The latest in the fast moving saga of GNG mods is the possibility of a 14t to 18t adapter (minimal modification) in conjunction with the stock 120t pulley avalable from TNC Scooters et al. This will be easier on the belt and on the motor....
GNG 450 brushless Mid Drive - Primary Drive Modifications
- Thread starter Cyclebutt
- Start date
Microbatman
1 kW
flyinmonkie said:
Flyinmonkie Thanks for answering my 1st question. Much appreciated.
So we have now verified the Answer to question 1
Question 1 Answer buy the 95tooth sproket from TNTscooters.com it will fit the stock setup without the need for modification.
As you have said there has been lots of discussion about questions 2-4 this but I still have not found SPECIFIC answers to these questions.
Maybe I have missed something but I cant seem to find the answer.
Still looking for answers to questions 2-4
Best answer would be specific part#s and web links to buy the parts in questions 2 3 and 4. yes I have read the thread. Yes I know how to use google search. Yes they have been "Already discussed" but I have yet to find a part number and web link to questions 2-4. And yes I have found other belts that work with OTHER pulley and gear combinations. Thanks for your contribution to helping find the answer to question #1. Well apprectated. Not trying to start a fight or discredit your response. But I'm not giving up till I get part numbers and web links to the right belt and right bottom drive sprocket. That way I can send money and order the right parts as I do not have my own CNC shop. Just trying to make this as simple as possible for others to read and understand as most may not be as educated and experienced as you are on this subject. I have read your build thread and know that you know quite a bit about mid drive units.
So lets continue and stay on task.
95T pulley We now have the answer.
16T drive sprocket next.
Question#2 Where can we find a 16T drive sprocket?
We know you have to pull the old one off. But then what? File it down to 10mm to fit a chain gear? Dont really want to do that. Looking for a belt solution without filing. From reading the discussions about drive sprockets it looks as if there may be a possibility that the shaft may be too large to fit an off the shelf 16T drive sprocket. But the original belt is 14 going to a 16 should be no problem and not requiring filing.
So next step to answering this question is
What is the diameter of the drive sprocket shaft?
Then we can start to look for off the shelf already available economical parts. I have searched this tread using the search tool and put in the word "diameter" and the only info that I can conclude is that the shaft is >12mm.
So does anyone know the exact virgin unfiled diameter of the drive pulley shaft? That will allow me and others to start looking for a compable 16T direct fit sprocket. OR come to the conclusion that a 16T sprocket will not fit without machining the shaft into a smaller diameter.
Thanks
flyinmonkie
10 kW
microbatman...
Check the gng thread. Belts and pulley sizes are talked about there. Several people have already done what you are trying to do. Also look at the other gng threads to see what others have done.
There is no diameter to the motor output shaft as the pulley is machined into the shaft. You can not remove it as it is all one piece of metal. The only way tot get rid of the pulley on the motor shaft is to mill or file it off.
There are no off the shelf parts for a complete refit yet. The last missing part is a sleeve adapter to go over the motor shaft pulley. That is in development at the moment as miles has stated. He said the sleeve may be an 18t pulley and that should be paired with 120t pulley from TNC Scooters. The 18t sleeve is not available yet.
Use lighteningrods adjustable plates to get rid of the belt tensioner. And I thought I clearly answered #4. Yes the chain will need to be longer is you use his adjustable plate.
I wasn't trying to be mean, it is just all of those questions have been answered and confirmed if you read through the threads. The search function in ES is crap. Use google to search. In the google search bar type what you are looking for with endless sphere after it.
The one thing I have not found anywhere is the rpm of the GNG motor at the various volatges of the Kv of the motor. That would be very helpful in determining pulley sizes for various setups. Then you could use a gear ration calculator to determine pulley sizes.
I didn't know any of this stuff before I started, but I did a lot of research and not just here on ES, but google as well.
Clay
Check the gng thread. Belts and pulley sizes are talked about there. Several people have already done what you are trying to do. Also look at the other gng threads to see what others have done.
There is no diameter to the motor output shaft as the pulley is machined into the shaft. You can not remove it as it is all one piece of metal. The only way tot get rid of the pulley on the motor shaft is to mill or file it off.
There are no off the shelf parts for a complete refit yet. The last missing part is a sleeve adapter to go over the motor shaft pulley. That is in development at the moment as miles has stated. He said the sleeve may be an 18t pulley and that should be paired with 120t pulley from TNC Scooters. The 18t sleeve is not available yet.
Use lighteningrods adjustable plates to get rid of the belt tensioner. And I thought I clearly answered #4. Yes the chain will need to be longer is you use his adjustable plate.
I wasn't trying to be mean, it is just all of those questions have been answered and confirmed if you read through the threads. The search function in ES is crap. Use google to search. In the google search bar type what you are looking for with endless sphere after it.
The one thing I have not found anywhere is the rpm of the GNG motor at the various volatges of the Kv of the motor. That would be very helpful in determining pulley sizes for various setups. Then you could use a gear ration calculator to determine pulley sizes.
I didn't know any of this stuff before I started, but I did a lot of research and not just here on ES, but google as well.
Clay
The unloaded Kv of the stock GNG motor is 67...
36V X 67 = 2412 RPM
48V X 67 = 3216 RPM
72V X 67 = 4824 RPM
36V X 67 = 2412 RPM
48V X 67 = 3216 RPM
72V X 67 = 4824 RPM
flyinmonkie
10 kW
thanks spinning
Cyclebutt
100 W
Bee has taken my shell idea and run with it.
http://endless-sphere.com/forums/viewtopic.php?f=28&t=42785&start=1470 Scroll down a bit on this page...
After he has tested different materials, we should have a cheap fix for the primary, "Primary Drive," issue. Nice going , bee! I'll take two!
http://endless-sphere.com/forums/viewtopic.php?f=28&t=42785&start=1470 Scroll down a bit on this page...
After he has tested different materials, we should have a cheap fix for the primary, "Primary Drive," issue. Nice going , bee! I'll take two!
Cyclebutt
100 W
GNG up-sprocket 0.1 by kow, based on:
// Parametric Pulley with multiple belt profiles
// by droftarts January 2012
// Based on pulleys by:
// http://www.thingiverse.com/thing:11256 by me!
// https://github.com/prusajr/PrusaMendel by Josef Prusa
// http://www.thingiverse.com/thing:3104 by GilesBathgate
// http://www.thingiverse.com/thing:2079 by nophead
// dxf tooth data from http://oem.cadregister.com/asp/PPOW_Entry.asp?company=915217&elementID=07807803/METRIC/URETH/WV0025/F
// pulley diameter checked and modelled from data at http://www.sdp-si.com/D265/HTML/D265T016.html
//GNG consts
inner_teeth = 14;
outer_teeth = 20;
// tuneable constants
retainer_ht = 1.5; // height of retainer flange over pulley, standard = 1.5
idler_ht = 5.5; // height of idler flange over pulley, standard = 1.5
pulley_t_ht = 21.0; // length of toothed part of pulley, standard = 12
pulley_b_ht = 8; // pulley base height, standard = 8. Set to same as idler_ht if you want an idler but no pulley.
pulley_b_dia = 20; // pulley base diameter, standard = 20
// ********************************
// ** Scaling tooth for good fit **
// ********************************
/* To improve fit of belt to pulley, set the following constant. Decrease or increase by 0.1mm at a time. We are modelling the *BELT* tooth here, not the tooth on the pulley. Increasing the number will *decrease* the pulley tooth size. Increasing the tooth width will also scale proportionately the tooth depth, to maintain the shape of the tooth, and increase how far into the pulley the tooth is indented. Can be negative */
additional_tooth_width_inner = -0.2; //mm
additional_tooth_width_outer = 0.2; //mm
// If you need more tooth depth than this provides, adjust the following constant. However, this will cause the shape of the tooth to change.
additional_tooth_depth = 0; //mm
// The following set the pulley diameter for a given number of teeth
HTD_5mm_pulley_dia1 = tooth_spacing (5,0.5715,inner_teeth);
HTD_5mm_pulley_dia2 = tooth_spacing (5,0.5715,outer_teeth);
// The following calls the pulley creation part, and passes the pulley diameter and tooth width to that module
//belt
//translate ([0,15, 13])
// cube([40,1,15]);
difference()
{
pulley ( "HTD 5mm" , HTD_5mm_pulley_dia2 , 2.199 , 3.781,outer_teeth,0,1,additional_tooth_width_outer);
translate ([0,0, -1])
pulley ( "HTD 5mm" , HTD_5mm_pulley_dia1 , 2.199 , 3.781,inner_teeth,0,0,additional_tooth_width_inner);
translate ([0,0, pulley_b_ht + pulley_t_ht + retainer_ht -10])
cylinder(h = 25, r1 = inner_teeth - 6, r2 = inner_teeth +4);
difference()
{
cylinder(h = 15, r1 = 30, r2 = 30);
cylinder(h = 15, r1 = 17, r2 = 17);
}
}
// Functions
function tooth_spacing(tooth_pitch,pitch_line_offset,teeth)
= (2*((teeth*tooth_pitch)/(3.14159265*2)-pitch_line_offset)) ;
// Main Module
module pulley( belt_type , pulley_OD , tooth_depth , tooth_width,teeth,retainer,idler,additional_tooth_width)
{
echo (str("Belt type = ",belt_type,"; Number of teeth = ",teeth,"; Pulley Outside Diameter = ",pulley_OD,"mm "));
tooth_distance_from_centre = sqrt( pow(pulley_OD/2,2) - pow((tooth_width+additional_tooth_width)/2,2));
tooth_width_scale = (tooth_width + additional_tooth_width ) / tooth_width;
tooth_depth_scale = ((tooth_depth + additional_tooth_depth ) / tooth_depth) ;
// ************************************************************************
// *** uncomment the following line if pulley is wider than puller base ***
// ************************************************************************
// translate ([0,0, pulley_b_ht + pulley_t_ht + retainer_ht ]) rotate ([0,180,0])
difference()
{
union()
{
//base
difference()
{
//shaft - diameter is outside diameter of pulley
translate([0,0,pulley_b_ht])
rotate ([0,0,360/(teeth*4)])
cylinder(r=pulley_OD/2,h=pulley_t_ht, $fn=teeth*4);
//teeth - cut out of shaft
for(i=[1:teeth])
rotate([0,0,i*(360/teeth)])
translate([0,-tooth_distance_from_centre,pulley_b_ht -1])
scale ([ tooth_width_scale , tooth_depth_scale , 1 ])
{
HTD_5mm();
}
}
//belt retainer / idler
if ( retainer > 0 ) {translate ([0,0, pulley_b_ht + pulley_t_ht ])
rotate_extrude($fn=teeth*4)
polygon([[0,0],[pulley_OD/2,0],[pulley_OD/2 + retainer_ht , retainer_ht],[0 , retainer_ht],[0,0]]);}
if ( idler > 0 ) {translate ([0,0, pulley_b_ht - idler_ht +5])
rotate_extrude($fn=teeth*4)
polygon([[0,0],[pulley_OD/2 + idler_ht,0],[pulley_OD/2 , idler_ht],[0 , idler_ht],[0,0]]);}
}
}
}
// Tooth profile modules
module HTD_5mm()
{
linear_extrude(height=pulley_t_ht+2) polygon([[-1.89036,-0.75],[-1.89036,0],[-1.741168,0.02669],[-1.61387,0.100806],[-1.518984,0.21342],[-1.467026,0.3556],[-1.427162,0.960967],[-1.398568,1.089602],[-1.359437,1.213531],[-1.310296,1.332296],[-1.251672,1.445441],[-1.184092,1.552509],[-1.108081,1.653042],[-1.024167,1.746585],[-0.932877,1.832681],[-0.834736,1.910872],[-0.730271,1.980701],[-0.62001,2.041713],[-0.504478,2.09345],[-0.384202,2.135455],[-0.259708,2.167271],[-0.131524,2.188443],[-0.000176,2.198511],[0.131296,2.188504],[0.259588,2.167387],[0.384174,2.135616],[0.504527,2.093648],[0.620123,2.04194],[0.730433,1.980949],[0.834934,1.911132],[0.933097,1.832945],[1.024398,1.746846],[1.108311,1.653291],[1.184308,1.552736],[1.251865,1.445639],[1.310455,1.332457],[1.359552,1.213647],[1.39863,1.089664],[1.427162,0.960967],[1.467026,0.3556],[1.518984,0.21342],[1.61387,0.100806],[1.741168,0.02669],[1.89036,0],[1.89036,-0.75]]);
}
This is the code "bee" wrote to 3D print the shell adapter:
// Parametric Pulley with multiple belt profiles
// by droftarts January 2012
// Based on pulleys by:
// http://www.thingiverse.com/thing:11256 by me!
// https://github.com/prusajr/PrusaMendel by Josef Prusa
// http://www.thingiverse.com/thing:3104 by GilesBathgate
// http://www.thingiverse.com/thing:2079 by nophead
// dxf tooth data from http://oem.cadregister.com/asp/PPOW_Entry.asp?company=915217&elementID=07807803/METRIC/URETH/WV0025/F
// pulley diameter checked and modelled from data at http://www.sdp-si.com/D265/HTML/D265T016.html
//GNG consts
inner_teeth = 14;
outer_teeth = 20;
// tuneable constants
retainer_ht = 1.5; // height of retainer flange over pulley, standard = 1.5
idler_ht = 5.5; // height of idler flange over pulley, standard = 1.5
pulley_t_ht = 21.0; // length of toothed part of pulley, standard = 12
pulley_b_ht = 8; // pulley base height, standard = 8. Set to same as idler_ht if you want an idler but no pulley.
pulley_b_dia = 20; // pulley base diameter, standard = 20
// ********************************
// ** Scaling tooth for good fit **
// ********************************
/* To improve fit of belt to pulley, set the following constant. Decrease or increase by 0.1mm at a time. We are modelling the *BELT* tooth here, not the tooth on the pulley. Increasing the number will *decrease* the pulley tooth size. Increasing the tooth width will also scale proportionately the tooth depth, to maintain the shape of the tooth, and increase how far into the pulley the tooth is indented. Can be negative */
additional_tooth_width_inner = -0.2; //mm
additional_tooth_width_outer = 0.2; //mm
// If you need more tooth depth than this provides, adjust the following constant. However, this will cause the shape of the tooth to change.
additional_tooth_depth = 0; //mm
// The following set the pulley diameter for a given number of teeth
HTD_5mm_pulley_dia1 = tooth_spacing (5,0.5715,inner_teeth);
HTD_5mm_pulley_dia2 = tooth_spacing (5,0.5715,outer_teeth);
// The following calls the pulley creation part, and passes the pulley diameter and tooth width to that module
//belt
//translate ([0,15, 13])
// cube([40,1,15]);
difference()
{
pulley ( "HTD 5mm" , HTD_5mm_pulley_dia2 , 2.199 , 3.781,outer_teeth,0,1,additional_tooth_width_outer);
translate ([0,0, -1])
pulley ( "HTD 5mm" , HTD_5mm_pulley_dia1 , 2.199 , 3.781,inner_teeth,0,0,additional_tooth_width_inner);
translate ([0,0, pulley_b_ht + pulley_t_ht + retainer_ht -10])
cylinder(h = 25, r1 = inner_teeth - 6, r2 = inner_teeth +4);
difference()
{
cylinder(h = 15, r1 = 30, r2 = 30);
cylinder(h = 15, r1 = 17, r2 = 17);
}
}
// Functions
function tooth_spacing(tooth_pitch,pitch_line_offset,teeth)
= (2*((teeth*tooth_pitch)/(3.14159265*2)-pitch_line_offset)) ;
// Main Module
module pulley( belt_type , pulley_OD , tooth_depth , tooth_width,teeth,retainer,idler,additional_tooth_width)
{
echo (str("Belt type = ",belt_type,"; Number of teeth = ",teeth,"; Pulley Outside Diameter = ",pulley_OD,"mm "));
tooth_distance_from_centre = sqrt( pow(pulley_OD/2,2) - pow((tooth_width+additional_tooth_width)/2,2));
tooth_width_scale = (tooth_width + additional_tooth_width ) / tooth_width;
tooth_depth_scale = ((tooth_depth + additional_tooth_depth ) / tooth_depth) ;
// ************************************************************************
// *** uncomment the following line if pulley is wider than puller base ***
// ************************************************************************
// translate ([0,0, pulley_b_ht + pulley_t_ht + retainer_ht ]) rotate ([0,180,0])
difference()
{
union()
{
//base
difference()
{
//shaft - diameter is outside diameter of pulley
translate([0,0,pulley_b_ht])
rotate ([0,0,360/(teeth*4)])
cylinder(r=pulley_OD/2,h=pulley_t_ht, $fn=teeth*4);
//teeth - cut out of shaft
for(i=[1:teeth])
rotate([0,0,i*(360/teeth)])
translate([0,-tooth_distance_from_centre,pulley_b_ht -1])
scale ([ tooth_width_scale , tooth_depth_scale , 1 ])
{
HTD_5mm();
}
}
//belt retainer / idler
if ( retainer > 0 ) {translate ([0,0, pulley_b_ht + pulley_t_ht ])
rotate_extrude($fn=teeth*4)
polygon([[0,0],[pulley_OD/2,0],[pulley_OD/2 + retainer_ht , retainer_ht],[0 , retainer_ht],[0,0]]);}
if ( idler > 0 ) {translate ([0,0, pulley_b_ht - idler_ht +5])
rotate_extrude($fn=teeth*4)
polygon([[0,0],[pulley_OD/2 + idler_ht,0],[pulley_OD/2 , idler_ht],[0 , idler_ht],[0,0]]);}
}
}
}
// Tooth profile modules
module HTD_5mm()
{
linear_extrude(height=pulley_t_ht+2) polygon([[-1.89036,-0.75],[-1.89036,0],[-1.741168,0.02669],[-1.61387,0.100806],[-1.518984,0.21342],[-1.467026,0.3556],[-1.427162,0.960967],[-1.398568,1.089602],[-1.359437,1.213531],[-1.310296,1.332296],[-1.251672,1.445441],[-1.184092,1.552509],[-1.108081,1.653042],[-1.024167,1.746585],[-0.932877,1.832681],[-0.834736,1.910872],[-0.730271,1.980701],[-0.62001,2.041713],[-0.504478,2.09345],[-0.384202,2.135455],[-0.259708,2.167271],[-0.131524,2.188443],[-0.000176,2.198511],[0.131296,2.188504],[0.259588,2.167387],[0.384174,2.135616],[0.504527,2.093648],[0.620123,2.04194],[0.730433,1.980949],[0.834934,1.911132],[0.933097,1.832945],[1.024398,1.746846],[1.108311,1.653291],[1.184308,1.552736],[1.251865,1.445639],[1.310455,1.332457],[1.359552,1.213647],[1.39863,1.089664],[1.427162,0.960967],[1.467026,0.3556],[1.518984,0.21342],[1.61387,0.100806],[1.741168,0.02669],[1.89036,0],[1.89036,-0.75]]);
}
This is the code "bee" wrote to 3D print the shell adapter:
Attachments
Cyclebutt
100 W
Well done, bee! we are all indebted to you, my friend.
Denisesewa
100 W
Thats pretty impressive 
, the only codes I know are the ones cited to me when I get pulled over 
, the only codes I know are the ones cited to me when I get pulled over
Cyclebutt
100 W
HA! How's the chain drive holding up? I still like your solution but am determined to save the belt, don't even intend to change the jack shaft pulley. Will run big tooth count on the cassette and see how it does, should be fine for commuting and pedal assist.
Denisesewa
100 W
Chain's doin great, no issues so far.Cyclebutt said:
speedmd
10 MW
Shopping for a 12 tooth #25 sprocket and trying to find one I can open up possibly to 1/2" bore. Most I find are 3/8" max.
justlooking
1 kW
Denisesewa how is your mod getting on ,, is it still reliable ?
im asking because in this video the motor shaft looks like it is bent ? or the bearings are worn ??
http://s1191.beta.photobucket.com/user/Denisesewa/media/002-19.mp4.html
im asking because in this video the motor shaft looks like it is bent ? or the bearings are worn ??
http://s1191.beta.photobucket.com/user/Denisesewa/media/002-19.mp4.html
bee
100 W
I think that's his idler bouncing around
justlooking
1 kW
just had another look and i think you may be right ,
Denisesewa
100 W
Yep. just the idler, the half link was a bit stiff when I first installed the chain, things have smoothed out now, also , with Lighningrods adjustable sheets the idler is no longer neccessary.
Chain conversion is holding up just fine.
Chain conversion is holding up just fine.
justlooking
1 kW
thanks Denisesewa,
im still trying to get the confidence up to file the small pully off of the motor ,
i have the parts and the adjustable plates ,, im saving for a mini lathe, but can not work out how to get the motor apart, so it looks as though i will have to go the file route when i do it
im still trying to get the confidence up to file the small pully off of the motor ,
i have the parts and the adjustable plates ,, im saving for a mini lathe, but can not work out how to get the motor apart, so it looks as though i will have to go the file route when i do it
Denisesewa
100 W
I actually have a mini lathe ( Sherline #4400 ) but find it useless for this kind of work and even though its supposed to be high quality it isnt very accurate, when I first decided to file down the shaft I went for 12mm first to see how accurate I could do it, that left me room if I felt I needed to take it to a machine shop, since it was really quite easy I just continued on to 10mm, Christlung dissasembled one of his motors, you may want to contact him for advice if you find you really need to dissasemble it.justlooking said:
justlooking
1 kW
Denisesewa said:
thanks , i was thinking of removing the shaft to put in a lathe, therefore getting it to run as true as possible,
im very weary of useing a file in case it runs out of true or even end up off center , after all we only get one chance at doing this ,,
i have thought about putting a bigger sprocket on the motor , a smaller one on the flywheel, then on the other side where the chain is ,, altering the sizes of the small freewheel sprocket, and the size of the crank sprocket ,
with a bigget sprocket on the motor shaft, we should be able to get one to fit straight over the splined bit ,,
but im terrible at maths so can not work out a combination of what sprockets would be needed
speedmd
10 MW
I also need to grind off the pulley. I have a decent lathe so I pulled my motor apart thinking I could find a suitable way to chuck up the rotor. After looking at it a bit I decided the risk of damage from chucking it without a custom soft jaw nest was not worth it. Waiting on back ordered battery to do that part. At least for now.
Got the eccentric jack shaft bearing cups done. Has roughly 14 mm of adjustment. Working on a drive hub for the 72T sprocket next and will post photos when done.
This #25 chain is very tiny. Hope it holds up well.
Got the eccentric jack shaft bearing cups done. Has roughly 14 mm of adjustment. Working on a drive hub for the 72T sprocket next and will post photos when done.
This #25 chain is very tiny. Hope it holds up well.
Denisesewa
100 W
There is a source ( cant remember where at the moment) for Diamond brand #25 chain which is what I'll go with if replacement is needed, so far I see no sign of this cheap stuff failing thoughspeedmd said:
speedmd
10 MW
Great! I got a life time supply then.
It is nice and compact. Lots of engagement.
flyinmonkie
10 kW
I run #25 on my bike's primary reduction. It is a 1200w cyclone motor, but I run it to the back wheel instead of the chainrings on the final output. Anyway, I have nearly 1500ks on the #25 chain and I am now needing to replace it. I know recumpence uses the heavy duty #25 chain for his RC drives. It is pretty strong stuff.
Clay
Clay
justlooking
1 kW
McMaster.com lists the tensile strength of #25 chain as around 1000 lb
heathyoung
100 kW
Try the pitbike suppliers - there is 25 and 25H chain - the 25H is the heavy duty version, I think it has thicker sideplates and resists twisting better.
