Specialized Big Hit FSR with midmount

Sharp shooting Simon!! I have a really nice BSA airsporter S in the cupboard, guess its all about compressed air and not springs these days though :)

There is some good riding in Derby for sure! I need to get an off roader sorted out as my BMX isnt man enough for that :lol: I have a nice frame already just need to get the motor in it, Cro mo mid mount with a custom frame would be mental!! ha ha I know you dont like the weight in the wheel so its the only option for you maybe? although if you are going to go that way then maybe just a big motor like a Lemco or Etek might be better? controllers are cheaper too! and the controllers that are available have better throttle settings.

I would be up for a meet, lets do a north and south meet! keep everyone happy :D if we start it...they will come :wink: #fieldofdreams
 
lostrack said:
I tell you what guys...

DON'T STAND UP!

the reason you can't use a fast pickup motor for mountainbiking at the moment, is the power is so instant, you can't stand up while riding it.

I tried it on my 3220 RC setup (dialled down to 160 amps) and it threw all my weight to the back, which then made me turn the throttle more (think : the angle of your hand on the grip!). It's a real struggle NOT to flip over. Brakes VS motor are pretty well matched, so you need real control to keep it on track.

The only way I found to do this, was to sit down on the saddle - and who does this when riding a MTB on a downhill course?

I have a speed throttle which is rediculously twitchy. The RC CA setup may help
Click to expand...

yep, its called whiskey throttle, happens on powerful dirt bikes, highly amusing, its when you get thrown back from a small throttle input, and as you fall back your hand grabs more throttle from the extra twist, and your off the back before you can say "gee that throttle is touchy".

that kona vid could not be a better example of it, very enjoyable to watch :twisted: also see the poor dude who ends up shoeless on the ground with lukes agni bike, a hv160 rc controller seems to be a key ingredient in for quality gravel rash. -we do want halls and good modulation from the controller and ill admit we dont allways get this, but rc stuff meant for planes without current control do seem a little "touchy".

but honestly guys, if you only believe one thing i say: torque throttle is what we need.

you know how it goes, the first millimeter of throttle (with all our "normal" speed based throttle controllers) gives you absolute full power, untill you get to say 10kph, then that sudden take up is the second mm of throttle, at near full road speed the first 90% of your throttle does nothing and the sudden take up happens in the last mm of throttle and at no point do you get good smooth control, its a drama on any of these high torque machines, and we are just not used to it cos all (petrol) engines are not like this.

you need to chose the torque you want with your hand, its what is natural for us so we are in precise control of how much we get thrown back, if you watch that kona stinky vid you will see this clearly, torque throttle is how we can have 5, 10 or 20 times this power level under some level of control with ic engines, and why these machines can be so bitey regardless of what type of brushless motor we are using. was it you tench haveing a go at the torque throttle a while back?
 
Kepler said:
So How does a torque throttle actually control torque? Our do you mean Current throttle?
Click to expand...

yep, current based throttle, rather than speed, when we all use speed based (cos our controlers happen to be that way) with grunty setups then you touch the throttle a tiny bit (requesting say only 10kph)
and you get flipped straight off the back as the motor gives its all to blast you from a standstill to that speed without remorse, watch the kona vid for a refresher and be sure to pause on the graised arm for the end result.

that kona could well become a very nicely behaved gentle AND powerful machine (our controllers are meant to be in "control" of our motors, as they have precise position feedback many samples for every single rotation) and i dont think more weight or a throttle delay is what your after? not when we should have better control of the motor than any other machine around (stepper motors and servo motors like for a cnc lathes are not much different to all our brushless motors)

do try and give this just a little thought people, it will help move us all forward -dont make luke have to roll up here and explain how sweet and gentle his 80?kw bike is at low speed yet 10 times the power to flip you if desired, with an excellent controller setup. :lol:

theres a circuit somewhere here that was "fetchers current based throttle" or similar that i cant seem to find it yet.

the minuet the machine easily has the power to blow you off the back on take off, this problem wants looking at, and i figure we are all heading that way, and as a rider
it seems better to have a say in the matter of torque, cos some days you just dont feel like laying down behind your bike, other times (like trials stuff) you need good control of that massive launch to climb stuff.
 
I totally agree that there is massive room for improvement on the throttle's control over the motors output, it must be remembered though that the motor cycle with 150+bhp that is very easy to control has a lot of differences, at low rpm the gas engine makes very little power so is easier to control than it would be trying to pull away with it at the red line, full throttle at 2000rpm does not result in 150bhp trying to kill you, an electric motor has all its torque available all the time, maybe an rpm based amps limit in addition to the throttle could create a power curve more like we are used to with ice?

I have tried the CA current throttle setup, it was a little abrupt and only fitted to a modest cyclone so from that it would be hard to tell if there was a worth while improvement over a throttle connected directly to the controller, i should try that again with a higher power setup to feel the difference, allthough while typeing this i have had an idea :idea: :D
 
I have built some seriously fast bikes myself. My yellow trike in twin motor guise ran 0 to 70 in 4 seconds consistantly (as long as I was on fresh pavement for decent hook). It has a voltage based throttle. Yet, it was docile to drive if care was taken. I have no problem with voltage based throttles. I think much of the difficulty is the componentry used in the throttle.

One thing I do not like about current based throttles is the amount of throttle jockeying required to maintain speed in varying gradients. I live in a hilly area. I love approaching a hill at a given throttle and watching the bike maintain constant speed up the hill without added input. A current based throttle requires additional input (alot of input) to maintain speed up a hill. Of course, that is preference, however. A current based throttle maintains a constant draw which should be a bit better for longer range. So, they do have their merrits. I just want people to know voltage based throttles are not inferior, just different and, if setup properly (and controller setup properly), they are docile too.

Matt
 
recumpence said:
I have built some seriously fast bikes myself. My yellow trike in twin motor guise ran 0 to 70 in 4 seconds consistantly (as long as I was on fresh pavement for decent hook). It has a voltage based throttle. Yet, it was docile to drive if care was taken. I have no problem with voltage based throttles. I think much of the difficulty is the componentry used in the throttle.

One thing I do not like about current based throttles is the amount of throttle jockeying required to maintain speed in varying gradients. I live in a hilly area. I love approaching a hill at a given throttle and watching the bike maintain constant speed up the hill without added input. A current based throttle requires additional input (alot of input) to maintain speed up a hill. Of course, that is preference, however. A current based throttle maintains a constant draw which should be a bit better for longer range. So, they do have their merrits. I just want people to know voltage based throttles are not inferior, just different and, if setup properly (and controller setup properly), they are docile too.

Matt
Click to expand...

Matt - I think your setup has significantly more stability as the likelihood of wheelies is non existent. Plus, your body position relative to your grip rarely changes.

I agree that speed throttles aren't necessarily a problem, but when you're not riding on the flat (ie a Dirt trail), and have to change your body position for balance, the throttles respond incredibly fast, which can be a dangerous thing.

Most of my power comes on in a 3-4 O'clock range, maybe my throttle isn't calibrated.

I'm eager to give the current throttle a try too.

Matt - when you do your 0-70kph, are you flat out on the throttle, or do you ease it up? Does it make a difference?
 
Actually it was 70mph (110kph).

I would pedal twice to get the trike rolling and nail the throttle. :)

You are correct about hand position while standing off road. That is a good point.

Matt
 
Whiskey throttle is exactly the reason i went from full grip, to half grip to thumb throttle, which imho is the best type if your going to be bouncing about over rougher terrain, never had a unexpected blip with thumb.
In fairness i had a thumb throttle in the crash vid and the reason for the 8kw spike in its response was a combo of many things including settings on the controller and an incompatability with a current limiter which was for another rsc, oh and a serious lack of skill :lol: - still just goes to show what can happen if you havent even done a wheel off ground test before you go out - should have heeded Pauls warning!! :mrgreen:

D
 
recumpence said:
Actually it was 70mph (110kph).

I would pedal twice to get the trike rolling and nail the throttle. :)

You are correct about hand position while standing off road. That is a good point.

Matt
Click to expand...

Sick. You got 70? How did this go unnoticed?
 
0 to 110kph in 4 seconds is incredibly quick (do link us up with the info if you could recumpence, i missed that too) but yes lostrack that is well spotted, you cant really whiskey throttle a recumbent or a car, as you dont tend fall back and add more..
when, like you say you can just nail the throttle after 2 pedals, and 4 seconds later your merrily doing 110kph, then its clear you are not suffering from the affliction. :wink:
-good point also with the thumb throttle, they do seem to help.
 
Well, it's my birthday in a couple days and a Big Hit FSR came up on Craigslist for a good price. So now I own one. The nice thing about Tench's build is it takes the pressure off. The Big Hit Mona Lisa has already been painted, so I will be content to do a clean rear hub install and an Oatnet-style fork mount battery pack. Let the fun begin!
 
toolman2 said:
0 to 110kph in 4 seconds is incredibly quick (do link us up with the info if you could recumpence, i missed that too) but yes lostrack that is well spotted, you cant really whiskey throttle a recumbent or a car, as you dont tend fall back and add more..
when, like you say you can just nail the throttle after 2 pedals, and 4 seconds later your merrily doing 110kph, then its clear you are not suffering from the affliction. :wink:
-good point also with the thumb throttle, they do seem to help.
Click to expand...

This was achieved with two 4 turn Delta 3220 Astro motors. Each pulled a peak of 400 amps for two of those 4 seconds. So, 43 volts at 800 amps. It pulled so freaking hard that I found myself yelling each time I accellerated at that rate. I finally went down to a single motor in Wye termination because it was just too fast and way too tempting. It was also unreliable in that guise.

Anyway, I am hyjacking Tench's thread. Back on topic. :)

Matt
 
Dont worry about it Matt, we are all gobsmacked by some of your achievements and never tire of hearing more about them!

I dont know enough about the electrickery side of things yet to start pushing the boundaries so i am sticking to the mechanical engineering side of it for the time being.
There are so many motors, controllers and possible configurations that i am going to ride this bike through the summer to learn and give plenty of thought to how i shall do the next one, it will probably be another over winter build like this one was only i will try to be a bit more creative with a frame from scratch next time rather than trying to fit within the confines of an existing frame. A V3 CA will hopefully be available for that one.
 
Stunning is an understatement.....makes my Commencal build look real agricultural..... :lol: :lol: :lol: :lol:

All the best.
Tony
 
Martin, now stop reading this and get back to work, i need those parts ! :D

When they are ready i will bring the bike with me so you can have a go!
 
A very nice build indeed Tench :wink:
Not only are you top of the table in shooting, your also very high in the rankings of the best bike builds/builders on ES. Some people just have no end of talent :mrgreen:

One small complaint! I see this on a lot of bike builds of various designs, and your bike (though stunning) falls into line with the others? Everyone takes great care and attention to detail - postioning motors/cnc-ing all there lovely shiny bits and bobs/securing all there wiring and batteries in a stealth like battery compartment. Then they go and plonk a controller on the down tube??? ---Wide open to all the elements. This is one thing that really bugs me :x Grrrrr
P1000072.jpg

This is ok if you live in a dry climate but even then you never know when the next monsoons going to strike. With a little CF extension you could shield/conceal your controller a bit better, you could even cut slotted vents into the CF for air flow/cooling and have an orange (colour of bike) piece of fine mesh set behind the vents for that peekaboo :oops: bit of styling.

If this is what you hit us with on your first build I cant wait to see what you come up with next...? Probably some tyre shredding thing of beauty that looks like it just fell off of the back of the starship enterprise :mrgreen:

Best of luck and fingers crossed for your upcomming shoot rounds.

Regards
Tom

PS....I and a few other members are still awaiting your wiring diagrams/battery charging setup tutorial with plenty pictures :wink:
 
Most controllers are pretty well sealed. I think that is a fine place for it. Keeping it exposed to rushing air will keep the contoller happy. Covering it up only creates thermal issues. Easy enough to add silicone sealant to any wire exit. I leave all my controllers exposed this way. Exposed wire or not having a drip loop is more problematic but heat is what will do your contoller in most of the time.
 
I have to agree with Kfong, I was caught in a total downpour with my controller right in front of the rear tire, it was flooded with water and was fine since I sealed it up with silicone...
 
I agree. Controllers need cooling hence being out in the open. Just make sure they are sealed up, and you'll be fine.

I have ridden 3 winters daily to and from work, no issues having my controller out in the open.
 
+1 on keeping it exposed... ive ridden through creeks, in the rain, yada yada etc etc. no probs for the controller. Mine hasn't been specially sealed either other than the 'water catch' area formed by mounting it upside-down on the down tube. a good drip loop helps too.

Any chance we can get some more vids of this bike in action? its kind of the Lamborghini of the ES bikes right now... and we all love to hear that engine purrrrr.... or rather..._______........ :wink:

edit
that's supposed to be silence. but its kinda hard to type the sound of silence :p .
 
sn0wchyld said:
+1 on keeping it exposed... ive ridden through creeks, in the rain, yada yada etc etc. no probs for the controller. Mine hasn't been specially sealed either other than the 'water catch' area formed by mounting it upside-down on the down tube. a good drip loop helps too.

Any chance we can get some more vids of this bike in action? its kind of the Lamborghini of the ES bikes right now... and we all love to hear that engine purrrrr.... or rather..._______........ :wink:

edit
that's supposed to be silence. but its kinda hard to type the sound of silence :p .
Click to expand...



AGREED!! Lets see it climb something steep!
 
I will see if i can get someone to film me climbing a few things on it over the weekend if i can.
 
hi tench is possible to show me inside your series and parallel connectors, because there look very robust just what i am after for my bike. thanks
 
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