There was once a thread about what activity could replace valve cover racing at the challenge. I suggested a spec hammer store drill challenge, and a few people were supportive of it, but ultimately the thread fizzled. This came up in discussions during drinking + sim racing last night again. I can no longer find the original thread, so I'm starting this one.
Here is my proposed competition:
- Construct a wheeled vehicle of some sort (bike, scooter, car, whatever) that is powered by a single spec hammer store drill (no additional power sources, no energy storage aside from battery)
- Vehicle must be operated by driver/occupant (no remote control)
- Achieve the maximum top speed possible. Either measured by radar, gps, maybe autox timing lights 100ft apart, etc.
- Drill body and internals cannot be modified (no upgraded motors or speed controllers) except:
- mounting provisions
- relocated trigger/throttle
- Battery may be modified.
- Driver must wear helmet, probably some other safety stuffs.
2 classes
Small block:
Big block:
I just need to know how much distance I have to get to my top speed so I can figure out gearing. Thank you.
Yes!!!
requisite number of wheels? I think 2 would greatly simplify things and expand the potential starting points, but also if one of y'all manages to get into actual speed, maybe there's a bigger safety concern?
I would probably vote in favor of spec battery too, but I may be in the minority here
4 wheels means more weight but if speeds get much over 20mph maybe there's an advantage to lower CoG and possibly aero. So much science!
*edit:
Thinking on it more, I think two wheels has way more potential. Possibly mandate leathers and boots, maybe skid plates.
Looking on HF website, looks like the 20v has a max tq of 450in/lb and max 450-1700rpm through an "all metal gear construction" what looks to be a two speed selector.
*double edit.
If the spec sheet is accurate, and we assume 450in/lb @ 450rpm = 3.2hp. I'm sure it isn't that simple, something about peak electric tq being at very low rpm. Still, I seem to remember my 3hp go kart would do 20mph. There's real potential here.
oh this would be fun as e36m3
Is rupturing and igniting the battery pack for propulsion legal?
Do I have a time limit to complete my run?
"Battery may be modified"
Are we gonna learn the voltage required to make a bauer drill weld itself into a brick?
I thought "battery may be modified"
just meant that you could buy the "bare tool", and then get the 3Ah or 5Ah instead of the "1.5Ah kit" battery? (assuming 'Big Block')
or is someone going to get ambitious and try to hack this to run multiples in series/parallel?
Robbie (Forum Supporter) said:
"Battery may be modified"
Are we gonna learn the voltage required to make a bauer drill weld itself into a brick?
Really depends on how many runs we are getting/required to verify top speed and how many spare batteries we are allowed.
In reply to sleepyhead the buffalo :
Fairly easy to build/hack these battery packs to pretty much any desired voltage. We may run into issues in the internals of the spec drills before the batteries are forced into hazmat fodder. My FIL has a cordless drill he made a horrid battery for, the thing gets HOT, but so far it's still chooching. IIRC he's running it somewhere around 26/28v.
Oh, it's on.
edit: these things are surprisingly heavy.
I'm learning already.
Apparently DC motors don't have so much of a torque curve as a torque line. Mostly linear, the closer you get to max rpm, the less torque, until basically zero.
So 450rpm max (assuming max tq is rated at the lower gear setting). And HP is a function of rpm, figuring something in the middle is the best compromise. ***.8hp/18.7tq @ 225rpm. If direct drive on 20" bicycle wheel, we have a theoretical top speed of 13mph. I bet we can double that.
***fixed. Sorry for the bad math.
So, there are a couple factors at play:
For brushed DC motors, the torque vs speed on paper is a linear relationship interpolated between the stall torque (torque at 0 speed) and No Load Speed (max speed at 0 torque load). Realistically there are a few factors at play including the efficiency of the motor as well as the abilities of the batteries to provide peak current to the motor over time as they both heat up and discharge.
Brushless motors have a torque "curve" that is flatter out from the stall condition, then drops off linearly at a certain speed, enabling them to provide more average power with the same stall torque and no load speed. They are also more efficient.
At the end of the day, your motor is going to cap out on speed wherever the torque reaches equilibrium with the drag loads of your machine. Depending on the mass and length of the course, the goal will be to achieve the highest average speed based on balancing your ability to accelerate up to that speed with increasing the top speed your machine is capable of.
Tentatively, I'm in for 2024.
Can the drill be utilized to wind a mechanism, spin a flywheel, or otherwise impart some energy that does not directly go to the wheels?
In reply to ¯\_(ツ)_/¯ :
Why would you ask this? This is how you win and you ruined it.
In reply to nocones :
You of all people should know that the magic is in the execution of the absurd hypothetical creation.
¯\_(ツ)_/¯ said:
Can the drill be utilized to wind a mechanism, spin a flywheel, or otherwise impart some energy that does not directly go to the wheels?
I, for one, would be happy to see what you would come up with as a method for dumping more of the battery's potential energy during the course of the run, provided the resulting kinetic energy is somehow contained. Don't need any more Violet Rule incidents...
I did math. In low gear (max 450rpm) power never exceeds .8hp. But that peak is with over 20ft/lb. In the higher gear, we get up to .7hp, but at only 3.75tq. A clear disadvantage.
I don't know what increasing voltage does to tq. But I can't imagine it'll make any of those numbers go down. Do with that what you will.
So - who's getting on the bike with a large garage door spring popping and creaking with potential energy under the seat?
What we really need are competition specs.
Because we have the AutoX timing system (?), how about setting the start/finish up 100'(?) feet apart and either use a standing start or allow a 20' (again ?) run up zone. To make it interesting, no wheel # requirements? Fastest time wins honors, a free flashlight, and a new 18V, or 20V battery, depending on class. $5 entry fee (to cover the new batteries, maybe).
And I think we are going to need more clarification on what is allowed, battery wise.
I'm up for additional entry fee for the class. I would ask for the drag strip for the runs. Should be plenty of space to hit any speed possible, and built in traps to record it. I'll volunteer to make the trophy. Fairly sure I'll have a drill I can paint gold and mount, as I'm sure I'll roach at least one during testing.
In reply to barefootcyborg5000 :
I honestly think the drag strip will be too sticky.
If potential energy is allowed we need to limit battery capacity somehow or someone will find a way to harness a megaton of TNT worth of energy into a spring on a drill-powered-vehicle the size of a 737 given enough staging time.
barefootcyborg5000 said:
If the spec sheet is accurate, and we assume 450in/lb @ 450rpm = 3.2hp. I'm sure it isn't that simple, something about peak electric tq being at very low rpm. Still, I seem to remember my 3hp go kart would do 20mph. There's real potential here.
This is not accurate math - that 450lb-in is the stall torque in low gear. 1700 rpm is the free speed in high gear. You can't get that torque at that speed. It's probably more like 100-150W, not 2200W.
