Rattling front mudguard Sprint 7

[electric.mike]

brake judder the thoughts of an ignoramus

my powabyke had brake judder when i first got it, i retuned it to the dealer he fitted better quality blocks and adjusted the toe in, the break judder vanished but it returned after 40/50miles, so i decided the best way to deal with it was to avoid using my front break first, this improves things.
but on looking at the problem the toe in cant stay the same on the wear surface for long,one section of pad must be always doing more work as it hits the wheel first.
so my questions are, do the long pads that are in use now make any difference compared with the short pads we used to have on steel rims,are the breaks just too efficient,is it made worse by the straight forks instead of the curved forward ones.
if toe in and new pads temporarily solve the problem`this would be whilst the breaks are bedding in so are less efficient,as soon as they get efficient the problem returns.
i have never had break judder from the back i guess because the break is inefficient and there is a lot of weight over the wheel.
mike

edit anybody tried fitting the brake behind the front fork to make the brake unit itself more rigid (i know daft idea)

 

[flecc]

That's right Mike, in part the inefficiency of a rear brake means the wheel locks before judder point is reached. The other factor is that the single legs of front forks have more flexibility to vibrate and enhance the judder.

The fork angle isn't relevant. You'll shortly see the Tour de France bikes setting off from London this year and be able to note the near vertical fork angle on those. They wouldn't be able to tolerate any judder given the need to brake from 60 mph or so right down to a relative crawl for hairpin bends on the Alpine downhill sections.

The problem appeared mainly with the introduction of alloy rims, necessitating soft pads to avoid excessive rim wear. That soft rubber material flexes and springs, just what's needed to either commence a judder or worsen it. Prior to that with steel rims we had brake BLOCKS, referred to that way since they were very solid and had no flex in them. That, combined with the shiny chrome surface of steel rims meant not many judder problems, and in the dry they were great brakes. Unfortunately, in the wet they became NO brakes, hence the eventual adoption of alloy rims which have a consistent though rather average performance in both wet and dry. Initially they also used hard blocks, but after some horrific accidents involving rims exploding apart at speed downhill when brake block heat further weakened the worn thin rims, a change to soft pads was necessary.
.

 

[Ian]

Shimano Deore XT V-Brake on Torq - Still Judders

Well, Ive now done 41 miles with the Shimano front brake and the judder is no better than with the original Tekro, the braking effectiveness is much improved so I'll be leaving the Shimano brake on. incidentally, The NiMh battery I'm currently using has just gone to red but the bike is still going. It was last charged when I fitted the brakes 41 miles ago! And Ive been up some pretty steep hills to test the brakes on the way down. Who needs lithium

I'm now resigned to having to live with the judder, it 's still a mystery why it doesn't affect all users equally though.

 

[nigel]

Nigel

BY Ian
I'm now resigned to having to live with the judder, it 's still a mystery why it doesn't affect all users equally though.
Well Ian you gave it a try i dont think any forum members hand on heart really know what causes it apart from EZEE i think its a combination of factors 28 wheel front motor wheel rims i suppose if this was a car it would have been sorted out as it is we still got a rear roller brake that works NIGEL

 

[rsscott]

I had quite severe judder when I received my Torq. The problem though was caused by the headset not being set correctly. Once that had been adjusted and tightened, the problem disappeared. Plus mine has the original brakes that contribute to the juddering problem.

 

[flecc]

Mine is completely original and has never juddered, but the 20" wheel Quando with the same Tektro/Diacompe brake set up juddered like mad. After improving it with both Clarke MTB and Avid 20R pads, Shimano cartridge pads eventually almost completely cured it.
.

 

[ITSPETEINIT]

TORQ Motor noises

I'm just going by my first motor which started doing this and gradually started destroying itself. As long as it doesn't start locking up in reverse you'll be ok Peter. I understand it's a rare fault though.
.

from:
Technology Explained: the Brushless Motor

Pictured in the animation is a conventional 4-pole brushless DC Motor. It consists of four magnets shown as yellow and blue arcs that are affixed to a rotor hub which in turn rotates in the center of the stator. The stator is depicted in the animation by the gray concentric circles with six "teeth" pointing inward toward the rotor. The stator consists of a stack of stamped, thin metal laminations. Once they have been stacked and insulated, magnet wire is wound around each of the six teeth. Electrically, this motor is conventionally known as a "Y" winding and is a three-phase design.

In this illustration Hall-Effect generators are used to sense the position of the rotor and are indicated by the three devices that are separated 120° apart and which change from black to red depending on their state.

The day before yesterday I was very worried about the 'noises off'. Yesterday, it was quieter and today 'almost sweet' - just the pulses, no grinding or vibration noises.
I have done some logical (not scientific) analysis of this noise which I have previously described as 'like a mudguard stay rubbing'.
I analysed the rotary criteria of the motor, having the suspicion that this 'PULSE' was in sync. with motor revolutions. At 15 mph there are (a fiendish calculation) 2.91 revs. per second. I counted (as best I could without losing concentration on the road and it's homicidal potholes) and found that there were 39 pulses in 15 seconds (might have missed a few - they come up quickly and remorselessly - and the potholes ).
SO! I have concluded that these pulses are in sync. with the 3 devices referred to in red above.
NOW! Does this indicate 'well being' in the motor? Or is it a symptom of something to which more consideration should be given?
The human mind, being what it is, one is never quite sure where imagination leaves off and reality begins. On the day before yesterday, when the noises were very disturbing, I imagined (or did I ?) that they became worse when the battery (Li) was three quarters discharged and the gradient had steepened to about 6%.

Why am I so paranoid? Paranoia is in direct proportion to the cost of replacement!!
Peter

 

[ITSPETEINIT]

More on Brake Judder - Torq and Sprint

It wont go away - neither the judder nor the concern.

I have done some more analysis, although accuracy is hard to come by.
I had previously commented that even when, after scrupulously cleaning the rims and blocks, there remained an 'of/off' sensation when applying the brakes hard.
This led me to wonder about the consistent width of the rim over the full circle of one revolution.
Armed with my digital calliper, which measures down to 1/100th mm I adjusted the front brake of both bikes so that in the slackest position on the rim the wheel would just move without binding (NOT rubbing I stress). On the Torq, in three positions on the rim, about 12 inches apart the width of the rim (appeared to be) 24.56 mm where there was considerable binding. In the slackest position the width of the rim (appeared to be) 24.11 mm.
On the Sprint the maximum width (appeared to be) 24.51 mm and the minimum (appeared to be) 24.32 mm.
I wonder what the manufacturing tolerances of width are for my rims -
Torq: Weinmann XTB24 - ETRTO 622X20
Sprint: Weinmann ZAC2000 - ETRTO 559X19
Or is a difference of 0.45 mm and 0.19 mm considered acceptable, producing no ill effects?
Peter

PS I dont recall having 'kerbed' either rim nor having bottomed out the tyres notwithstanding the 'homicidal potholes' i have encountered but steered around, much to the consternation of following car drivers.

 

[Ian]

At 15 mph there are (a fiendish calculation) 2.91 revs. per second. I counted (as best I could without losing concentration on the road and it's homicidal potholes) and found that there were 39 pulses in 15 seconds (might have missed a few - they come up quickly and remorselessly - and the potholes ).
SO! I have concluded that these pulses are in sync. with the 3 devices referred to in red above.

Peter, don't forget there is gearing between the the motor proper and the wheel so the motor will be doing very much more than 2.91 revs per sec at 15 mph. It is perfectly normal to feel the pulses as the windings switch on and off at very low speeds, but if you are hearing 2-3 noises per second at 15 mph then I would suggest the cause lies elsewhere.

Also don't forget that the motor that Flecc had problems with is of a different design. The motor currently used in the Sprint is a well proven reliable design.

Yesterday I noticed a noise occurring once per revolution of the cranks. Was the bottom bracket about to disintegrate or had I bashed the chainwheel? A certain amount of paranoia had set in before I discovered the noise was friction between the outer and inner parts of my shorts .

On the subject of brake judder, my Torq brakes juddered all day ysterday right up to the point where I juddered to a stop outside my back door. The bike was put away but apart from a battery change was not touched until this morning when I did 3 short journeys totalling about 10 miles without a trace of judder. Work that one out!

 

[flecc]

My Quando had a front rim with a wide spot at the join Peter.

Rims are made from continuous channel extrusions, cut to length and wound around a former, then welded. Some unevenness is inevitable with this process.

As Ian remarked, the hub is internally geared down, typically by about 7 to 1 on a 26" wheel with a Hall effect motor.
.

 

[ITSPETEINIT]

To Clarify - it's the Torq motor

As Ian remarked, the hub is internally geared down, typically by about 7 to 1 on a 26" wheel with a Hall effect motor.
.

The question concerning brake judder on both the Torq and the Sprint have muddied the water (it may have been me in an earlier post that "stired" it).

The three pulses I get from each revolution of the Torq Wheel (like a mudguard rubbing)are what concerns me with any problem the Torq motor may be having at this time
Peter

 

[Ian]

With all the bikes between us there's plenty of scope for confusion Peter.
However the Torq hub motor is also geared down, not sure of the exact ratio but 6:1 or thereabouts rings a bell.

 

[flecc]

There are three orbital gear wheels Peter, so it seems there may be an aberration like a tooth blemish on the orbital toothed gear ring in the hub shell, which each orbital gear wheel can strike once in a wheel revolution.

It's impossible for me to judge at a distance if this is a serious noise or minor, so I can only suggest you keep it under observation and act if it worsens considerably. If it is a tooth fault, they usually develop very rapidly, so if it doesn't worsen or just fluctuates, it's probably going to be ok.

If you scroll down on this page you'll see the gear wheels.
.

 

[ITSPETEINIT]

Orbital gear wheels in Torq Motor

There are three orbital gear wheels Peter, so it seems there may be an aberration like a tooth blemish on the orbital toothed gear ring in the hub shell, which each orbital gear wheel can strike once in a wheel revolution.

It's impossible for me to judge at a distance if this is a serious noise or minor, so I can only suggest you keep it under observation and act if it worsens considerably. If it is a tooth fault, they usually develop very rapidly, so if it doesn't worsen or just fluctuates, it's probably going to be ok.

If you scroll down on this page you'll see the gear wheels.
.

Ah,ha! Now that is what I can understand as a logical explanation of what I am hearing (even if it's not the case of a belmish on the O.G. Ring).
A peek inside might clarify/clear the matter up: BUT not by me!
The O.G.Ring looks like its metal, and the 3 orbital gears nylon.

If the nylon orbital gears revolve 3 times for each revolution around the orbital gear ring that would give a 'pulse' of 3 times per wheel revolution. The motor gearing of 6:1 (or whatever) is the relationship between the geared shaft and the combined effect of the ratio of that to O.G.Wheels and their ratio to O.G.Ring. (you can see who/what you are dealing with here )
I recall that it was not 6:1 (per Ian's post above yours Flecc) but a higher ratio: I forget where to find it in the exponentially growing Forum. It looks like, from the webpage photos, about 9:1.
Therefore it is less likely to be an abberation of a damaged tooth on the Geared shaft or one of the O.G.Wheels: most likely the O.G. Ring. (I'm thinking aloud here so that it can be shot down).
Seems strange to me that it would then be the harder metal gear ring that got damaged: perhaps something embedded between two teeth? That might eventually damage all three nylon O.G.Wheels, but still give 3 pulses per wheel revolution.
I've got a window of about 10 days to decide on my course of action - the next time I could go to Loughborough.
Peter

 

[coops]

Hi Pete

I'm not shooting, honest helps to think out loud, I know, so I'm just doing likewise here now

Been examining these matters myself lately: seems the Torq motor speed after internal gearing is about 260-280ish rpm at max revs and under load, if derestricted (restricted, about 2/3 of that).

Two observations: the maximum wheel spin speed of 260-280 rpm is not reached till about 23mph under load or 27-28 mph unloaded, so usually the wheel spin rate is less than that. Secondly, if the pulses were caused by gear ring trouble, wouldn't their frequency vary with the voltage the motor is at i.e. the throttle setting, rather than being constant at 3 per second?

Hope thats helpful Pete

Stuart.

 

[ITSPETEINIT]

Pulsing from Torq Motor

Hi Pete

I'm not shooting, honest helps to think out loud, I know, so I'm just doing likewise here now

Been examining these matters myself lately: seems the Torq motor speed after internal gearing is about 260-280ish rpm at max revs and under load, if derestricted (restricted, about 2/3 of that).

Two observations: the maximum wheel spin speed of 260-280 rpm is not reached till about 23mph under load or 27-28 mph unloaded, so usually the wheel spin rate is less than that. Secondly, if the pulses were caused by gear ring trouble, wouldn't their frequency vary with the voltage the motor is at i.e. the throttle setting, rather than being constant at 3 per second?

Hope thats helpful Pete

Stuart.

Hello Coops:
When I said that there were (about) 3 pulses per second I was making the judgement on a speed of 15 mph (the maximum restricted speed of the Torq). Of course with less throttle, there would be lower voltage and thus lower speed (on the level) and lower wheel rpm.
What it also another mystery (apologies for not mentioning it earlier on my posts on the subject) is that when the front wheel is lifted off the ground and the motor is run there are no audible (to my poor hearing) pulses at all.
I don't think it's three stones lodged in the tyre
Peter

 

[coops]

Ok yes, Pete, sorry for not re-reading the earlier post more fully, you did say about 3 per second at 15 mph.

In that case (sorry again if its stating the obvious!) but wouldn't 3 times per second be more or less exactly the rotation rate of the Torq tyre at 15mph? (roughly: 15mph = 6.94 m/s, wheel is 2.23m round (maybe less, if you have m+ now?) so 6.94/2.23 = about 3.1 revs per second...)

So maybe one stone in your tyre, eh?!

 

[ITSPETEINIT]

There's Maths and Damned Maths

Ok yes, Pete, sorry for not re-reading the earlier post more fully, you did say about 3 per second at 15 mph.

In that case (sorry again if its stating the obvious!) but wouldn't 3 times per second be more or less exactly the rotation rate of the Torq tyre at 15mph? (roughly: 15mph = 6.94 m/s, wheel is 2.23m round (maybe less, if you have m+ now?) so 6.94/2.23 = about 3.1 revs per second...)

So maybe one stone in your tyre, eh?!

Yeah, Coops, You're right, of course.
What's that Cliche? "This is doin' my 'ead in!"
It had better not be a tack. They are new Marathon Pluses I've put on 40 miles ago. Perhaps it's a 'Persian Soldier' caught up in there? Or a long distance runner!
Peter

 

[coops]

hey, many heads are better than one and we can always do the maths between us - it all adds up in the end - is this a new form of "distributed computing" ?! Anyhow, its still better than statistics (as in lies, darned lies and....). Talking of which, now it seems it may be a wheel/tyre issue, don't overlook that you have two tyres that could be the source of the pulses

Stuart.

 

[ITSPETEINIT]

Problem Solved

hey, many heads are better than one and we can always do the maths between us - it all adds up in the end - is this a new form of "distributed computing" ?! Anyhow, its still better than statistics (as in lies, darned lies and....). Talking of which, now it seems it may be a wheel/tyre issue, don't overlook that you have two tyres that could be the source of the pulses

Stuart.

I've never found my TWO heads much use when it comes to Maths.
I've solved the problem of the pulsing front wheel: Pheidippedes said I had got a 'Persian Soldier' stuck under the valve in the front tyre when the Marathons were fitted causing a tramping noise. big grin - (Coops used up all the smiley quota - see above)
The high pitched mechanical noise when accelertaing from 0 - 8 mph is, I've been told, normal.
When it's running at 10+ to 15.5 mph the motor is ' as sweet as a nut'.
The rattling front 'guard is solved by keeping both hands on the bars.
The Sprint 7 goes like a dream - over hill (10% or 11%) and dale.
Thank you everybody for your input. Together we covered lots of ground with a steep learning curve thrown in for good measure.
Peter