crooked stripe

New to gas engines. Installed a 20 DLE in a plane and am very happy with it. Expect the noise. I was told to change the prop. I am getting a lot of cracking from sound barrier speedsof the prop. I am running a 15 x6 but going to try a 16x6 hoping it will slow down. What do you all know about mufflers and where to get them. I don't want to be asked not to fly that plane at our field. All info will be appreciated, John

dmowery

Dont fly without one Any Hobby shop that sells planescan -contact DL and they have or know where to get one

RCVFR

My Feedback: (7)

You are under propping the engine. Try a 17X6, shd get around 8300- 8500 rpm.

BarracudaHockey

My Feedback: (11)

Quietest you can get for that are cannisters but they aren't cheap. But even can's wont help with prop rip.

opjose

Given the RPM's what you are hearing is coming from the muffler.

Your prop is not approaching the sound barrier.

All too often people confuse engine sounds with prop sounds on smaller gassers like yours.

Your muffler is an unbaffled "can" type muffler, which is almost as noisy as running no muffler.


FYI: Syssa makes noise quieting restrictor inserts for their engines.

I was in the same situation as you, where the so-called "experts" kept telling me that my engine was noisy due to prop noise and I should change my prop.

To that I merely answered by installing the inserts and starting the engine back up.... they went off to remove the remnants of their foot from their mouths....

Check out the Syssa "tone" inserts, in lieu of installing a canister you could opt for making and installing something like that. It seems easy to do.


We have several DLE 20's on our club trainers and yup, they are noisy, and no it's not the prop.

acerc

J-Tec also has silencer's.

crooked stripe

I will look deeper into some sort of muffler. I saw the muffler inserts from Syssa and I was going to buy but I found no size or price listed. I did see that If you bought one of  their motors you could purchase the inserts. I gave them a call and got nothing but an answering device. Hopefully tomorrow they will call. I will now look into J-Tech and see what I can find out. Thank you all for the response. I will post to let you know what I do. Thanks again, John

acerc

You could always do the steel wool up the pipe. I have one that way and it's quite as a mouse.

opjose

I don't think the Syssa muffler with fit the DLE 20.

I used them as an example of one solution that works fairly well and does not look hard to replicate with a little light metal work.

opjose

I've seen several people recommend this...

I would like to try it but I have a nagging question for you.....

Steel wool ignites VERY EASILY ( just take a match to it and see ), and it doesn't need high heat for ignition. A small spark is enough to get it going if it is heated.

Given that the exhaust on a gas engine is basically a hot flame on the virge of going out, doesn't the steel wool ignite while in the muffler?

Have you ever looked at it or removed it after use?

Does it still feel and behave like Steel Wool after it has been removed, or has it turned into brittle oxidized metal?

I'm afraid of the latter getting back into the cylinder head accidentally.

If it does ignite I wonder if something thicker and less prone to ignite might work just as well, such as the heavier steel wire often used for drain traps?

The stuff sold for catching lint coming out of clothes washer hoses may do an even better job.

tailskid

My Feedback: (34)

Isn't there some 'exhaust' direction and some 'blowback' INTO the engine with every stroke in a two stroke engine? Won't that suck the steel back into the engine?

Mk23socom

My Feedback: (7)

I think he is leaving out a key piece of info here.. The steel wool that us as modelers are accustomed to using and seeing is mostly the very fine stuff used for buffing when weathering and things such as that.. At least that's my opinion about it. I used to use it alot as a kid but up until just now, totally forgot about the coarser grades of the steel wool. I THINKthat is what he is refering to rather than the fine stuff that you may be thinking about. Otherwise, I agree with your concerns exactly.

opjose

Yup it would stand to reason that thicker steel wool requires a higher ignition temp, but I don't think the difference is excessive enough to warrant using steel wool in the muffler.

I'll need to test a thicker grade wool with a match to find out though.

I do wonder if those thick stainless steel meshes used for lint catches would be a much better solution.

opjose

Yes, especially if any of it combusts or corrodes...

Gray Beard

My Feedback: (-1)

For a few bucks try a 17X6 Xoar prop on that little engine. Other then changing over to a pipe most everyone I fly with is using the stock muffler. They work fine as they are. Even a Xoar 16 inch should be better then the 15. You want a prop selection anyway and they are a bunch cheaper then a new muffler. The 17 may be just a tad big.

opjose

Yeah that's a good combo.

We have three Telemaster's with DLE 20's as our club trainers.

We tried the 17x6 prop on them but found that the engine is FAR too powerful for this 70-90 sized plane for training purposes... even with the throttle maxed out at 40%!!!!

Each landing cost us a prop too...

So we stepped down to smaller props, which of course made the engine louder with the higher RPMs.

bbbair

Hey Guys,
I just saw the same question & this answer the other day on a different thread - yours to consider...

From a fellow in Kansas City Mo;

On my DLE 20 I plan on finding some brass tubing that is a tight slip-fit into the exhaust stack, drilling a series of holes in the top of it, and then inserting it into the exhaust stack. I will secure the tube with a sheet-metal screw.

This will act as a baffle and increase the silencing effect. I noticed the DLE 20 muffler has no baffles and the exhaust can exit the engine and go directly down the pipe. This is likely why it has been described as a bit on the loud side. I will put in the stainless steel stuffing as well and that should take care of the sharp tones.

I have done this process for years and most bystanders have commented on a "mellow" tone. When I feel the need for speed and lots of noise, I get out one of my old Quickee's with a short pipe and have at it!

(The stainless steel stuffing used, is scouring pads and you can get it at hardware stores.)

What I plan to do is use the brass tubing and leave out the stainless steel wool on the first trial and add it IF REQUIRED.

opjose

Scouring pads use relatively fine steel wool, which easily combusts.

I don't think this is a good idea.

Gray Beard

My Feedback: (-1)

Just adding in brass tube with holes drilled into it will quiet them down but also adds back pressure. The trick would be hitting the engines happy place where it doesn't harm the engines performance. I just got my new Tower catalog yesterday and saw Bisson is making mufflers for DLE engines. I thought of ths post right away. They don't have the 20 listed but if you phone them they may have them for the 20 but didn't make it into the catalog? Bisson mufflers have baffling and are very quiet. I use them often on glow engines. If they have them for the 20s that may be another way to go.

opjose

Thanks for the info!

I guess we'll be calling them for our club trainer's engines.

Gray Beard

My Feedback: (-1)

Perhaps it's because of the very open area I fly from but I haven't noticed the DLEs being that loud? One fellow did have a big twin that was ear shattering one day, I knew he had just changed canisters and thought it was that but the next day it was quiet again, all he did was changed the prop to a different manufacture and it was quiet again. I just don't recall what the loud prop was and what brand he went to the next day.
Post up if Bisson has them for the 20 yet? There mufflers are real mufflers, not just open boxes.

tailskid

My Feedback: (34)

We just had a DLE55 get a "NO FLY" because he was at 108 Db this last saturday...don't know what prop he was using, but I don't think he was even at full throttle (@10').

opjose

Personally I don't find them loud.

I think the higher pitch tone of the small engine tends to be more annoying, so people perceive that as an increased sound level.

KWJ48

I'm loving my DLE 20 with a 17x6 JXF prop.

Here's a silencer from Valley View. I've bought from them before, good company to deal with.

http://www.valleyviewrc.com/estore/m...cc-111cc.html#

bbbair

Here is what you are looking for;

http://www.bissonmufflers.com/en/muf...mageField.y=10