DH Comp Rotomax Mid drive

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Feist92   10 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Jul 13 2019 9:04pm

Ive made up a sprocket adapter and fitted it to the bike, I was in a bit of a rush so the machining is a bit rough in places but it turned out ok. Ive just mocked it up for now.
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Im starting to look into chucking the battery in a back pack as I cant fit it where I wanted to under the down tube. Im fairly sure the front wheel will hit it under full compression

I decided to take the shock off the frame so I could check the chain growth with my intended routing but ran into a significant problem. Almost every part of the suspension linkage has been munted by the guy I bought it off. Its been bodged together so I had no idea how bad it was till now. Safe to say its really killed my motivation
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DanGT86   10 kW

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Re: DH Comp Rotomax Mid drive

Post by DanGT86 » Jul 13 2019 9:53pm

Sorry to hear about the suspension. I'm always amazed they hold up as long as they do. Everything on bikes seems impossibly thin. Looks like you have the skills to repair or remake the suspension parts if you have to. You could probably bore and sleeve some of those parts and they'd be stronger than ever. It does suck having to go back and make stuff you thought was fine. Maybe take a break from it and go ride something else to get your motivation back.

The work looks awesome so far. Hurried rough machining looks cooler than smooth machining to most people anyway.

cheapcookie   100 W

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Re: DH Comp Rotomax Mid drive

Post by cheapcookie » Jul 14 2019 1:37am

Son of a gun! looks like a mean machine!

Is the motor output freewheeled ? or can take advantage of regen braking ?

xiteamxi   100 mW

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Re: DH Comp Rotomax Mid drive

Post by xiteamxi » Jul 14 2019 7:29pm

Old thread.. but looks like no freewheel so regen possible, would be nice to see if this project was ever finished some nice machine work going on there... with a good battery no doubt this thing would be an animal.

flat tire   1 MW

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Re: DH Comp Rotomax Mid drive

Post by flat tire » Jul 14 2019 7:43pm

Bike looks nice, battery backpacks suck hard and top tube battery mounts are an easy solution on any bike.

Feist92   10 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Jul 21 2019 7:15pm

Ive done what should be enough of a fix for the mean time, it might even be stronger than before but it is a bit ugly.
The shock should be ok for some testing but it really is a bit naff
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j bjork   1 kW

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Re: DH Comp Rotomax Mid drive

Post by j bjork » Jul 22 2019 6:25am

Nice build, keep it up :thumb:

Feist92   10 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Aug 17 2019 11:45pm

So I just broke some of the wires in the motor trying to add internal hall sensors.
I guess I'm rewinding the stupid thing

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neptronix   100 GW

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Re: DH Comp Rotomax Mid drive

Post by neptronix » Aug 17 2019 11:53pm

That sucks to hear :lowbatt:
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: 20" eZee on a Cannondale Semi Recumbent.
Whipper-snapper: ? on a lightweight BikeE Semi Recumbent

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DanGT86   10 kW

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Re: DH Comp Rotomax Mid drive

Post by DanGT86 » Aug 18 2019 1:18pm

That does suck but at least you'll know its done well. My 80100 outrunner had strands of wire that were loose and just hanging out if the bunch. Some were long enough to scrape on the magnets or get wedged in the air gap. Quality control isnt exactly what these motors are known for.

Feist92   10 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Oct 05 2019 9:21pm

Ive been a bit slack with this project recently but Ive got one phase wound on the motor. The cross sectional area is up by 15% and also an additional 2 turns so the copper fill should be a fair bit better than it was before
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SlowCo   100 kW

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Re: DH Comp Rotomax Mid drive

Post by SlowCo » Oct 06 2019 9:23am

Great work and nice build!

Feist92   10 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Oct 18 2019 11:43pm

Been a bit slack but I finally finished winding the motor. Its turned out quite well and passed a 500V insulation test without any issues
I ended up starting again from my last post and added some extra wire
It has 30% increase in cross sectional area and an extra turn to get the Kv down which results in 63% more copper
Glue is setting on the hall sensors as we speak so will wire them and a temperature sensor as soon as I work out which one to use.
Now I just need to find a suitable controller
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SlowCo   100 kW

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Re: DH Comp Rotomax Mid drive

Post by SlowCo » Oct 19 2019 4:10am

Great work!
What is the kV of the motor now?

Feist92   10 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Oct 25 2019 2:57am

SlowCo wrote:
Oct 19 2019 4:10am
Great work!
What is the kV of the motor now?
Thanks. Im not sure tbh I havnt put it together yet and dont have anything to measure it with. Ill probably wait till I glue in a temp sensor before putting the thing back together again

Feist92   10 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Jan 04 2020 3:27am

Sorry for the lack of updates.
In this period of radio silence Ive added hall sensors and a thermister to the motor, machined the parts for the chain tensioner and idlers and also the pulley for the motor shaft.
Ive decided to run the printed pulleys to confirm Ive got the ratios somewhat right before sinking heaps of time into machining the pulleys. That and Im curious to see how long they last if at all.
So short of machining up some bushes for the chain tensioners and a belt idler all I need to get this moving is a motor controller
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Hallgoodern   1 µW

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Re: DH Comp Rotomax Mid drive

Post by Hallgoodern » Jan 29 2020 5:53pm

Wicked engineering bud.
Can I ask what size drive chain you are using and where you got the sprockets from please?

Hallgoodern   1 µW

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Re: DH Comp Rotomax Mid drive

Post by Hallgoodern » Jan 30 2020 1:37am

Wicked eh bud,
What gauge drive chain are you using,?
Did you print the drive chain sprockets as well?

Zeurus   10 mW

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Re: DH Comp Rotomax Mid drive

Post by Zeurus » Feb 07 2020 2:15pm

really nice machining:) youre doing quite the same way as we did with our first conversion. love it XD

greetings from Austria:)
27.5''plus Hardtail :wink:
viewtopic.php?f=6&t=103637

26'' Fully with 6374 and VESC
viewtopic.php?f=6&t=99610

Feist92   10 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Feb 15 2020 3:03am

Hallgoodern wrote:
Jan 30 2020 1:37am
Wicked eh bud,
What gauge drive chain are you using,?
Did you print the drive chain sprockets as well?
Its just a 219 go kart chain. The drive chain sprocket is printed atm but thats just for a fit check/ curiosity, Ill machine a proper one after I prove it moves and the reduction is about right.
Zeurus wrote:
Feb 07 2020 2:15pm
really nice machining:) youre doing quite the same way as we did with our first conversion. love it XD

greetings from Austria:)


Oh wow your builds are very impressive, I wish Id seen those before starting mine. I have to concede that your machining is more impressive, that pulley with the fan blades machined into it is very cool!
Are you running VESC controllers? Im thinking I should bite the bullet and try one even if they dont have the output Im after

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DanGT86   10 kW

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Re: DH Comp Rotomax Mid drive

Post by DanGT86 » Feb 15 2020 12:06pm

Speaking of machining, how long have you been at it? Do you program setup and run parts for a living or just some of those tasks? I'm curious because I personally do all three at work. I even have a 5axis machine center to play with but I feel like everyone builds cooler stuff than me.

I am relatively new to the 5axis and CAM/CAD stuff and spent about 14 years making pretty simple parts on a conversational control. Its only been the last 3 years that I have had all the fancy tools at my disposal.

Personally the thing I struggle with is the initial design. Having the tools doesn't make me an engineer or industrial designer. I'm reminded of that every time I try to make something from scratch.

How about you Zeurus? Whats your CNC Machining experience?

Feist92   10 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Feb 15 2020 2:27pm

Out of high school I did a fitting and machining apprenticeship which was all manual machining. I had been dicking around with CAD a year or two before that but was self taught so was ok but never that good at it. As soon as my apprenticeship was over I got a job working with some incredibly talented design engineers so some of that has rubbed off, recently Ive picked up enough so that designing stuff is now a part of my job. On the CNC side I made friends with the CNC machinists at work and got one of them to run me through the basics of what buttons do what and how and when to do things then taught myself how to program parts and run the machine.
Design is a bit of a c#%t coz its too easy to try and perfect things before making them but if you do that you spend months designing stuff and never make anything. On the other side of that coin theres always better ways to do something, theres definitely a lot of thing Id change on this thing if I were to do it again but in saying that this was always going to be a proof of concept.

The only advice Ive got is that 3d printers are awesome. Its super helpful being able to design something, print it out, fit check it and even just hold it and see what looks right and where you can take unnecessary material away

Zeurus   10 mW

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Re: DH Comp Rotomax Mid drive

Post by Zeurus » Feb 16 2020 5:30pm

i would'nt go for the vesc, especially if you have got the battery in a backbak. my vesc burnt cause of voltage spices due to the long battery wires. for skateboards its good. try the nucular controller12f (or24f)... its worth it. driven now 1300km (mainly steep trails in the mountains) and works awesome.

DanGT: yeah im working with cnc-machines now for 10 years. but starting your own stuff is always a tough quest. producing small pneumatic valves and cylinders is not quite the same as a bike conv.

we did our first conversion. worked but there always things to improve. fail/learn/repeat^^
after our 2nd conversion we did a complete bike, cause on a normal bike youre always limited in the way of design...
Actually were building ourselfe a big Autoclave to build a strong carbon frame :) (our bike runs really good, but well theres always something to improve^^)
27.5''plus Hardtail :wink:
viewtopic.php?f=6&t=103637

26'' Fully with 6374 and VESC
viewtopic.php?f=6&t=99610

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sn0wchyld   1 MW

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Re: DH Comp Rotomax Mid drive

Post by sn0wchyld » Feb 16 2020 10:11pm

Feist92 wrote:
Feb 15 2020 2:27pm

Design is a bit of a c#%t coz its too easy to try and perfect things before making them but if you do that you spend months designing stuff and never make anything.

Dear god do I ever know that feeling.

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