mud's RC motor reduction unit/MTB bike build

[mud2005]

I'm workin on it I swear I'm making slow but steady progress.
I made a bracket to mount my rear rack to the seatpost. It's a bit heavy but oh well it's strong
As far as tools I have a mini lathe and mini mill. I went to a few machine shops and at the ones I could afford I got sloppy work and the others would barely talk to me unless I had $$$ so I went the DIY route which is fun, but I'm learning so things take a bit longer.

 

[AussieJester]

Good effort with limited specilised tool Mud kudos to you
for having a go mate looking real good to Mud

KiM

 

[recumpence]

Mud,

You are going down the exact route I went down 7 years ago.

I bought an RC helicopter. As I was building it, I found a few things I didn't like. When I approached shops to make these parts for me, I got the cold shoulder. So, I went out and bought a couple mini-mills and a micro lathe. Then I had to teach myself how to use them. After that, I had to find material suppliers. At that point, I had to learn what cutters were best. It went on and on. However, at this point, it has all paid off. I can make nearly anything I want and I normally don't mess things up (normally). In fact, one [previously] HUGE multi million dollar shop that turned my small ($1,100) job away is now bankrupt. But, my little shop is still plugging along, and no, I am not working out of my home. I have been renting a shop for years. My business has survived while others have gone under. Ingenuity, my friend, ingenuity, that is what makes the works go around. :wink:

You are taking the correct path, my Son. Continue down this and you will achieve E-bike nirvana.

Matt

 

[dequinox]

I'm workin on it I swear I'm making slow but steady progress.
I made a bracket to mount my rear rack to the seatpost. It's a bit heavy but oh well it's strong
As far as tools I have a mini lathe and mini mill. I went to a few machine shops and at the ones I could afford I got sloppy work and the others would barely talk to me unless I had $$$ so I went the DIY route which is fun, but I'm learning so things take a bit longer.

Wow nice job on the seat post clamp, are you using the harbor freight mini machine stuff? Also I'm surprised you got the cold shoulder from people at the machine shops. Then again I got lucky and got my parts done at the first place I went to. Wasn't cheap but was fairly reasonable. 23rd & A Machine Shop in Springfield. He seems a bit sketchy at first, with his cluttery shop and old scrappy dog, but I think he's a really reasonable dude. He made three parts for me for about $130. They weren't exactly simple things either. A bearing block, a freewheel adapter for my jackshaft and a sprocket mount for the other side of the jackshaft.

 

[mud2005]

thanks KiM

You are taking the correct path, my Son. Continue down this and you will achieve E-bike nirvana.

thanks Matt, I'm pretty sure most people I know right now think I'm crazy spending my limited $ on my ebike obsession so it's good to have positive input.
If I'm anywhere near your skill level 7 years from now I will be thrilled your current trike build is too cool for words 8)

Wow nice job on the seat post clamp, are you using the harbor freight mini machine stuff?

pretty much, but I got the micro mark versions. It's made by Seig also, but with a couple changes such as using inches instead of metric.

$130 for 3 parts does sound reasonable good to hear there's someone around here that helps out with small projects.

 

[dequinox]

Oh and PS if you ever need any welding done let me know. I can't really do aluminum at home since I don't have the setup but for any steel thing you want built I'd be happy to donate a few welds for.

 

[mud2005]

Oh and PS if you ever need any welding done let me know.

sweeeet! I know a welder!

you're gonna be sorry when I show up at your door with a pile of tubes and a napkin sketch of the frame I need

just kidding, but thanks for the offer I am fascinated with welding and mostly would like some help buying an affordable welder and learning to use it. but first of course I have to put this ebike together and finish a few other projects I've been putting off.

edit: almost forgot, you can also let me know if you need any parts made on the lathe or mill. maybe we can trade welding for machining

 

[mud2005]

got the rack mounted. It's attached to the skewer for now, I will most likely change that in the future. I may make a bracket to attach it to the frame or I may mount the motor elsewhere, I'm not sure yet.

and I ground some flats on the reduction unit shaft
slow and steady progress

 

[mwkeefer]

Mud,

Now that I clearly see how your mounting the whole rack assembly, a small suggestion...

I would skip the seatpost clamp and simply go with a wishbone shaped piece which has 2 clamping points to the inner downtubes (below the seat post) which would have better rigidity and won't transmit vibrations into your rear end (yours not the bikes) - I just think that for the most stout mounting possible, it would be a better option...

If your looking for FAST removal and install then stick with the seat post, high power and more permanent... make a new brace bar for your rack = )_

Looking good!

-Mike

 

[mud2005]

thanks for the suggestion on the rack. I haven't had much time lately so I just wanted to get something together as quickly as possible.
I'm going to try out the rack as it is and then I'll probably take it all apart and rebuild it again.
First I wanted to make sure a rear rack is going to work at all. I'm a bit worried the torque of the motor will flex the rack and cause the chain to come off. I may have to make the whole thing alot stronger, but I won't know for sure until I try it.

 

[dontsendbubbamail]

thanks for the suggestion on the rack. I haven't had much time lately so I just wanted to get something together as quickly as possible.
I'm going to try out the rack as it is and then I'll probably take it all apart and rebuild it again.
First I wanted to make sure a rear rack is going to work at all. I'm a bit worried the torque of the motor will flex the rack and cause the chain to come off. I may have to make the whole thing alot stronger, but I won't know for sure until I try it.

My rack is 1/2" welded steel tubing. It flexes more then I ever thought it would. The only reason I noticed it was because I had the bike on a trainer while testing. Did you use larger bolts where the rack attaches to the drop outs?

Bubba

 

[Grinhill]

I'm going to have similar issues with my rack design.

A common way of increasing strength without going to much heavier struts is to use triangular shapes.

Only problem here is that this style rack is fairly tall and skinny - and tall skinny triangles aren't quite as strong as equilateral ones.

Sorry, not much help here, just thinking aloud...

 

[Thud]

For stiffness....you need to have "triangulation" on the supporting moments of the structure.
for a sugestion, I would look at tying together the upright members above above the wheel with a cross member (welded perfered) I know it makes it taller but the more angle you can get in the cross member the stiffer the assembly. look at it from all angles.

Mud-look at the aluminum-brazing options (alumiloy or whatever they market the stuff as)
http://durafix.com/
used properly it actually works very well.
some thing like this:

this is a built "box" structure that will stiffin the side to side wag in your set ups.

food for thought.

 

[amberwolf]

If you need a stiffer rack and can weld or braze up your own or add to an existing one that is already made of welded/brazed-together tubing, without pivot points at the dropout risers to the back of the rack, then you can weld/braze in a triangulation tube parallel to the seatstay from just above the dropout mounting point to just in front of the seatpost clamp.

If there are pivot points then it isn't going to help much because the pivots can move too much, usually. But if it is solidly constructed with tubing then it will help.

If the rack is tall enough above the wheel at the rear, you can also add a X crossbar across the dropout risers from side to side, which will stiffen it against sideways sway even more.

 

[mwkeefer]

Actually as I look even closer, I see a better option...

Make an inverted L bar with a clamping recess which affixes below the seat post to the seat down tube... run the length of the bar through the rear V (bracing it there too if possible) and finally up to your toung mount on the existing rack pan.

That will give you (with the upper arms braced too) the triangulation thud is referring to (which I couldn't think of last night).

I could draw a rough napkin up for you if I am still not conveying this correctly (take me less time to hand sketch than use CAD).

It is all the same very cool - excellent job so far!

-Mike

 

[mud2005]

Did you use larger bolts where the rack attaches to the drop outs?

no, I just drilled holes for the skewer and the braze ons. I had to use a longer skewer.

thanks for all the great suggestions on making the rack stronger. I noticed tonight that even if I tighten the clamp on the seatpost very tight I can still make it move side to side if I push on the back of the rack.

It's going to take some time to refine this design. I'm also considering using my bmx instead because the dropouts are huge and already have holes above where the axle goes which I can attach a rack to. plus with the 20" wheels the rack doesn't need to be as tall so it will be stronger.
The drawback of the bmx though is there's not much room in the triangle for Lifepo4 battery
I've also considered extending the dropouts back 3" and down 3" and using a 20" wheel on the MTB. problem with that is I then lose the brakes.
another idea is to make the rack much shorter and clamp it to the frame instead of the dropouts.
anyway I'm going to look into making a stronger rack with some triangular bracing for now and hope for the best

I could draw a rough napkin up for you if I am still not conveying this correctly

a sketch would help if you don't mind, its hard to picture otherwise.

and thanks to amberwolf and thud for taking to time to sketch up those ideas.

edit: the main reason I opted for a rear rack motor mount is that where I live it rains all winter and I wanted to keep the motor high and dry.

 

[dequinox]

Hi Mud,

I have added a few notes to your picture for what I think would be the easiest way to stiffen up your rack.

The red line indicates where most of your current flexing will occur. Double-red lines indicate more critical braces, with the short vertical ones being optional until you've tested it out more... Yellow spots are where I think you should add an angle-bracket around the corner to prevent bending-moment stress on the bolts. Since you only have four pins this will help keep the frame "square" as well. The green lines indicate the bracing that will be provided by the solid plate on your reduction unit.

Where that short vertical braces are I think you can easily tie into your brake cantilever mounts. I've seen others do this where they have a front rack with a longer bolt, and simply put a spacer between the bracket for the rack and the actual brake arm. A spacer of the right diameter will not affect the movement of the brakes. The yellow diagnonal brace would be extremely optional I think... you'd only need it if things really were flexing around.

Note that you're going to see left and right cavitation as well, some due to the motor and some due to the inertia of all that metal during turns. Amberwolf's cross brace isn't a bad idea...

 

[mwkeefer]

D,

While I like the suggestions... unless he is converting to Disc brake, I would avoid using those caliper bosses - normally they are weakly braised to the frame and in this case a rack failure could lead to a full rear brake failure (breaking off the bosses).

I will draft up somthing which should be safer and more rigid - one thing, Mud - what type of aluminum Lbar is that? and what are the thicknesses?

-Mike

 

[dequinox]

I intended for the brake boss braces to be a bit more optional than the rear long-brace and the corner braces. The rear braces should be enough I think. If the bosses are welded then he should be fine using them...as long as he uses higher grade screws in them. Say...grade 8 ought to do it. Mud you can pick those up at Eugene Fastener...they have all sorts of specialized stuff if you don't already know...

 

[mud2005]

Mud you can pick those up at Eugene Fastener...they have all sorts of specialized stuff if you don't already know...

I freakin love that place I go there all the time. They have so much more stuff than any of the hardware stores in town.

I'm looking into attaching the gearbox in a different way that will eliminate the need for the rack and will be much stronger.
I will post a sketch as soon as I have the time,

Again thanks for all the suggestions on making a stronger rack. I almost feel bad if I end up not using the rack now

I'm sure some are getting used to my constant changing design at this point though

 

[mwkeefer]

Mud's RC Motor Reduction Unit / MTB bike build / Transformer = )_

-Mike

 

[mud2005]

ok I lied, I did use the rack

made a simple change by moving the vertical braces to the back of the rack. seems pretty sturdy so I mounted the gearbox on the rack and I like the way it looks

I would have put the chain on, but I need to get a #25 chain breaker.
the weather is warming up and I need to get this thing on the road

 

[mwkeefer]

Looking good!

-Mike

 

[AussieJester]

Looking very good mud ...this is very much like what
Grinhil is attempting to do isn't it?

KiM

 

[mud2005]

thanks guys

this is very much like what
Grinhil is attempting to do isn't it?

I guess it is, I somehow missed that thread. now that I've seem it I really like the idea of mounting the motor under the rack for weather protection and putting the battery on top which is easier than putting it in the triangle. nice design grinhill

I will most likely put a plastic cover of some sort over the drive unit and mount the battery in the triangle. I would have put the battery on the rack, but I've tried putting 10lbs on a rear rack and didn't like the way the bike handled. hopefully the battery in the triangle will balance it out enough.