I'm completely new to R/C flying and I have a couple of questions regarding field gear.

1. I have seen voltmeters available at hobby sites that seem to be manufactured specifically for R/C modelling. I already own a multimeter with all of the typical functions (I use it mainly to measure voltage on my NiMH rechargeable batteries used for a digital camera) Is there something special about these R/C voltmeters which would require me to buy a new one, or is my current multimeter likely to be fine??

2. I notice there are glow plug starters which plug into the power panel, and there are glow starters which have a NiCad battery so there are no wires. Is one preferred over the other, or do most people have both??

3. Is there a cheap way to balance props or should I spring for the gizmo they have at the local hobby shop?

I know I should probably attend a flying club meeting soon, but I'm about to relocate to a different city and I don't want to take advantage of some club when I know I'll never become a member there...

Thanks,

Darren
Chicago, IL

I've never seen the need for a specialized multimeter and have used my Micronta digital multimeter for years.

The small handheld glow plug starters are handy and the voltage is usually right for most glow plugs. They are I suppose especially nice for firing up your average B-36 model with 6 engines and a 12 foot wingspan but offer less advantage for a single engine model particularly with an electric starter requiring power from the field box anyway.

Glow starters that plug into the power panel on your field box are nice in that you run off your 12 volt starter battery and never have to worry about charging them or having one go dead in the field. You can also adjust the voltage to get exactly the right glow plug temp, which I like. In my opinion the important thing with either type is to get one that locks securely on the glow plug and will not fall off as soon as you spin the prop with your starter. That can be really annoying.

I think the gizmo they sell at the hobby shop IS the cheap way to balance props. The question I think most people would ask is how badly do you really need to balance your props.

The specialized voltmeters for R/C are the analog "ESV)" (Expanded Scale Voltmeters. There's a couple of digitals showing up labeled for R/C use... but that's another story.) Compared to a good quality digital voltmeter... the ESV doesn't have any advantage. The ESV is a big improvement on trying to get a reading on a RX pack with a standard analog multimeter. A good digital meter will outperform the ESV every time.

I prefer the glow "ignitor" which is a C or D cell NiCd and glow plug clip all in one unit... no wires to get caught in the prop. The Power Panel with the glw plug "driver" (a large resistor and a rheostat for fine tuning, with an amp meter indicator) WORKS... but the wires are a big hassle. The C cell size Glow Ignitor will give a lot of engine starts between charges. When I fly a LOT (5 to 10 flights per session, 2 sessions a week) I charge mine once a month. (and I'll be loaning it to others... so it averages over 100 engine starts per charge.)

The fingertip prop balancer by Great Planes is the cheapest I'd rely on.
You CAN balance a prop by putting it n a music wire, or brass tube and spinning it. Before the first spin, mark one blade with a magic marker, and note if one blade tends to be low every time the prop stops spinning. Lightly sand the FACE of the heavy blade. That will rough in the balance of any prop, and is adequate for general flying until you can get a good balancer.
To be accurate... you need the balancer rig that has a stand.

Prop balancing is important to consistant engine operation. an imballanced prop leads to fuel "foaming" in the tank, mixing air bubbles with the fuel going to the engine. This makes the engie very hard to adjust at best... and can cause lean engine runs (damages the engine) and can cause unexpected loss of power at a critical time. (steep climb from take-off, not enough altitude or airspeed... engine dies and the plane is doomed.)
Consistently using imballanced props can also lead to premature engine bearing failure.

<blockquote>Quote
<hr>Originally posted by: snoopy10
I'm completely new to R/C flying and I have a couple of questions regarding field gear.

1. I have seen voltmeters available at hobby sites that seem to be manufactured specifically for R/C modelling. I already own a multimeter with all of the typical functions (I use it mainly to measure voltage on my NiMH rechargeable batteries used for a digital camera) Is there something special about these R/C voltmeters which would require me to buy a new one, or is my current multimeter likely to be fine??[/b][/i]<hr></blockquote>

In order to accurately check the in-flight battery pack, you need to place a load on it. I don't know whether that is what the commercial units do. There is a construction article on my web page for a unit that you can make for about $3.00 that will do this and allow you to use your existing VOM. The unit was designed by Red Schoelfield who is a recognized authority of batteries within the modeling community.

<blockquote>Quote
<hr>2. I notice there are glow plug starters which plug into the power panel, and there are glow starters which have a NiCad battery so there are no wires. Is one preferred over the other, or do most people have both??[/b]<hr></blockquote>

I have both the plug-in type ignitor and the clip-on ignitor. I used the plug-in type for several years and always felt uncomfortable having a wire that close to a spinning prop. I still keep it in my field box strictly as a backup should my clip-on ignitor run down.

I also got a battery pack for my starter to eliminate that wire also but my Thunder Tiger engines start so reliably that I seldom use my starter. At this point, I hardly ever use my power panel anymore.

I agree with lightfoot about the voltmeter.....whatever you use should put a load on the battery to get a proper reading...also, the hobby-specific voltmeters can be switched between a 4.8 or a 6.0 volt pack.

I also have 2 glow plug starters...I prefer to use the Ni-Cad version because it has no wire, but I keep the panel plug-in type for a backup also.

I like the Great Planes prop balancer also....it's small, cheap, simple, and really does the trick.....I highly suggest you balance your props one way or another.......FHHuber described extacly what can happen if you don't.....

Mike

The voltmeter that are for R/C use have the abilility to switch between 4 cell batteries and 5 cell batteries. They also check transmitter batteries. I reccomend the ones for R/C use.

I have the glow starter with the NiCD battery. I don't like having the wirers hanging near a spinning prop. I think NiCD ones are safer.

Get the prop balancer. You should always balance props. If you don't you will get vibration damage and something will fail in the air. Unbalanced props cause fuel foaming and that will cause the engine to quit.

I hope this helps you.

The additional vibration from unbalanced props also does not do your radio equipment any good. Balsa fuselages are better at absorbing vibration than plastics or composites but balancing the prop and isolating the receiver with foam is still a good idea for your receiver.

Any metal on metal vibration can also cause radio interference particularly with AM systems. So reducing vibration and eliminating the potential for metal to metal contact (such as the throttle pushrod contacting the engine) will improve the reliability of your radio equipment.

And I'd agree you can balance a prop with a piece of tubing but if it isn't accurately balancing the prop, (and at 16,000 rpm accuracy counts) you are not really saving any money when it leads to a crash or dead stick landing. So again, the gizmo in the hobby shop is the cheap way to do it.

One more thought on vibration...even with the propeller balanced, the engine/prop combo and the varirous parts of the airframe will still vibrate and resonate at certain frequencies. When you get a prop that does what you want it to do, do a ground check to ensure there are no rpm ranges where you encounter sympathetic resonance.

If for example the horizontal stab is vibrating in harmony with the engine at a certain rpm, you will get a much larger amplitude in the vibrations. This can cause the airframe part in question to fail or at least will cause the joints to be highly stressed. (A good argument for using more flexible epoxy rather than CA for connencting firewalls and tail surfaces to the fuselage.) The increased amplitude will also cause a higher level of vibration though out the airframe with potential radio and fuel problems resulting. Theoretically the propeller could also fail, but I've never seen this happen in an R/C aircraft.

Normally if this is occurring, the airframe part will "buzz" or even visibly vibrate. If it occurs make a note to avoid operating in that rpm range in flight. It's normally not a big deal as long as it is not occurring at a throttle setting you use a lot (ie for take-off, climb, cruise or decent and approach to landing). If it is occurring in a critical range, you can switch to a different brand, pitch, or diameter of propeller and it may resolve as the vibration frequencies will be different with the differrent prop.

The voltmeters that are sold for rc applications are loaded for the proper loads consistant with rx's and tx's and will give readings more usfull for rc use. A standard multi=meter will do the same thing but needs to have the load built in to the probs.
I have had a bad experience with a field box bat powered glo=igniter. The bat was low and when the engine started the batt gave a voltage spike that burned the plug out every time. I used a whole card of plugs before I figured out what was wrong. Also using the power supply for the starter and glo=plug made for sometimes having low voltage to the plug and hard starting. I like to keep the power source separate for the plug and the starter

Another point:

I use a handheld glo plug starter because I start my planes from behind pushing the plane onto a mounted starter. I secure the field box against the work table, and as I push the prop nut against the mounted starter moter, it slides back and trips a micro switch which spins the prop. Meanwhile my hands are completely behind the plane. Wires to a glo connector would be impossible. It was a device manufactured years ago and I bought one and have used it since. I believe there are other makers but I don't know where and I believe there are plans for making the same type of device. Whatever I am always behind the aircraft which reduces the tendency to reach over the prop (very dangerous) to adjust the needle valve.

Roodester

I vote for the "wireless" glow plug ignitor. The wires in the prop issue is the primary reason.

I have also learned that when I use my electric starter, the glow driver circuitry in my Hanger 9 power panel compensates for the current drain of the starter by turning up the drive frequency, unfortunately, it doesn't turn the frequency back down fast enough when the starter motor switches off. This of course, fries the plug.

I balance my props on the shaft of a screwdriver at the hobby shop. If they don't pass the screwdriver balance test at the hobby shop, I reject the prop. I do not believe that at our small scale, we can really balance very accurately. In trying to do so, I suspect that we mess up the dynamic balance of the prop. Our propellors are part of a dynamic system, and like balancing the tires on your car, static balancing is not much use.

For .60 sized models and larger, balance is very inportant, but for the 40 sized and smaller models, I think a propellor must be WAY out of balance before it makes any discernable difference in performance, wear or reliability.

I too prefer the wireless glo ignitor because of no wires close to the prop. Do get one that locks on well though as if it comes off into the prop unpleasant things happen. Do be careful in using the glo ignitor that plugs into your power panel, it does NOT provide 1.2 to 1.5 volts to your plug but puts 12 volts into it for a short time followed by a period of no voltage so the average voltage is approximately 1.5 volts. i.e. it is a chopped 12 volt signal with about a 10 millisecond on time and 100+ milliseconds off time. The duty cycle is controlled by the adjustment on the panel to get a higher average voltage if necessary. You can not see this with a normal meter, you need an oscilloscope to view it. If the internal pulse width circuit fails (this is usually a LM555 chip), you will get 12 volts and blow your plug.
As far as prop balancers go, if you are using the fiberglass or plastic type props, you won't need one. Most of these props are quite adequately balanced. If you are using wood props, you will occasionally get one that is quite a bit out of balance.