Who's got a Gearbox on their O/B?

[Kris Flynn]

Hey All

i just wanted to find out who on this board runs an F1 style O/B Tunnel Hull with a gearbox? i am interested in what one you are using and how good it is, speed and durability wise?

or if someone runs an F1 style o/b tunnel hull on 7 cells, what setup they are using

Thanks
Kris

[pmpjohn]

Belt drive, 1.3-1,Astro 6 turn 05, 12 cell, Octura X642.

[Kris Flynn]

Hey
very fast indeed ;) do you have to do much maintenance on that 05 while its running on 12 cells?
would you happen to have any pictures of what the belt drive setup looks like, i would like to know how its done :)

Thanks
Kris

[pmpjohn]

Very little maintainance on the Astro at the 12 cell level. Flush out the comm and brushes and a little oil on the bearings. I think all the hype these days is about brushless and nobody remembers what a powerhouse the Astro cobalts really are. Magnets that would take an oxyacetaline rig to damage and silver brushes that wear like iron. The only failures I ever had was from over proping and burning wires or on some of the really old motors before the kevlar wrap,throwing comm segments.
I do not have any detail pics of the outboard on my PC but there is a construction article I did for RC Boat Modeler in the Sept 91 issue. The hull construction is covered in the Jan 92 issue. Full size hull plans are available from RC Boat modeler #FSPB11911.
If you can not find the back issues E mail me your snail mail address and I'll send you some old literature.

John

[Kris Flynn]

John

sent you mail...

it definately looks like its flyin!! thats what i want my tunnel to look like on 7 cells :P
do you still have this awsome little Tunnel? around what speed d you think you were getting with the setup you had...do you think its the best it could have done?

Kris

[pmpjohn]

Kris,
We had his boat on radar at 37 mph. The hull is very light, framed with 1/8 balsa and planked with 1/32 ply on the bottom and 1/64 ply on the top. This was fast enough at the time to win two APBA national championships 90 & 91. Top speed can be a little higher with a 5 turn Astro 05 or a 5 turn Astro 25 direct drive but at the cost of run time. A race was 5 laps and I liked to have 6 laps of run available in case dumb thumbs required a penalty lap. No points for a DNF.
Yes I still have a couple of these hulls around, sorry not for sale.

[Kris Flynn]

DAMM thats fast, for an electric tunnel :D
can wait for that stuff, even though it will take awhile i cant wait ;)

what O/B leg did you use for the belt drive? are the hulls you have lying around setup to run, or just the hulls...im in the process of designing a hull (580mm long) which will be build from 3mm balsa frames and still deciding on what to cover it with, either 1.5mm balsa or thin ply... i will run it on 7-8 cells and will hopefully FLY like yous is in the pic :D

Kris

[Andrew Gilchrist]

John

What happened to the Warehouse Hobbies version of your tunnel?

I have an ABS version that won a few races in '98

Andrew Gilchrist
fastelectrics.com

[pmpjohn]

Andrew,
You have one of five or six vac formed hulls that ever left the factory ! I still have all the hull tooling. The problem has been with the investment casting molds for the outboard lower unit. We ordered fifty sets of castings from the foundry and every one of them was warped to badly to use. I haven't found any of the plastic lower units that I felt were heavy duty enough for reliable long term duty at this power level. The other side of the story is convincing Tony to invest $Ks in tooling that could take years to break even on. If you know of a lower unit you think might work let me in on it. Keep in mind that during my testing and racing I never ever had a lower unit failure. The only time I broke a belt was when a 24 cell Astro 40 with belt overdrive prototype snagged a floating baggie.

John

[Kris Flynn]

John, what lower unit was used when setting the records? or what one is on it at the moment?
bit of a shame that this boat didnt get much more exposure...it looks pretty good and seemed to go well too

Kris

[pmpjohn]

I started out using modified K&B 3.5 nitro lower units. After a while I had tooling made for my own investment cast aluminium lower units. Unfortunatly these are the molds that no longer seem to be able to make a straight part.

[Andrew Gilchrist]

John

I will stay in touch re the leg - you never know ;-)

I must ssay that tunnel runs real sweet very light and fast even on 8 cells it is a ball!

[Kris Flynn]

Hey

my Cousin is a pattern maker, and im thinking of asking him if he would be able to make an outboard leg, that is similar to the kyosho, but would be better quality and maybe be just made from CF...do you think this would be very hard for him to do?

Kris