector setup off EVERY TIME. Out of the plane, it has now broken off the pipe and i am att my whits end with this thing. I have enlisted the help of one aero engineer and one mechanical engineer who have been building/flying 20+ years.

PLEASE HELP. I am ready to use this as a boat anchor and cut my losses.

Please note, Prop is a 9x6 APC balanced, the pipe in or out of the plane is not "mounted" or restricted in any way.
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Old 05-17-2008, 06:59 PM
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Default RE: 60lx high performance help.

You have some good help there, and it appears you have a good modeling background.

The same shaking that causes the diverter to come off is what fatigued the muffler bolts. The bolts are intentionally the weak-link in the system, so they shear off like that should a crash occur to protect the muffler and crankcase. They are usually not difficult to remove.

The engine requires a solid engine mount.

The engine is not rocket science. But this particular engine does 100% require that it be used and broken in per the instructions and direction provided. It is not an OS or TT engine where you can get away with just about anything. It will run hot and blow plugs if it goes over the edge or is not afforded the right cooling setup.

If required, send the engine and muffler back to Jett. He can remove the screws if you are unable to.

If you are not satisfied with the performance or are unable to utilize the engine, it would be best to simply request a refund.
jettengr@sbcglobal.net

Short story on the diverter...... vibration and heat will cause it to fall off. I have had them fall off too. The one on my funfly plane has been on there for 4 years. The one originally on my Edge drove me nuts until I had everything dialed in properly. Make sure there is adequate cooling in the cowling. Close off the un-used cowl inlet side if it is cut out. The bottom of the cowl must have a cooling air exist. Even though the engine is rich, the exhaust temperature and muffler temperature can climb rapidly.

The other reason for setting up everything on the test stand first is to ensure it works as a system. You have to understand how the engine operates. Once it works and you have a reference point for adjustment, rpm, etc. If there is a problem, that is the easiest place to make corrections or adjustments. Then if you install it in the plane and it doesnt work, something runs weird, or something falls off...... you know 100% it has something to do with the aircraft installation.

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Old 05-17-2008, 07:13 PM
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Default RE: 60lx high performance help.

One other thought here I will toss in......

The prop drive stud (threaded prop shaft)

Remove that from the engine, thread it back in, and ensure you back it out 2-3 turns. You do not want it tight or bottomed out.

If it does bottom out, the shaft can sometimes cause a prop to mis-align when tightened. The threads on the stud pull to one side when tight. When it is loose a few turns, the shaft "floats" a bit, but remains centered. When you tighten the prop, the drive washer, not the shaft, aligns the back of the prop.

That condition has driven many folks batty. It acts like a bent crankshaft, but because of the jett design a "bent shaft" is not possible. On racing engines it has caused muffler bolts to shear in flight. And on one occation where someone poorly mounted a receiver, it failed a crystal.

Causes some very high frequency vibration that is not explained otherwise. Sometimes it is not even obvious. That vibration is VERY amplified if the engine mount is in the least bit flexible. If you have ever seen a vibratory feed device work in industry, imagine that on steroids

Worth checking.
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Old 05-18-2008, 01:50 PM
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Default RE: 60lx high performance help.

bob. i am planning on caling this afternoon/evening.
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Old 05-19-2008, 08:26 AM
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Default RE: 60lx high performance help.

Bob,

I would like to send the motor back to have the broken bolts in the pipe fixed and have the motor correctly broken in/setup. I am having no luck with this i feel that the required break in process is causing more harm than good due to the fact that the system will not stay together for more than 1/10 of a tank of fuel. I feel that if the the company can set it up, break it in, set up the deflector and send it back to me after it has been tested for this setup, i would be very satisfied. I will pay to ship the unit back to Jett and possibly for the metal engine mount (if needed).

Please let me know what i need to do from here.
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Old 05-19-2008, 09:18 AM
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Default RE: 60lx high performance help.

Ship it back. Address is on the website.

Include a note with all of your contact information, a description of what is desired, and note that you have been speaking with me regarding the engine.

Email Dub at jettengr@sbcglobal.com and provide the same info.

Once re-assembled Dub will bench run the engine.

Installing the diverter is possible. Ensure that you note what orientation you are looking for (angle). Running on the bench completely set up will ensure the engine is running 100% before it is returned.

While the engine is out, look into a replacement set of engine mounts. There are a few companies that make "ARF retrofit" alumium mounts that are the same size and mounting pattern. I dont have a link handy, but I have seen them out there. Alternately, Dub has a mount setup defined for the Sundowner installation - including the proper spacers. You may wish to ask about that as well.

Bob
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Old 05-19-2008, 09:25 AM
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Default RE: 60lx high performance help.

Bob, I thank you for your help! I will keep you posted on how it turns out.
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Old 08-01-2008, 03:21 PM
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Default RE: 60lx high performance help.

Bob, looking at the 60lx and other engines for a delta diamond dust on back order. I will sheet balsa and coat cabon fiber glass and reinforce key areas with the idea of top speed. Is the 60lx engine the fastest available... I read about and have access to hi nitro 40 and even 60%. I heard about engines that can run upto 30k rpms and get a lot more speed and hp. The 60lx is your hottest engine in this size class, what about your racing engines...

I don't want to modify engine for higher octane, but would like something designed for max rpms and nitro
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Old 08-04-2008, 09:04 PM
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Default RE: 60lx high performance help.


ORIGINAL: claytucker

Bob, looking at the 60lx and other engines for a delta diamond dust on back order. I will sheet balsa and coat cabon fiber glass and reinforce key areas with the idea of top speed. Is the 60lx engine the fastest available... I read about and have access to hi nitro 40 and even 60%. I heard about engines that can run upto 30k rpms and get a lot more speed and hp. The 60lx is your hottest engine in this size class, what about your racing engines...

I don't want to modify engine for higher octane, but would like something designed for max rpms and nitro
Hi Clay......

You do not want to use 40 or 60% nitro. Requires a very specialized engine setup. Keep in mind, the fastest of all planes racing out there are FAI ships, and they use ZERO nitro.

The FIRE 60LX (or better yet a FIRE 50LX) is the fastest thing we can offer for the diamond dust. No, you will not see 30K rpm. The engine is typically set up with the pipe and header to turn 18,500 peak ground rpm with a 8.8x8.75 prop. Unloaded in flight it gets up around 20-21K at most. That is the best performance for the delta type aircraft. This is on regular sport 15% fuel. You can push up to 25% or 30% fuel (heli fuel) if you want.... quite a few run the heli fuel jsut because they have it... and its good for another few hundred rpm.

Next best choice is the regular SJ-50 side exhaust engine, add the "racing" muffler. Easy setup, very verstile .... no pipe mounting hassles. Performance target is agin in that 18,000 peak ground rpm range.

The QM40 engines turn around 23K on the ground and approach 28K in flight - and the produce about 3 HP or so but that is with the carbon 7.4x7.75 props. That setup will not really perform well on a draggy delta plane that has to be hand launched. It has been done, but folks using the lower rpm and full bladed 8.8" or 9" props tend to have faster setups and better flying aircraft.

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Old 08-08-2008, 01:11 AM
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Default RE: 60lx high performance help.

thanks ok I am learing a bit more about the higher perfomance engines. I've had a dozen engines and 5 yrs of flying rc and most of the time with high speed wings BUT of course I am still learning. I just heard and saw some difficult launches on deltas with the small prop quickie engines. I got it, that's out of the question

Luckily, I was able to purchase a whiplash (new and was stored away in the box) hopefully it arrives THEN i will call and make the order.

The whiplash is heavier then the diamond dust but a similar design. I know there is a limitation on the tank, is that why you would recommend the smaller engine..

Or could i make room to get one of your larger tanks in and get faster speeds from the 60lx fire. also you mentioned just 500 rpm difference on the sj50 vs 50 lx and no need to build pipe set up and is a bit cheaper. Pipe is still exposed so I guess there would not be much of a difference in speed (few miles per hour) but it's a lot cheaper and it still uses the same 8.8 8.75

your engines don't run that much higher rpms, you don't rate h.p., they are more difficult to break in but you are suggesting a much higher pitch and still show higher rpms then say O.S. or Weber. any idea on the hp on this engine. Of course, i will see a lot more speed out of the set up...
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Old 08-08-2008, 09:14 AM
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Default RE: 60lx high performance help.

Factory published HP numbers and rpm quotes are not much use. There is no standard way in the industry to test and publish those numbers. Also, HP and rpm are always published together because they are inter-related (HP = torque x rpm). You will see often some HP noted somewhere as 2.2 HP at 18,000 rpm, when you know darn well the engine will never see more than 14,000 rpm with a useful prop load on it. Jett doesn't publish HP because, again, its meaningless for comparison. The only true way to compare engines is by evaluating them under a standard useful load (a prop).

Jett choses the load approach, and guarantees the engines hit the minimum published rpm. In fact all of the engines are run before they are shipped, and they must meet minimum performance standards or they do not go out.

Also, do not confuse displacement with power. A .60 is not always more powerful than a .40 - depends on how it is set up for the application. Also keep in mind, the jett 60L is the same crankcase size as the 40 and 46 .. appx same weight and size for all 3 engines.

For the whiplash, the 8.75", 8.8" and 9" diameter Q-500 props are ideal when using the Jett 46, 50 or 60L engines. Standard blade 9x7 and 9x8 are great too and generally provide a better launch at the expense of a little top end speed.... typically a good trade.

You do not want to use a 25,000 rpm QM40 engine with the 7.5" prop, if that is what you are refering to... no way to effectively launch a whiplash with that setup.

The sport-jett engines are among the most user friendly and easy to operate engines you will find anywhere. They are just a bit more powerful than most. For this reason, and considering you are learning a bit still about engines and applications, I recommend sticking with the sport-jett engines such as the SJ-46 or SJ-50 (both side exhaust). If you want a bit more, the FIRE 60LX will give you top end performance slightly greater than the Q-500 engine, and it idles and transitions well.

Tank capacity does not really play in here.... you are going to get 3-4 minutes of flight time at most with any of the engines with the 6oz tank. You can use a standard fuel tank, just be sure it is padded and installed well.


Whiplash style bubble-jett tank

Lots of whips here
http://www.jettengineering.com/hall/hall-delta.html

Bob
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