speedmd wrote: ↑
Dec 16 2021 10:11am
Nice torque curve on the TXT 300. Very strong off the bottom. Looks like it was not yet jetted proper to make power as observed above the 6200 rpm break in the power plot. Overall looks to be a great power plant for the class. Unfortunately, with the limitations of the piston engine, it mostly relies on the clutch when you need a more sudden jolt of energy.
Looking forward to your electric build developments. Electric should be able to add a whole new level of performance to the sport.
Trials ICE engines are so focused on the low end of the power curve that it'll be more than jetting causing that power dip I reckon - long intake tracts, super long exhaust headers, almost no tuned resonance exhaust, tiny carb bodies for throttle response at low RPM ...
I increasingly stick to the belief that there's nothing unfortunate about needing a clutch. A clutch and flywheel are an elegant and efficient solution to a range of problems, particularly relevant to trials. In some ways I think it's the old hammer and nail analogy - "if you have a hammer, everything looks like a nail". Just because you might be able to achieve a similar result electronically doesn't necessarily make it "better". And at the moment no-one has come even close to being able to do electronically all that a flywheel/clutch combo can do.
It's a significant challenge to electronically create a device that:
- provides "inertia" to roll up an obstacle with absolutely no chance of the wheel spinning up if it loses traction for a moment
- enables instant cut to that "inertia"
- provides instant power with both hands in positions of strength on the handlebars (twisting the throttle down is incredibly difficult to do when you're jumping up with your hips coming right to the bars!)
- allows for very fine and fast control of power delivery (our index fingers are significantly more sensitive and accurate than moving our whole hand/wrist). This is in conjunction with the item above - try to finely and accurately control a throttle whilst jumping through the bars! ROFL. Way better to build up some stored power, then control it with a nice stable index finger.
- Smooths out accidental throttle impulses due to rough terrain, but provides instant power response when wanted.
Here's links to two videos. This is a technique fully reliant on instant on/off power.
First is an ICE bike doing a "front on". Carefully watch clutch, brake and throttle and you'll see how precise the timing of all this is (this guy is 2 times Australian Champ, 18 x West Aust champ, used to ride Worlds & Euros etc.) The interval between the clutch lever starting to move out and starting to move back in is 1 second! The interval between clutch starting to move out and the tyre leaving the ground is under 0.75 second.
Second is an electric trials bike with clutch doing the same technique.
I've never seen anyone on an electric bike without clutch do this (could be I just haven't looked in the right places).
The sequence for this is roughly:
Build RPM (inertia) with front brake locked and back wheel held in place (usually with slipping clutch, but could be brake if you're coordinated enough)
Rapidly pull hips/torso forward and up.
As you extend into the "up", but just before full extension, release clutch & brake, close throttle; pretty much all at the same time.
Pull the bike up with the bars as it accelerates, but let it jump ahead of you.
Land on the back wheel, cut power, balance and manage exit off the top.
I cannot imagine how you could do this with just a throttle for most of the reasons in the list above.
Certainly on my unclutched e-trials it is a complete joke trying to do this (I can do it competently on modest obstacles on an ICE bike), the ramp up of power is just waaaay too sloooow, and this bike is pretty quick off the bottom being specifically designed for trials.
Clutch/flywheel combos are pretty good devices I reckon!