So yesterday was a game changer day for me as I was able to experience a new form of motorsport! A friend of mine and hydroplane racer with several years experience offered to let me come out and try one of his race boats.
The day was a huge success I didn't flip, spin out, get thrown from the boat or have any major mishaps. I clocked the fastest straightaway speed of the day at 66.xx mph (only because I was the lightest driver but still).
So here's where the GRM hive mind can help. Because of the ongoing pandemic my friend and several other semi local racers can't travel from here in eastern Canada down to New England to race. They are looking to have a small race 6-12 boats to get some practice and have a fun day on the water.
Now hydroplane racing has a fairly unique starting procedure. There's generally a 5 minute gun, then boats are out in the water then a 3 minute warning. Then there is a countdown clock from 60 seconds. At 0 you want to be at full throttle within a few feet of the start line.
So here's where we are at. My friend Adam has built a 6ft tall clock with a single large hand, the hand is made out of 1/2 plywood but could be made out of foam to be lighter. The problem is he was trying to run it off a wiper motor and even with a potentiometer he can only get it down to 7rpm. Now we could put a pair of pulleys on but I figured someone here could point us towards an easy and cheap way of getting a motor set up that can run on 12v and turn at 1 rpm (with a 5% variance).
Can we go back to the part about the racing hydroplanes?
1SlowVW
HalfDork
7/19/20 10:43 a.m.
In reply to XLR99 (Forum Supporter) :
What do you want to know? I'm a noob but got sucked in when a motor came my way for cheap. The boats in the pictures both run stock Yamato outboards one is a Yamato 80 low 30hp range and 60mph capable on the smaller white and red boat. The second is a Yamato 102 with maybe 35hp and was capable of hitting 66mph with me in it however it would have been a little under competition weight).
My friend races at a few different locations in New Hampshire and Maine mainly in the south shore outboard racing association.
1SlowVW
HalfDork
7/19/20 10:55 a.m.
Here is a picture of the previously mentioned countdown clock. He have the face but are wondering how to power it.
Honsch
New Reader
7/19/20 12:50 p.m.
The easiest way is to buy a 1 rpm gearmotor.
Here's one that's easy to get.
https://www.sparkfun.com/products/12219
In reply to Honsch :
Would this have the torque to move a couple pound 2 1/2 foot long arm? Also do you just control the speed by controlling the voltage?
If you're racing for fun does it really have to be accurate on one minute sweeps, or just be close enough that everyone can run off of it?
In reply to ultraclyde (Forum Supporter) :
Close enough is probably fine, with two boats we just lined up and nailed it coming out of the first corner. But with 5-6 having a clock would make it great practice for the guys in attendance who actually race.
Take your wiper motor and gear it down 7/1. The benefit to this is you will increase torque so moving the hands should not be an issue.
Just wanted to say that everytime I see this topic I read it wrong.
Hey now, get your mind out of the gutter! 
When I was racing RC boats, we used a 1 RPM motor on the start clock. It had a pot to fine tune it and was fairly accurate. As for driving a 30" arm, we used a full length arm the diameter of the clock face and painted half of it the same white as the back of the clock. The other half was black. That way the motor never had to lift the weight of the arm. IIRC, the arm was foam board so it didn't weigh much to start with.
In reply to Stampie (FS) :
Coming in wide
In reply to Toyman01 (Moderately Supportive Dude) :
That's a great suggestion.
Stampie (FS) said:
Just wanted to say that everytime I see this topic I read it wrong.
Should I have gone with huge clocks?
In reply to 1SlowVW :
Depends on what vib you're going for. I think huge is less pretentious than giant personally.
When it hits the top of the hour, is the dong impressive?
This thread is going sideways...who would have thought all it takes to derail this place was a giant timepiece.
Trying to help get this back on track, I searched for a giant clock, but couldn't find anything that would get the job done for you. I really think that the best you can do is have an ordinary sized clock and put a big, well balanced hand on it to make it larger.
In reply to AAZCD (Forum Supporter) :
That's kind of what my googling found.
My latest thought is a power drill attached to some bicycle sprockets to knock the speed down. Used power drills are cheap and used Mountain bikes are free a lot of the time.
1SlowVW
HalfDork
7/20/20 11:02 a.m.
In reply to z31maniac :
I thought about that as well, or using a set of led spot lights as I know something similar is used in motorcycle racing. But doing it this way allows for my buddy to practice. The one above is what's used at the location in Maine he races at. Since he owns half the boats that will be in the water he can have whatever starting system he wants ( as long as the materials to build are cheap).
I think an analog clock is much easier to read at a glance. At least it was in the RC world. The exact time isn't important. Our clock wasn't marked other than 30 seconds and the last 5 second zone being in red. You just know you need to hit the start line when the clock crosses the zero mark. Our starts were 3 minutes. In that time you had to crank the boat, warm up, and get lined up for the flying start of the heat. With a analog clock and a large sweep, you could watch it out of the corner of your eye and never loose sight of the boat. With a digital, I think that would be much harder.
After doing some digging, it looks like most RC boat clubs have gone to a audio clock.
Seems like a system of sequential lights would be a great way to start a vehicular speed competition. Wonder why no one's tried it before.
