Building Tips and technical articles. > ARF'S
New Vector 40 ARF
Allen Eshleman:
There are a bunch of ARF and ARC Vectors at Brodaks. These will probably be the last ones.
Geoff Goodworth:
I have two early ARC Vector 40s.
If the engine bay in the later examples is the same as my early ones, there is an issue with the length of the LA 46 and FP 40 — their length is such that you must use a spinner with a recessed back, like the Dubro design.
If you want to use a spinner like the Brodak design, you need to fill the gap between the nose ring and the back edge of the spinner.
The majority of LA 46s used at our club have run best on the 6.75mm ID venturi that came with early FP 35s and FP 40s. The best running FP40s have all used the stock FP 20/25 venturi (6.55mm ID). Since the 6.75mm venturi has been unavailable for years — unless you know somebody with some spares — I have simply used a reamer to open up the 20/25 venturi and not made any alteration to the rest of the throat since the increase is fairly small.
I think there are plenty of Vectors flying with Brodak 40s which are shorter than the FP and LA and lighter.
Don't forget that if you have a need to extend flight time, the addition of a bit of acetone and a reduction in the nitro will help.
Acetone is an old speedway riders' trick that was reflected in Shell A. The data sheet used to say there was 3–5% hydrocarbon depending on the season. A former work colleague of mine — who was Australian Speedway Masters Champion about 15 years ago — was surprised that we modellers were not fully familiar with the use of acetone. He said that it was very commonly used in speedway — especially on cold nights.
Dan McEntee:
--- Quote from: Geoff Goodworth on June 19, 2022, 07:33:58 PM ---I have two early ARC Vector 40s.
If the engine bay in the later examples is the same as my early ones, there is an issue with the length of the LA 46 and FP 40 — their length is such that you must use a spinner with a recessed back, like the Dubro design.
If you want to use a spinner like the Brodak design, you need to fill the gap between the nose ring and the back edge of the spinner.
The majority of LA 46s used at our club have run best on the 6.75mm ID venturi that came with early FP 35s and FP 40s. The best running FP40s have all used the stock FP 20/25 venturi (6.55mm ID). Since the 6.75mm venturi has been unavailable for years — unless you know somebody with some spares — I have simply used a reamer to open up the 20/25 venturi and not made any alteration to the rest of the throat since the increase is fairly small.
I think there are plenty of Vectors flying with Brodak 40s which are shorter than the FP and LA and lighter.
Don't forget that if you have a need to extend flight time, the addition of a bit of acetone and a reduction in the nitro will help.
Acetone is an old speedway riders' trick that was reflected in Shell A. The data sheet used to say there was 3–5% hydrocarbon depending on the season. A former work colleague of mine — who was Australian Speedway Masters Champion about 15 years ago — was surprised that we modellers were not fully familiar with the use of acetone. He said that it was very commonly used in speedway — especially on cold nights.
--- End quote ---
A good portion of the guys reading this probably don't know what speedway racing is!! The ones in Southern California may, if there are any left there!! Bruce Penhall was a typical southern Cal blonde headed beach kid the took to the sport and eventually became world champion. There is supposed to be a cinder track somewhere in Indiana but I have never found any information on it. Search the engine section a bit, I know acetone has been mentioned as an additive before but I forget what ailment it was supposed to cure. Around these parts, to extend run time, Coleman lantern fuel is usually added to the regular fuel mix. Anything that will blend in and burn should do the trick. All it is doing is taking up some space of the methanol, so you have to lean out the needle to get the same RPM, and thus a longer run time.
Type at you later,
Dan McEntee
Dave Hull:
If you are going to try to fit the Sullivan 6 oz. tank, get the flexible one. It will let you squeeze the "overflow vent bubble" along the fuselage side. As far as length, that's going to be tight, too. My Vectarf has some major nose mods (bulkhead moved forward, etc.) but it looks like from where the bulkhead used to be, you would have to get the neck and tubes thru it. A slant tank might help? I am running the Sullivan 4 oz. RST but so far have been using the Evo .36 and OS .35FX. One of our club members has just started flying a Vectarf with an OS .46LA (he won't run anything else....) so I could ask him what he's got for a tank if that helps.
To Geoff's and Dan's comments on doctoring fuel with acetone for range extension--and speedway:
https://www.facebook.com/SCFTARacing/photos/gm.704385087320532/7838189396193026/
There are tracks at Costa Mesa, Perris, Bakersfield and Ventura here in SoCal.
Dan McEntee:
--- Quote from: Dave Hull on June 21, 2022, 08:51:55 PM ---If you are going to try to fit the Sullivan 6 oz. tank, get the flexible one. It will let you squeeze the "overflow vent bubble" along the fuselage side. As far as length, that's going to be tight, too. My Vectarf has some major nose mods (bulkhead moved forward, etc.) but it looks like from where the bulkhead used to be, you would have to get the neck and tubes thru it. A slant tank might help? I am running the Sullivan 4 oz. RST but so far have been using the Evo .36 and OS .35FX. One of our club members has just started flying a Vectarf with an OS .46LA (he won't run anything else....) so I could ask him what he's got for a tank if that helps.
To Geoff's and Dan's comments on doctoring fuel with acetone for range extension--and speedway:
https://www.facebook.com/SCFTARacing/photos/gm.704385087320532/7838189396193026/
There are tracks at Costa Mesa, Perris, Bakersfield and Ventura here in SoCal.
--- End quote ---
There is a difference between Speedway racing and typical flat track racing. The biggest difference is that Speedway bikes are very light weight, have no brakes what so ever, are a purpose built bike with a single cylinder engine around 500cc's, single speed transmission and dry clutch. They often burn straight nitro methane. Wheels and tires are much thinner than what are seen on those in the picture that the link take you to. Races are usually four lap sprint races that can be quite exciting. Slowing the bikes down for the turns is accomplished by pitching the bike sideways and controlling the speed and direction that the bike is going with the throttle and steering. Speedway is very big in Europe where they can draw crowds approaching 10 to 20,000 people. These bikes mostly race on cinder tracks. Truly a matter of turning right to go left! Flat track is much the same, but bikes are heavier, multi speed transmission, bigger tires with rear brakes, and race on tracks ranging from 1/4 mile up to one mile ovals. Riders usually wear a steel skid shoe on their left boot to help with guiding and steering the bike in the turns, especially on short tracks. I have seen some of the top riders on mile tracks that are well groomed and prepared, manage to broad slide their bikes through the turns and not put their left foot down, and doing so can really push their speed average up considerably, near the 100mph range. An off shoot of that is what is called TT, and is on a shorter track, anywhere from 1/5 to 1/2 mile long that also has a right turn or two in it along with a shallow jump. One of the most prestigious and longest running dirt track races in the country is the Peoria TT held at a club track near Peoria, Il. It has been held for something like 75 years or more. For a good movie that explains these with some fantastic video and camera work, you MUST see the classic "On Any Sunday" by Bruce Brown. The follow up movie follows the pursuit of a world championship in Speedway by Bruce Penhall, who cut his teeth racing motorcycles in southern California.
Type at you later,
Dan McEntee
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