Quiet blower?

The dump gate seems like the way to go on that one. It's quiet enough to have near the furnace without being a burden and easily adjusted, but I sure like being able to just turn a knob.

Pete

 

I've got a bouncey blower in my attic that I just cant seem to stick in a garage sale. I know the moment I do, I'll want it for something..

 

Added inline ball valve to further control airflow (in addition to HF speed controller). Was needed since speed controller's min setting is 50% pwr.

Pretty happy with result but will still work on modifying work area to make it quieter. Next target, my pancake compressor. Need to get an extra regulator and really long air hose, so I can keep compressor in garage.

 

Just replace that pan cake oil less airless compressor with something that takes oil. They are the noisiest most unreliable pieces of shit ever made. Just wait, you will be mid melt and the shitty reed valves will pack it in on you. We were in the middle of painting a truck in the 1990's and had a tall crapsman compressor that did just that. Expensive disaster to say the least!

 

Just be careful. The speed controller you are using is unpredictable as it is a chopped sine wave. Most motors have a fan built in to adequately disperse heat. When you're running a motor at 50% speed, with 100% amperage, the cooling is not there. This is where pulse wave modulation has excelled in the past 10 years. Motors are stupid but restricting motors from the original design is a bit silly unless you do it right.

Any motor that you actually really on, or care about.... Should be tested properly.

My blower runs on a VFD. The motor is pretty happy at most speeds as they are compensated with the volts and hurts. When you use a Vfd and you are running at 50% RPM of the motor, you're running at 50% of the horsepower. When you're using using chopped waved controller at 50% you are at less than 50% of 50% of the full speed amperage. More or less at 25% torque with 50% heat. This is why burn out happens so quickly.

Static converter's are for the starting only. They use capacitors and there is a flat spot. When using a 3 phase motor, you will only get less than 66% of the full FLA. This is when using single phase input.

Using a router speed controller that should be used at 10,000 RPM motor... on different type of motor that is only 3450 RPM, it does not work the same! Why? It's just like your Honda Civic doesn't work the same when it has a trailer of 4000 pounds of gravel behind it, and you have shut down two of the three cylinders! Does this make sense?

I work with guys that have $1000 motors and don't want to burn them out. Usually with three phase vintage woodworking machines purchased at auctions. Usually the machines they purchase or less than $2000, and it's worth converting them to single phase using pulse wave modulation.

Show me your motor specifications or motor tag and I'll give you more information.

 

THERE IT IS! Thanks, I knew you could explain it better than I could.

 

Motors are stupid. Give them the what they want and they work perfect. Give them a dimmer, only ask for them to give 25% less than the dimmer setting. Dimmers were made for lights, not motors. Putting a dimmer on a motor will kill it very quickly if power or amperage needs are required. Work required!

A motor has 6 to 10 times amperage required to start it. Slow starting it with different controls have different outputs.

Now this is true with DC or three phase motors with proper speed control. Both these motors can be put into high torque settings for a short period of time. But, they usually have overloads for internal coil heat overload. This is why the Tesla car works so well..

 

Any of your universal brushed motors like angle grinders, drills, bouncy castle blowers and vacuum cleaners actually run well off cheap thyristor based speed controls so long as there's enough cooling airflow. That's why those cheap routers and dremel clones tell you not to run them for long at the lower speed settings as the cooling fan barely works at those speeds, even if there's less wattage dissipated. Thyristor based dimmers and speed controls actually have voltage feedback which means they'll feed a bit more power in as the mechanical load increases which improves the speed stability under load...still not as good a variable frequency drive but the cost is a lot cheaper. Where the thyristor based light dimmer controls have problems with inductive loads is that there's a respectable back EMF voltage coming off the motor that can affect triggering of the DIAC/TRIAC combo and light dimmers don't account for this where dedicated motor speed controllers do. Brushed universal power tools will even run off DC power: I have a 5" Hitachi grinder I run off rectified (but not smoothed) mains fed into a 5 KHz pulse width modulator to chop up the voltage to the grinder and get variable speed down low. It does bog down a bit more than an old school thyristor controller does.

As far as blowers go, if you have a centrifugal blower with involute curve blade profiles, they are quieter than the blowers with straight blades which are similar to air raid sirens in some ways as I found out the hard way.

 

With my set up, I can tweak almost any sweet spot. I'm building some charts with each melt. Before I light the furnace, I try to set (or preset) the fuel to 100 mL per minute. Now I've been trying to set the blower up to a previous melt speed.

I'd like to measure the liquid fuel in millilitres per minute, but I like to measure the air at cubic feet per minute and I've been testing U manometer water pressure.

I am finding a sweet spot at 100 mL per minute with 30 to 40 CFM.

A really quiet fan would be a bathroom fan. But most bathroom fans require about 4" diameter piping to keep up the CFM. A 100 CFM bathroom fan being reduced to 2 inches ID pipe is about 1/4 or 25 CFM.

Something to always keep on the back of your mind is your air source, how long of piping do you require for your air source, and the smallest restriction of the air source.

Static friction veers its ugly head. Pardon the pun but it's there. I am using high velocity low pressure air or HVLP, but I'm not a good example.

 

As it turns out, I need a lot less blower pwr than I originally believed. Certainly, much less than my smaller 8 inch diameter propane furnace required. Not sure what black magic physics is going on here

I can probably get by with a smallish centrifugal blower. Shop vac seems to be over-kill. Time to check out what amazon has to offer. If I had time, I’d love to build one. Unfortunately, my COVID work hiatus is coming to an end soon.

Ran a test today to dial-in a good blower speed for my current furnace when pre-heating with propane. Not the most scientific approach but still enlightening. Put a large oblong quartzite rock into furnace with long axis length about 11 inches. This left about a half inch on either side.

Quartzite gives off a nice red glow when sufficiently hot, so it’s easy to see if all sides of rock are heating up. If blower speed is too high, non-burner facing portion of rock will remain relatively cool while the burner facing side glows red hot. Basically, you’re blowing heat out of furnace instead of using it. Only portion of rock in direct contact with flame gets hot enough to glow. Rock will heat-up/glow more uniformly when fuel/air mix and blower air speed are good. For me, at least, an oblong quartzite rock is a better indicator than a crucible.

I need to repeat test when running on diesel, but I expect similar results, i.e., requiring much lower than anticipated blower speed. I think that this is why I couldn’t do a cold start on diesel. Blower was providing way too much air. Based on feedback on topic, I already suspected that this was the issue. Live and learn.

 

Can you show us some pictures of your burner torch and set up.

 

Will take some picks next time I’m up and running. Probably on Monday.

Due to on-going experimentation set-up is evolving. Shop vac as blower will likely be replaced in near term with something lower power. This will allow me to do away with ball valve, air redirection set-up that I’ve used up to now to regulate blower air flow into furnace. However, the burner will likely remain the same.

Burner Is pretty straightforward. Using a .85 GPH delavan siphon valve . 1/4 inch pipe feeds compressor air to nozzle. Fuel line is not pressurized. 1/8 inch copper tubing feeds fuel into nozzle. Using schedule 40 black iron pipe with 2 inch ID as tuyere. For some reason, early on, seemed like a good idea to have tuyere pipe cut to 36 inches. Probably just desire to have a good stand off distance from furnace when it’s running. This, of course, meant that 1/4 compressor air pipe would be cut to same length.

Haven’t added a spin vane. Not sure how necessary it will be. Plus, I don’t have machining equipment to make a decent spin vane.

Originally, planned to remove 36 inch, 2 inch ID pipe when furnace was not running. However, removing and reinserting pipe several times put too much stress on refractory causing an unfortunate crack where pipe gets inserted into furnace. It’s a tight fit. Good seal around pipe, so no hot air/gas escapes from insertion point. So, now pipe needs to stay put.

 

My burner compared to yours is like a toy. My welding job wasn't the best. I struggled!

 

Sounds like you’ve instrumented your set up really well. Much more sophisticated than my Fred Flintstone-Rube Goldberg love-child build.

 

I doubt it. I thought I was a ok welder. But this took me for a spin. Fine-tuning air and fuel ratios has given me a new spin with temperatures.

 

@OMM,

I just changed the fuel delivery part of burner. Previously, had 1/8 inch copper, but that was just too fragile. Switched to 1/4 inch pipe.

Also added regulator inline on burner compressed air intake. My compressor side regulator was just too flaky below 20 psi. Also, lets me keep my compressor in garage for noise reduction. So much more pleasant.

Unfortunately, my compressor regulator’s flaky behavior caused me to partially melt nozzle o-ring. Still can use it in a pinch, just loose some siphoning action if fuel valve is not at least half open.

Just need to find where I can buy o-ring replacement

 

Ebay
https://www.ebay.com/itm/Waste-oil-...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2648