mud's RC motor reduction unit/MTB bike build

[mud2005]

I think they may have been comparing the two alloys at different tempers in your quote?

right again Miles, the 6063 is T53

Why not use square tubing instead of solid for the shaft? Probably cheaper, defintely lighter and more than strong enough, especially since it will be bolted or welded to the angle. If you are lucky the corners might be rounded enough to fit into the angle without grinding.

The square tubing I can find has up to 1/4" wall thickness and I want it to be a bit thicker.

I will most likely use a smaller piece for the shaft maybe something like this:
That will be cheaper and lighter and plenty strong.

Why not use belts for 8150's and smaller? I think the sprockets and pulleys are pretty much interchangeable.

Haven't decided yet I may go with belt drive, I was just looking at SDP and they have up to 72T 5mm HTD pulleys, but the bore is 3/8"
If I did that I would have to use 3/8" shaft or bore it to 1/2" ,hmmm more decisions

 

[dontsendbubbamail]

Haven't decided yet I may go with belt drive, I was just looking at SDP and they have up to 72T 5mm HTD pulleys, but the bore is 3/8"
If I did that I would have to use 3/8" shaft or bore it to 1/2" ,hmmm more decisions

I think that most folks are using the GT2 5mm pulleys with the 15mm belts. The 72T GT2 pulley has a 1/2" bore.

Bubba

 

[mud2005]

very cool, thanks Bubba

 

[mud2005]

time for another redesign

I got on the mill today and realised how big a PITA it was going to be to make this with a 4" x 4" piece of angle. so I sat down with my motor and some pieces of aluminium and came up with another simple design

The reason I like this one so far is it will be easy to cover the pulleys and possibly the motor too.

Thud was right,

I will design & redesign & tweek & re-tweek untill I have gone full circle & arive at the original design. :lol:
It is an easy trap to fall into,

I've lost count a long time ago how many times I've redesigned this, good thing it's fun to do

I also need to buy some aluminium pulleys to replace the plastic ones I have.

Anyone know where I can get a 15T 3/8" bore GT2 5mm pitch pulley?

The smallest I found on SDP in that bore was 24T. If there isn't one available I'm going to get the 15T 1/4" bore and enlarge it to 3/8", but that doesn't leave enough thickness in the hub for the set screws so I was going to put the set screws through the pulley like pictured here

does that make sense or is there a better way?

 

[Thud]

MUD,

I bored my 15t pully & the grub screws they provided were still fully enclosed in(what was left of) the hub. I also modified the large pulley (removed the hub to reduce width) just as you drew with no problem. I don't think you will have any problem getting them to do exactly what you want.
I will add that you need to get a 50% wrap on the 15t pully.

My current set up is fixed distance between centers(based on sdi's calculator) & I can jump the belt under max acceleration loads. I blame motor shaft flex. My 200lbs driven by a 8mm shaft is abuse. plain & simple.
keep designing, it is fun.

opps, your going 3/8"astro so it looks like if you want a hub. The 18t with the .68"hub is as low as you go.

 

[lawsonuw]

Another option is to use the 15T pulley and bore it out to 3/8. Next turn the OD of the hub down to 1/2 inch and slit the hub so a clamp collar can be used to hold everything together. Sdp-Si calls this arrangement a clamp hub. It's a very sturdy arrangement, and as long as you're not slipping it, this arrangement won't loosening over time.

Lawson

 

[mud2005]

thanks thud and lawsonuw, the hub clamp idea is an interesting one. I was thinking it could even be strengthed by drilling a hole in the shaft and putting a pin in that would go in the slit to prevent any slipping. The pin would be short enough so the clamp would still fit around the hub.

 

[mud2005]

some progress, made a new unit with 1/2" shaft getting some aluminium GT2 timing pulleys in the mail this week
The aluminium pieces are kinda weird sizes because I had them already cut from a previous project.
View attachment 1

 

[mwkeefer]

Thud,

Looking sweet! Can't wait to see the final product, still have a unit for me right?

-Mike

 

[mud2005]

Thud,

Looking sweet! Can't wait to see the final product, still have a unit for me right?

-Mike

think you posted in the wrong topic, I'm mud not thud

 

[mwkeefer]

Mud,

Sorry brother... long weekend, still that looks great... and thanks for reminding me to hound thud for my new thud transmission!!!

[feeling really stupid, busy over here... trying to link a pair of controllers and packing home office to be moved to new office location (as I prep the floor plans for the new office).]

-Mike

 

[Thud]

Mud,
still designing I see.
Have you thought about mounting senario's?
I can't seem to settle on any mounting position. The granny rack is simple & there are lots of bolt on's that would do it.
I used the seat post on my last build with good results, but wildly variable per bike.
On my future builds I will Proboably be extending the chain stay/rear triangle for mounting power units.
But unless there is a "frame specific" mount designed I think it will be on the end users to figure out a mounting senario.
looking good Mud.

mwkeefer: This is a prime example of why men shouldn't "multi task"

 

[johnrobholmes]

Looks nice and stout! With minimal fancy parts too, so surely it is pretty low cost.

 

[dequinox]

Hey Mud,

It looks excellent! Can't wait to check it out for real, so yeah we should meet up in Feb. when you have it together!

-D

 

[mud2005]

thanks guys,

Have you thought about mounting senario's?

probably too much I have an aluminium rack I built from 1/4" thick angle that might work, it sure feels strong enough. I also have the Bianchi single speed and the Haro bmx you see in the background.
I change my mind about which bike I want to electrify constantly
The Bianchi single speed takes the least amount of effort to pedal around, so it seems like it would make the most efficient e-bike, but the Gary Fisher is more of a beater and I don't mind clamping stuff to the frame and possibly scratching it.
The Haro is just plain fun to ride and I got a long ass seatpost so I can sit and pedal.
Decisions

Looks nice and stout! With minimal fancy parts too, so surely it is pretty low cost.

yeah didn't cost much to make, but took a long time. I'm going to make the next version just as strong, but easier to build.

It looks excellent! Can't wait to check it out for real, so yeah we should meet up in Feb. when you have it together!

for sure, I'll pm you when it's finished and we can race down the bike path

 

[dontsendbubbamail]

I have an aluminium rack I built from 1/4" thick angle that might work, it sure feels strong enough.

Personal experience says you need another brace from the front to the dropout.

Bubba

 

[mud2005]

how'd that happen Bubba? did your rack break or did the braze-on on the frame snap?

 

[dontsendbubbamail]

how'd that happen Bubba? did your rack break or did the braze-on on the frame snap?

The basic problem was that the front attachment mount was not strong enough. Pictures and description are over on this thread. Your design has the same type of failure mode that my rack had. The front of the rack can pivot into the wheel.

I also don't think that the standard 5 mm mounting points on the dropouts and seat stays are strong enough to handle the power. My solution was to create a bracket with more attachments points to bike and used a 3/8" bolt to attach the rack.

Bubba

 

[mud2005]

thanks Bubba, I had my doubts about the strength of the 5mm braze-ons also. I will beef up my rack for sure now before I mount anything on it. Wouldn't want to crack any ribs or my head for that matter.

 

[AussieJester]

Nice work there Mud...i would suggest some lightening holes though
other than that very nice simple setup well done

KiM

 

[mud2005]

Nice work there Mud...i would suggest some lightening holes though

thanks AJ, it is quite heavy. I bet I could drill out a bunch of weight. the aluminium is listed as 1.323 lbs/ft and I used 19.5 in. so I got 2.15 lbs. of aluminium there plus the weight of the shaft, bearings, and screws.
I could definitely lose some of that weight adding some holes in the aluminium and if I wanted to get extreme maybe even find a hollow shaft? maybe some ceramic bearings? are those lighter?
just throwing out ideas, I'm not sure if hollow shafts are even available and would probably be a bad idea since I need to add flat spots for pulleys. and ceramic bearings probably wouldn't be much lighter, but way more expensive.
anyway, lightening holes are a good idea, I'll add some soon

 

[kevo]

Mud,
Reading w/ great interest on your reduction unit build. Any updates greatly appreciated, great progress to date!

 

[mwkeefer]

Mud,

Barring my mistake the other day (overworked) I do like your design, simple and to the point.

I'm wondering if a standardized Kick Stand Mount could be figured for the recution unit, all my bikes (even my folders) seem to have a rather hefty chunk of mount down there... I know not all bikes have it but... well, nothing ever fits 100% of the time.

Do your rides have the kick stand mount plate? Will the reduction unit as it's sized now fit within the confines (I can't tell from the pics)?

No matter where u mount it, it's a great job just for the effort alone (assuming it works)!

-Mike

 

[mud2005]

Reading w/ great interest on your reduction unit build. Any updates greatly appreciated, great progress to date!

Progress was delayed for a while as I was lucky enough to get a web development project that actually pays I just finished the project a few days ago so development on the bike can resume.
I have everything I need to put a bike together except the time to do it. :|

Do your rides have the kick stand mount plate? Will the reduction unit as it's sized now fit within the confines (I can't tell from the pics)?

no, unless I extend the dropouts and move the rear wheel back I can't fit the unit there on any of the bikes I currently own.
I will most likely go with a custom rear rack motor mount similar to what Bubba did on his build.

Now that March is nearly here I can't wait to get this thing runnin. Its been too long having a pile of ebike parts lying around and no ebike. I'm going to start working on this thing even if I have to quit sleeping to do it

 

[dequinox]

Hey mud you ever gonna get this thing runnin?

Can't wait to see it put together. What tools do you have at your disposal, by the way? I was curious if you have having stuff machined outside your home or if you are building it all in your garage or what...