Yamaha YZ250F

[j bjork]

There has turned up a bunch of pictures from "ränneslättsloppet", I have some that I have bought:



Dont know, somewhere on the track..



Coming down from "the mountain". It dosent look like anything in the picture, but it is a decent drop going from the rock down on the gravel. I think the ktm behind me with his leg down is one of the riders going in front of me up the mountain on the second lap. We went different paths up. Then he came in to "my" path in front of me before going down, but stopped at the drop, so I had to go around him and take a worse track





It was very dry, with a few exceptions. This is after the mountain, I think maybe they tried watering down the mountain to make it more difficult, but the water ended up here.



I dont know where this is, but it looks pretty cool

 

[j bjork]

As I havent really got the printing of flexibles working yet, I decided to have a go at PETG.
I mean, how often do you break a plastic bottle?

First I tried a brake line guide:

Turned out alright I think, some stringing but not too bad.
Ehum, the color might not be the best match to the rest of the bike

Then I did the brake disc guard:

Oh my god

 

[harrisonpatm]

Oh my god

Is that your reaction because you like it? Because it turned out well? Or just because the color is so shocking?

 

[j bjork]

Is that your reaction because you like it? Because it turned out well? Or just because the color is so shocking?

The color, it was the first time I printed PETG and I already had this roll. I didnt want to buy another before testing it.
Not sure why I bought this one, but I suppose I thought it could be an interesting color in some circumstances

Here are some other pictures with different techniques to go down the mountain at ränneslätt:




There are some that jump out too, I prefer to just drive right out and pretend to not be scared/to know what you are doing.
It has worked so far

 

[j bjork]

Last ride I came home with this:

I run tubes in my practice wheels, mousse in the race wheels.
I thought it was a pinch flat, as I had been at a rocky track. But it turned out to be the valve that had ripped partly out of the tube.
Anyway, I decided it was time for this:

I have hesitated as I have some used tires to run, and I was worried they will leak.
I guess I will see, the air is still there after a day at least

 

[72V]

My guess is you're experiencing heat creep, with TPU already being as soft as it is. heat can transfer from your print nozzle up through the filament allowing it to bunch up and jam in the extruder. But to answer your question regarding different brands of filament working better than others, absolutely! I have had drastic differences in print quality and failures between different brands. For the most part, you can get any of them to work well with enough tuning, but it takes time to get some filaments dialed in. Try SunLu if you haven't already, I think they have great performing filaments and they aren't that expensive either.

I have been running tubes in the practice wheels and saved the expensive mousses for race lately.
But now I think it was time for new mousses and tires, and get rid of my cut up tubes for extended life

In the rear the tube was broken

Interesting to see how the mousse has shaped itself after the tube.

New all black sidepanels too, I planned to change them before "stångebroslaget" (as I should have black background and white numbers) but didnt get them in time..
Now it is the same thing for "ränneslättsloppet", so I change them now instead.
I didnt plan to participate this year, but was persuaded.
It is like 20km of rocks and whoops, then maybe 2km with just whoops but no rocks.
You sure come out "shaken not stirred"
It was also this crazy queuing for more than half the first lap, with over 700 starting at the same time.
But this year they have changed it, so it will be more like 250 in my start.
I did some research in the TPU matter. 95A seems to be the most common hardness, and also the stiffest of the more common ones. Therefore also the most likely to succeed on my ender 3 printer.
I got a rather expensive roll locally (the only one I could find locally), but I am having rather limited success.

I have been able to print a calibration cube rather successfully. It is relatively soft, but with a more plastic than rubbery surface.
But when I try to print my discguard it jams after about 2 layers.

I tried changing from 0.4mm to 0.6mm nozzle, but it didnt help.
Maybe I should get one or 2 other brands and see if they print easier?
From what I have seen on youtube it seems like they can vary pretty much even when they are supposed to be the same hardness.

 

[72V]

Well, the 30mm/s still failed on layer2. It got a little longer than the previous ones though.
I raised temp to 245degrees, turned off part cooling and turned off retraction.
That print didnt even make first layer, so maybe as you say it can be a problem that it is too hot.
I lowered to 225 and the same thing again, didnt make first layer.

24hours for a seat? Sounds really fast compared to how long my prints usually take.
With these settings this print should take 22hours, I think it was 9hours with 50mm/s.

Here is the extruder, there is a screw in each end of the spring. But they are not connected to anything adjusting, they are just securing the spring in place.

The whole system, I have a ball bearing spool holder with a strait feed line to the extruder.

If you want faster prints and better overall print quality look into the Bamabu line of printer. They have quickly become the industry standard for in-home printing. They produce excellent quality prints, including multi-material prints if you get the AMS to go with it. Not to mention they easily print 2x - 3x faster than your ender, they have automatic bed leveling and can print exotic materials such as carbon fiber. And most importantly they just always work. No messing around with bed leveling, and fixing clogged extruders, etc. its more of an appliance for someone who just wants to make good quality parts as opposed to a hobby machine that constantly needs attention.

 

[j bjork]

Thanks, I decided to do a smaller update on my ender 3 v2 with another extruder and a smaller steppermotor mounted as direct drive. Maybe later I get another printer. It has been discussed in this thread: Ender 3 v2, upgrade or not?

The petg discguard died today:

The front mount broke off, and I suppose the rest of it broke when it was pushed in to the brake disc.
I think I will make another ABS one for now, then have another go at flexible when I have updated the printer.

Oh, the red tire looking thing in the previous post is a tubeliss insert for the rear wheel. I see that it wasent very clear in the post
I have been running it now for two practices, it feels weird at first until you get used to it. You can kind of feel the tire "climb", I dont know how to describe it in English. I have pretty low tire pressure now 0,3 bar. Maybe I should raise it a little.

 

[Chalo]

"Already been chewed" materials are usually a letdown, I find. I wouldn't use filament 3D printed parts for anything I wouldn't trust to papier-maché or oven hardening PVC clay.

 

[scianiac]

The problem with PETG in all my testing and experience is while it has high tensile strength and good layer bonding, it has terrible impact resistance and tends to go through brittle fracture exactly like what you showed. I never got around to calibrating my IZOD impact tester so I don't have exact numbers, only relative numbers but PLA is crap, "tough" PLA is slightly better, PETG is about as good as tough PLA, ABS is vastly better horizontal and vastly better vertical when printed in ideal layer bonding parameters, which is low layer height, wide extrusion, maxed fill ratio and hot (250-260C) at 70C chamber.

Impact and durability wise ABS is still not as good as some more exotic filaments but some of those can be much hard to keep that strength across layers. Horizontal, Nylons, TPUs, and good PC as well as alloys of those will beat it but most are hard to get good impact performance in the vertical.

I think you should try either a carbon fiber nylon which generally has quite good printability and decent mechanical properties. And wait for it to absorb moisture from the air before you go stressing it. Much less warping issues than pure nylon so cooler chamber should be OK.

Possibly a PCABS, which will have very good horiztonal impact but vertical will be a challenge.

Or a Nylon-TPU alloy, which now that Taulman was murdered by incompetent Brazilians the options for are limited but just recently I think I found a source for some here. Now I have not yet tested that brand so I have no idea how it will perform but the old taulman stuff prints like nylon generally but has better layer bonding, is pretty stiff so I think it will print fine in a bowden extruder, prints feel about as stiff as soft nylon, but layer bonding is extremely good. Impact wise it will pretty much beat anything, like just stops the IZOD hammer dead.

PC really you need a hot chamber and layer bonding is very hard, also impact performance is good but only horizontal due to layer bonding and only if it's high quality PC, cheap PC seems to be pretty meh impact wise, the Lexan stuff is very good though.

 

[72V]

The problem with PETG in all my testing and experience is while it has high tensile strength and good layer bonding, it has terrible impact resistance and tends to go through brittle fracture exactly like what you showed. I never got around to calibrating my IZOD impact tester so I don't have exact numbers, only relative numbers but PLA is crap, "tough" PLA is slightly better, PETG is about as good as tough PLA, ABS is vastly better horizontal and vastly better vertical when printed in ideal layer bonding parameters, which is low layer height, wide extrusion, maxed fill ratio and hot (250-260C) at 70C chamber.

Impact and durability wise ABS is still not as good as some more exotic filaments but some of those can be much hard to keep that strength across layers. Horizontal, Nylons, TPUs, and good PC as well as alloys of those will beat it but most are hard to get good impact performance in the vertical.

I think you should try either a carbon fiber nylon which generally has quite good printability and decent mechanical properties. And wait for it to absorb moisture from the air before you go stressing it. Much less warping issues than pure nylon so cooler chamber should be OK.

Possibly a PCABS, which will have very good horiztonal impact but vertical will be a challenge.

Or a Nylon-TPU alloy, which now that Taulman was murdered by incompetent Brazilians the options for are limited but just recently I think I found a source for some here. Now I have not yet tested that brand so I have no idea how it will perform but the old taulman stuff prints like nylon generally but has better layer bonding, is pretty stiff so I think it will print fine in a bowden extruder, prints feel about as stiff as soft nylon, but layer bonding is extremely good. Impact wise it will pretty much beat anything, like just stops the IZOD hammer dead.

PC really you need a hot chamber and layer bonding is very hard, also impact performance is good but only horizontal due to layer bonding and only if it's high quality PC, cheap PC seems to be pretty meh impact wise, the Lexan stuff is very good though.

You should check out CNC Kitchen on YouTube, he has a great video showing the strength of different filaments compared to each other. I was shocked to see how durable PLA is compared to PETG and ASA in some of his testing. I think PC (Polycarbonate) would be the best material for the chain guard or any part that needs high-impact resistance. However, as mentioned above this requires a chamber heater. With that said, I designed and sell a chamber heater for Bambu P1S and X1C printers if anyone is interested. It (could also be used for other printers with a closed chamber). This is a must for printing PC. Pic attached.

 

[j bjork]

I have watched a bunch of his videos
Mostly some time ago, so for sure it wouldnt hurt to watch some of them again.

I recently had a look at the primary chain, I didnt see any note that I have checked since I changed the chain.
I probably had, there was almost no slack. I tensioned it a little anyway.

Finally I did something about the kickstand.
It had developed a significant play and would rub against the swing arm.
It was expensive when I bought it, and seems to be even worse now.
So I ended up making a bronze sleeve.
I didnt have the proper tools, but it seems like it turned out alright.
Time will tell

We had a club championship last weekend.
First there was a shorter qualifying lap, and I managed to qualify top 10
That meant I got to start in the first line, in a silent start
I never had this opportunity before. In all other races I have either started a few lines back, or you have to run to bike, or stand behind the bike.
So I thought this is my chance, Im giving it all I got

I took the start, kind of expected that.. But I didnt expect I was able to hold first place all the field and like 4 turns or something in the track. I made a mistake soon after and lost two more positions, but after a while it got silent behind me.
(And those three that passed me are really fast, like top riders in their classes in big races.)
It turned out there was a nasty crash behind me, and a rider got picked up by the ambulance.
He turned out to be ok after some check ups luckily.

I will continue another time, need to get something done too..

 

[j bjork]

I dont know if anyone is interested to read these long stories in bad English, but here you go:
After the crash the race was called off, I came in at forth place as almost nobody behind me continued after the crash.

It was unclear if there would be a restart, but we could practice on a part of the track in the meantime.
I did, and it was good practice as the track had just been smoothed and it had been raining. Making it a little tricky, as it can suddenly be soft in some parts and things like that.

It turned out that there would be a restart, I misunderstood the starter a little and didnt make as good a start as the time before and was almost caught up by the fastest rider. He did pass later on, and also the second fastest.
But I did hold 3:d, and I think I even had some distance. But I need to check what he who was behind thinks. Anyway, after a few km something happened and I hit the ground.

I got up and straightened the bark busters decently and tried to take off, but the bike wouldent run
It just jerked like when there was a connection problem with the motor position sensor.
I tried to fiddle with the wires but it didnt help, I had to give up

 

[A-DamW]

I dont know if anyone is interested to read these long stories in bad English

I am!

 

[harrisonpatm]

I am!

Me too

 

[j bjork]

When got up to speed the bike would run fine. And often very suddenly from stuttering badly to taking off at 3/4 throttle or something, almost throwing me off. I got back to the pit, and then the bike ran just fine again off course
After a wash, still fine.
I opened up the wiring and pulled on the wires with no problem. But eventually when pouring water on the joints and at the same time pressing them together or against the frame I was able to recreate the problem, and do the same thing a few more times for confirmation.
Very annoying to have a problem with the same wiring again, but at least better than if it was the controller or motor.

I used shrink tube with glue the last time, but I suppose it wasent enough.
The wires have a hard, slippery surface. That dosent help I suppose.

What I did this time is use "press and melt" joints. I suppose it is the same sort of hot glue as the shrink tube, but these are transparent so you can see that there are no air or anything like that.
I also spread out these joints and made new wires all the way to the controller.
I put a shrink tube over this and filled up with silicone sealant (RTV).
I was hoping that when heating the shrink tube it would press the silicone everywhere inside, but the shrink force was a bit weak.
It filled out in both ends at least. This is getting ridiculous, I really hope it works this time

Lately I have been kicking or kneeing the handlebar protector when hitting the ground.
This time it really broke.

This one is from the new bike, the yz450f. I was tempted to take it, but decided not to. I'm trying to avoid starting to pick off parts
I will check what a new one would cost, and decide if I should buy one or try to print in flexible material.

 

[j bjork]

Did a double this weekend, a rocky and hilly track yesterday and my clubs hometrack today.
The track today is the one I ride the most, and it was rather wet today.
No problems with the bike, and I hit a new personal record today

Well, actually I think I broke it three times. The fastest I had been that I know of is 16.20.
Now I hit 16.08, 15.45 and 15.32

 

[j bjork]

I have finally been able to print a tpu discguard:

Just to find it is too soft, when mounted it feels more like a mudflap than something that take some of the impact when hitting rocks

My regen brake thumb throttle has getting stuck rather easy lately when it is mud or wet sand on the track.
I decided to see if I could so something. It was rather dirty and the surfaces where it glides were scratched.
I cleaned it a little and tried to put some extra tension on the return spring.

I shortened it maybe 25mm, but it turned out it got too small and would jam halfway when pressing the lever.

I ended up just changing it, and trying another model this time.

 

[j bjork]

Got a double flat today, that has to be an achievement of sorts

 

[j bjork]

It has been a hard weekend again
I was at a pretty tough track yesterday, it is long (12-13km) with a lot of rocks and mountains.
It also has some extreme enduro trails, that you can get to from the main trail.
I did pretty mush of both, 4 laps on the main track and 3 laps on two of the extreme trails, and 2 laps on two other extreme trails.
I got so bad cramps afterwards..

Then today it was "stubbrace" after harvest on the fields they set up a track.
It was often pretty tight racing were you tried not to loose the one in front of you, and definitely not get passed by the one behind you.
I have a log from the final that might be interesting to some here:

Mosfet temp, I suppose the motor temp curve looks similar.

Another one, without zooming.

If Im reading this correctly it is about 43kW@5500rpm

Around 400bA and 45kW seems to be what I get, I am not sure what is limiting.
Battery voltage sags pretty bad, but not enough to limit I think.
Maybe rpm/sec acceleration, I havent got around to change and see.
Very few times that I have been able to use more power, possibly never

 

[scianiac]

So in that last image, your set phase current limit is well above 813 and your battery current limit is above 438 and your battery voltage start is set below 107V and no temp limits are reached and you're at WOT? If all of those are true then the phase current theoretically should be higher because the duty cycle should be higher but I and others have seen sometimes VESC just won't push the duty cycle high enough to maintain the phase current in that range. Not sure exactly why, could be some undiscovered bug or something. I experienced it badly but mine was either caused for exacerbated by poor current measurement hardware and noise. Like in the 2nd to last image you can see the duty cycle is basically at max (95%) so a lower phase current is to be expected as the BEMF is limiting your current but in theory it should be able to keep it at the phase current limit up to the point that duty cycle hits 90-95%, at least from my understanding.

 

[j bjork]

It seems max duty is set to 95%

I think the max temp on the controller was about 50 degrees and motor about 70 degrees,
so there shouldn't be a problem with that.

No power limitation.

Voltage shouldn't be a problem either from what I can see.

It looks like 1000pA is the limit, but that is just the program.
It is set to 1200pA

I cant say for sure that I was at wot at that particular moment, but I was sometimes.
The other peaks dosent seem to be higher, but I will have another look.

There are logs of a lot of strange stuff, but they didnt seem to think throttle position were relevant
To show the reason if there is a limit would also be interesting I think..

 

[Dui ni shuo de dui]

"Already been chewed" materials are usually a letdown, I find. I wouldn't use filament 3D printed parts for anything I wouldn't trust to papier-maché or oven hardening PVC clay.

That's true. Except for TPU, this thing is unbreakable especially if you print it with a large diameter nozzle.

 

[PK2000]

I love this build because you thrash it until it (or you) breaks, fix the problem and repeat... Hats off to you sir!

 

[j bjork]

Thanks, I used to mess with cars.. Then it was more broken car parts and less body-parts
It is built to be ridden, and I am trying to test its limits.
It is quite capable, so it is usually my limits that is tested