Photo Journal

[TimD]

Ian,

I thought about doing that but was told they are not durable enough in our sort of application. I was also thinking of making a mechanically shifted 'box instead of a centrifugal type. Have the two different ratio's fairly close so the motor stay's on the pipe for the shift without inducing too much bad behavior, and use the 1st gear for launch only.

Weight would be the big disadvantage plus it goes against the KISS principle.

What do you think?

Tim.

 

[Ian Inverarity]

Joe,

PIP, they make the A100 I have pics of in the other post. The design is not right tho, I have had a lot of problems and it is out of service at the moment. Sounded good tho!

Tim

The cars use glass reinforced moulded gears which are probably more durable than delrin, plus the cars bounce around and put a lot of cyclic load on the gears. I used to have a BMT on road 1/8 scale just for fun, the gears went onto a plain 5mm shaft and lasted as long as I had the car. The shift was very positive, it was not a centrifugal clutch, but a centrifugal pawl which hit a pin, so the shift was sudden and positive. Using the clutch bell on the motor would be bad, it would get wet, slip, and burn out. The biggest problem I saw was teh ratios would be wrong, the prop shaft would be two slow.

I would not try to build a shifting gearbox, that sounds like to much work! The BMT box was really simple tho, which is what got me thinking. I dont have the car anymore tho, and I dont run 21's in oval anyway!

Actually you can probably get the same effect as a gearbox using a variable length pipe. I have a bunch of Maximisers, 21, 45 and 67 to try one day. They allow you to change pipe length by 25mm from the radio! I have not tried any yet, I think I need to fix the leakage on them first.

Ian.

 

[_laxmasta2039]

Tim,

i like the tim tabs on the geared mono....that's neat how they're bent down at the ends to act kinda like mini turn fins....did you do that yourself??

 

[Ozzy]

Tim the boat is already registard it is the Miller High Life ;D ;D

 

[TimD]

O.K.

The hull is a VERY heavy Carbon fibre 21 hull made here in Australia. The boat was our "dyno" and is pretty battle scarred. The hardware in it is all scratch built. The trim tabs / turn fins are 1 piece (easy to make from some angle aluminium). The gear drive unit is very quiet thanks to the delrin gear and runs at 1.6 to 1 underdrive. This allows the boat to use very large prop's - like the prather 250. The tuned pipe is very very short. The motor is pulling well in excess of 30krpm.

Ian, your statement about variable pipe length being a substitute is close but goes away from why we went with gears. The main reason for me building a geared unit is for the reason that gear reduction is a torque multiplier! And if there is one thing a 21 needs - it's more torque!

This boat was converted to gears purely as an experiment. I am 100% sure that if I built a boat specifically for the gear drive (a rigger) that it would be super fast. (riggers can handle lot's of pitch on the prop's - not so good on a mono with a small rudder blade )

 

[Propjockey]

I can "hear the gears turning" from here! Were you looking for another project? ;D

(maybe we can keep up with the electrics after all!)

 

[Ian Inverarity]

Tim,

I meant using the variable pipe length for a substitute for shifting gears, not as a substitute for a gear drive.

As far as I know the main benefits of gear drives come from lower prop shaft speed giving less friction and allows the use of larger and more efficient props. These must be considerable advantages as gear train losses would not trivial. For 67's and larger the benefits have not been found to outweigh the dowsides, at least in multi racing in europe.

I have seen various discussions on Dave Marles site, it seems that gear drive riggers have not been successful. I am not sure why tho, maybe the extra weight and higher CG caused problems. But 21 and 45 gear drive monos are very popular over there.

Ian.

 

[Propjockey]

Hey Hammer-I'm a step ahead of you in regards to getting kids interested.

Here's my daughter's 'Wee Vee' -Mabuchi 540 on seven Nicads

 

[Propjockey]

Still needs paint, but she has fun with it.

Check out that custom rudder! Hacked it out of an aluminum clipboard--high tech stuff!!

 

[TomMoorehouse]

well it was fun..... but i cleaned up the thread as requested :

 

[MikeP]

Ok, more boat pictures ;D.

Here is my scratch built "Wildthing" electric.

 

[MikeP]

More boat pictures. Home brew .15 rigger.

 

[MikeP]

One more... Sport 20 Dumas Pay-N-Pack with Grimracing cowl.

 

[Ron Olson]

Somebody likes small-block motors! I'd bet John Finch would love to see the picture of the electric Wild Thing. I like your innovation on the rudder setup. My son wants me to build him one of those Sport 20's but then He'd like to have about every boat ever made. We need to kick IMPBA's rear in gear to get a Nationwide class going for them.

 

[Ian Inverarity]

My old style Kingcraft with Zenoah G23 at the 2001 Aust Nationals. This boat did okay for me, I won 5 out of seven races and set fastest heat time. The orange is fluro and the photo does not do it justice! Note on the deck the emergency fuel cap (a rubber foot for a chair!!!)

I could not fit a boat stand on the plane.....

Ian.

 

[Ian Inverarity]

After the above boat was driven over by a Volvo (not kidding! > ) I transferred the hardware to a newer style Kingcraft. I sold this boat a few months ago.

Ian.

 

[Hammerhead]

What's up with this. Nitrocrazed's cool pics got wiped out :'(.

It also takes forever to open.

Hammer