William Robison

My Feedback: (3)

A little trick for freehand drilling small round stock: Clamp the drill bit in a vise, or even ViseGrip pliers. Put the work piece in the drill chuck. When you spin the drill motor and offer the work to the drill bit it will self center.

Bill.

meowy84

AndyW, thanks for the comp lesson. I was finally able to read those articles. Who'd thunkit computers could be so fun. LOL

As for the carb, it is somewhat similar to the one you have pictured on the very left (http://www.rcuniverse.com/forum/upfi...69/Nl28387.jpg) in your 1/31/2005 3:02:56 AM post but the body is still smaller. And it looks like it's cast. I will try to post a pic of it later.

I like your approach to idle. Although I'm new to 1/2A and to planes I do want to accomplish a nice reliable low idle. Don't ask me why but a nice idle and transition is more important to me that all out rpms or performance (since I'm mostly interested in scale).

Tom, I really like your approach and solution. My carb looks somewhat similar to yours from the size standpoint but it is yet narrower. I will definitely try to post some pics.

meowy84

BTW, can any of these 1/2A carbs be purchased anywhere? Like I said the only carb I have is the one from the AERO/AME .049 and the one on my NIB Norvel Revlite. We've already established that thew Norvel carb is not the best to work with (plus I don't like it's looks anyways) so that leaves me just the one carb to play with. With the exception of one Tarno carb that was on theebay about a month ago I haven't been able to find any anywhere (they seem to be like hen's teeth).

AndyW

My Feedback: (1)

M84,

The absolute best, in my opinion, 1/2A throttle was the G-Mark unit as used on their .06. While it only had a simple hole for the airbleed, it could be made adjustable quite readily because the body had plenty of meat. And, it was quality made with a detent spring for the needle valve and easily adjustable throttle arm. When Charlie's was around, I bought four and thought I was set for life. Three of these were donated to VA free of charge in over a decade of attempts to get them to duplicate it. VA has come up with a similar version which is a close second to the best made 1/2A carb ever, the G-Mark.

Pictured is a G-Mark on my version of the perfect RC 1/2A. The idle screw can be done up left or right or even the option for both sides. That would make it more versatile for more applications. For a side mounted engine, both the high speed needle and the idle screw on the same side would be the ideal set up.

If you can get a Cox RC .05 throttle, this one works well but the most impractical feature is the location of the adjustable airbleed. You can't adjust it with the engine running. You have to stop the engine, adjust and go again. A real pain. I also don't like the spring loaded needle valve. VA uses a much stronger spring and in practise it's the BEST spring loaded needle valve assembly ever. The needle itself is small and light and not subject to possible vibration issues like the Norvel units. Norvels run on ANY carb just fine as long as the air bleed is adjustable.

In all of this, the biggest issue is adapting the throttle to the engine in question. Most throttles have a round stem to drop into the crankcase. Fox, MP-Jets and Norvel are the exceptions. All work well but make the addition of other brands of throttle a more complicated task. Many times, I'll cut off the stems of old carbs (non throttle) and glue these on to the bottom of a trimmed off throttle body. I use JB Weld and have not had any failures that come to mind. Very little loads imposed here and JB sticks like gangbusters to aluminum.

I too demand a low reliable idle with excellent transition. This is doable with any engine, Cox Norvel and VA. A bonus is that its possible to have max top end power as well. Idle from 5K to 19K on a Tornado 6 X 3 is perfectly feasible.

Tom @ Buzzard Bluff

Thanks Andy. As you can readily see the only place I deviated from your instructions was in the round 1/8" stock that I found in my 'scrap' pile. As the body of the carb doesn't have a lot of 'meat' I thought that using it with a matching profile filed into the carb body would give a bit more area for the JB Weld to grip. Little if any more trouble than filing a flat on both carb and larger round stock.
I thought that my previous post might be a bit difficult to understand so, having 3 more of the VA carbs to modify, I started on another in order to take a pic that might show the critical step better than my poor verbalizations. The pic accompaning this post is a bit fuzzy but I'm still learning digital cameras and it's the best I'm capable of if not the best the camera can do. For comparison purposes the drill bit is .032 and NOT the final size of the airbleed passage. The piece of al. tubing in the pic is only to hold the parts seperated for photo purposes.

m84: I got the old style VA carbs from Larry Driskoll who very accommadatingly put them in his duffle and brought to Small Steps last June. If he can supply them the late-model VA carbs with the idle circuit already in place would be a far better deal unless, like myself, you just enjoy doing things the hard way. I certainly don't want to cause Larry a hard time if the carbs are something the VA manufacturerer and US distributor cannot or are unwilling to supply but it won't hurt to ask if we don't make PIAs of ourselves. The AP Wasp carb IS available from the distributor for a very reasonable price IIRC. HTH, Tom

AndyW

My Feedback: (1)

OMT
For Kit Bashing 1/2A Engines. This time, digiphoto of actual article. Note on the first page, the photo, at the very top shows a Hiscott throttle/muffler used on a TD .049. The plastic carb carrier of the TD was replaced with a Medallion version. The muffler had a baffle which was coupled to the rotating Medallion style spray bar. This one was loaned to me for appraisal and I found that it worked extremely well. Why it didn't catch on and isn't still produced today is a complete mystery to me. It was very well made and gave you a throttle along with an effective muffler. I was out of 1/2A at the time so I never even knew they were available. I may have some literature on it that I'll post if I can find it.

AndyW

My Feedback: (1)

Last two pages of Kit Bashing 1/2A Engines.

Tom @ Buzzard Bluff

Like yourself I was doing other things at the time the Hiscott system was available (wonder when & how long that actually too place?) but I've subsequently picked one up somewhere. It is very close indeed to the ideal throttle for the Cox FRV engines. Extremely well made, (have you ever looked at just the machining steps involved?[]) one is left to wonder if it wasn't likely that they simply couldn't be sold at a profit to the impecunious 1/2Aers of the day. I suspect that they would sell well today to the limited market represented on this board, but, in truth, that STILL wouldn't be enough to pay the tooling. I would cheerfully fork over $25 for the muffler alone today and count myself fortunate. Tom

AndyW

My Feedback: (1)

Tom,

Your way is superior, allowing exact alignment and also more surface area for the JB Weld. Quite doable with a round file along with care and attention to detail. The trick is getting a spring but as the throttle stop on the Norvels are just a nuisance (IMO) these can be used and are just perfect.

BTW, see if your camera has a macro feature. This allows for sharp closeups. Also, use the flash.

AndyW

My Feedback: (1)

Tom,

In retrospect, I think that the Hiscott throttle was simply way ahead of its time. With the heavy radios of the day, wing loading on 1/2A planes was such that it took full bore just to stay in the air. Today, with very light radios and coverings and much more powerful engines, a plane can be built that is full house, with throttle and ailerons and it'll perform just as well, if not superior, to the .40 stuff. I guess that's what I've been trying to preach for the last number of years and perhaps I've stated my case poorly. It's a real eye opener to take off from typical field grass, do it all and then some, land, chat with the guy next to you and then simply take off and do it all over again, without having to bend over even once.

Tom @ Buzzard Bluff

BTW, I no longer own a Queen Bee (Thank God!) but IIRC the muffler for it was a direct take-off of the Hiscott pattern. It's a shame Cox didn't carry the copy all the way and make the original exhaust restrictive aspect of the muffler functional as well. Had they done that rather than use the bad joke carb it would have been a viable product IMO. Tom

meowy84

Tom, who is the VA and also the AP distributors? Would you happen to have the contact info for either and/or idea on the prices for these respective carbs?

Tim Wiltse-RCU

meowy,

Larry Driskill carries VA's his site is www.kittingittogether.com of course he is also a member here on this forum. As for the AP throttle I think Hobby People carry it for something like $15.00

LAter,
Tim

Prawnik

Where does one get a VA engine? I haven't seen them for sale anywhere. Or should I just score one on my next trip to Russia?

Andrew

See Tim's post -- immediately above yours.

Tim Wiltse-RCU

Prawnik,

See the above post!

Later,
Tim

meowy84

I tried hobbypeople.com but they're in Finnish?*sigh*

meowy84

AndyW, I finally got a chance to finish reading your posted articles. Very informative. From what you say it seems that the best throttling is the VA....but since the original VA was discontinued do you have any experience (idle figures and reliability of the idle) with the VA MKII R/C as sold by kittingittogether.com? I see you referring to the 'new VA' which you mention idles very well at 4.5K....are you referring to the MKII? In another part of your article you say: "This particular throttle/muffler of my own design has been fitted to a stock Babe Bee .049...and once again throttling is perfect....the best bottom end is 5.5K" Which throttle is this? Can you point it out or post a pic or describe it? I would be very interested in seeing how it looks so that I may duplicate it and do some of my own experiments if that would be OK with you.

hfenn

M84
It's hobbypeople.net

meowy84

Thanks hfenn.

Ok, I found the AP .061 carb on the hobby people site for $15. Since this appears to be the primary easily-available carb what is your guys' opinion on it as a basis for some experimentation (and ease of adding air bleed, etc.)?

boberos

To Andy W.
Re post # 35

Perhaps the reason the Hiscott never got popular was the price. Mine has a $16.95 sticker on the blister pack. I mentioned it in apost here at 1/2 A a while back but no one seemed interested.

BTW, I have been using it for 2 seasons in my Top Dawg & it performs flawlessly.
Good power, good idle, & instantaneous transition.

Good luck & thanks for the excellent info.
Bob G

meowy84

Bob, what engine are you using the Hiscott carb on?

AndyW

My Feedback: (1)

M84,

Yes, I'm referring to the VA MK2. Right now it's the only 1/2A available that comes with a means to adjust the low end mixture. As such, you can get a reliable, low idle with very good transition to the top. All VAs just like Cox engines crave a castor based fuel, the more the better. Be aware that some castor/synthetic blends only have a small percentage of castor in their mix. Minimum, in my opinion, is half and half castor/synthetic. In other words, if you saw a blend that had 20% total oil, 10% castor and 10% synthetic would work. One hundred percent castor, of course, is the best fuel to use on Cox and VA.

"This particular throttle of my own design" refers to an exhaust throttle with muffler that I made to get away from the problems associated with the sleeve type restrictor. Namely loss of power at the top and the need to install a piston without SPI (sub-piston induction). Pictured is that unit which was later used to investigate differing methods of tank pressure and other elements of exhaust throttling. That something works, is fine but I'm always interested in how and why it works.

Bob,

I'm sorry I missed your post. I'll look for it right now. One feature of the Hiscott that I contemplated adding, was to make adjustable, the relationship between the intake and exhaust closure. I anticipated situations where this might be useful but, as you found, the throttle works very well as is. The Medallion carb body is somewhat restrictive and it might be useful to install a stock, VA or some other throttle to a TD body. This might liberate more power. These ideas were never tried because the Hiscott was a loaner and I didn't want to mess with it.

Tom @ Buzzard Bluff

I gotta defer to Andy on the question about modifying the Wasp carb. He is 'da man' on the subject. Frankly I wouldn't even know where to locate the airbleed passage since I see none on my Wasp. FWIW however there appears to be sufficient 'meat on the back side of the carb to mill a flat to drill & tap for an airbleed screw. I'm hoping that Andy will chime in here myself.

On a slightly different subject. I tried a 'down & dirty', 'po boy' exhaust throttle this past Summer, not unlike Andy's muffler/throttle in principle. I simply used silicone to seal an old after-market exhaust collector/muffler to a Cox cylinder and fitted an old RC carb to the outlet to act as an exhaust restriction. Unfortunately I don't keep careful records as does Andy so I am left with only general impressions to share. Even without perfect sealing in the amatuerish 'lash-up' I was able to get a dependable idle (with no other modifications) down @ 6,500 IIRC. For it to work properly good seals are a prerequisite just as with the throttle rings. FWIW, I had only modest success with throttle rings until Andy told me some years ago to find a sleeve/throttle ring combo that had an interference fit and lap them together, leaving the fit very tight. The change was dramatic. As he himself has pointed out several times in the case of his own work I have Cox reedies that idle so low and silently that the loudest sounds emenating from them are the noise of the prop and the clicking of the reed. It is that sort of fit that mitigates against effectiveness of the Cox muffler/throttle ring combos made from aluminum. They simply 'grow' faster than the cylinder to which they are fitted when heated.
So the 'RC carb on the exhaust pipe' as a throttle control shows promise but, once again, 'the Devil is in the details'. Fit is critical and an old carb that has a sloppy barrel just 'ain't agonna get it'.

AndyW

My Feedback: (1)

Yes, the AP throttle gives you enough "meat" in the body to add an adjustable airbleed. With the others, with the exception of the new VA and the RC .05, you have to "add the meat" with JB Weld.

The issue of course, is how do you stick it on to your favourite Norvel and JB comes to the rescue again. The stem from a Norvel throttle is glued to the bottom of the Wasp throttle with JB Weld. Pics to follow.

A note of caution. The barrel of the Wasp and Norvels are a differing diameter. All other parts are interchangeable.