RC downhill bike design -

[Miles]

Hal,

If you swap the motor drive chain to #219 (7.8mm pitch), you can up the ratio on that stage to 5.5:1

16t to 80t for the belt stage gives 5:1

27.5:1 in total

That's an increase on the present ratio and also solves the small pulley problem...

For 110 rpm crank speed the motor would spin at 3000 rpm. That ups the voltage to about 25 V.

 

[HAL9000v2.0]

Thanx Miles, you lead me to a goal... Whit this one I am quite satisfied...triple reduction and a hub gears. With 20/60 pulleys and 11/28 sprocket I get 1:23 at the end so it goes easily over 30!!! I used rest of the hxt shaft like idle shavt for second reduction and first reduction is idiling around pedal axis but inside bearing that holds all together.
Sorry to all, I am not quite eloquent in English so it is hard to explain all, look at the pictures then ask if something is not clear..

Dual hub gears is overkill now...So it will go...

 

[recumpence]

Looks beautiful!

A couple things;

#1 You have your pics showing XL pitch belt. Do not run that pitch. You have to run 5mm HTD or GT2 in 15mm wide to achieve the power you want.

#2 I would stay away from cheap motors for such a fantastic project. Not that you need a Plettenberg Terminator. But, a higher quality motor would be good. You could even go with a smaller Plettenberg motor in the 3kw range. Heck, even David's 40 series is good for 3kw burst or 2kw sustained and is far better quality than the HXT. That motor is $195.

I just hate to see such a beautiful design restricted to a cheapo motor.

Matt

 

[HAL9000v2.0]

thanks Matt,

1. Once again, this is a sketch and I make it form "stock" parts in 15 minute just to check if it is doable. This is AT5 Europe standard pulley (or international?) I will use HTD5/20 because this is easiest to find.
2. I bought this motor on first look, just found it, see the numbers and click "Buy". Actualy it will be better to have shorter motor with same diameter but this one has lov kV (130) . I have Plettenberg predator 36 but it was toooo expensive and I sold it shortly after buying.
Now when I have hxt I will rewind it and put new bearings and it will be ok. Don't know about this "David's" motor. Where can I find it?

 

[Miles]

Hal,

You can get one of these in 10turns (130 kv):
http://www.astroflight.com/index.php?main_page=product_info&cPath=9&products_id=122
http://www.astroflight.com/pdfs/3210.pdf

That HXT has budget stator material, so even with better copper fill it will never be that great.

If you want a cheapie to rewind, this would be better: http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=7870&Product_Name=TGY_AerodriveXp_SK_Series_63-74_170Kv_/_3250W You'll probably have to re-fix the magnets though..

Better to start with a Scorpion kit...

This was David's 40 series motor that Matt was referring to: http://www.rcgroups.com/forums/showthread.php?t=952325&pp=20

 

[HAL9000v2.0]

This one is not outrunner?

 

[Miles]

The Astro-Flight 3210 is an inrunner.

As your airflow will be minimal, I thought an inrunner would be better - especially with additional heat-sink.

 

[HAL9000v2.0]

By analyzing gear ratios with two identical hub gear (3speed) systems I noticed that there is always big ratio redundancy so best solution is one hub and 2 sprockets .

 

[Miles]

That seems like the way to go.... On my eMoulton I chose the sprocket sizes to fill in evenly between the hub gear ratios.

 

[Miles]

2 pairs of sprockets with a very wide ratio difference so that you double the range of the 3 speed? Each sprocket pair with its own chain - dual dog-clutch to engage one or the other?

 

[HAL9000v2.0]

If I make a dual it is not a problem to make a triple then I'll make 3 speeds 1:6 1:3 and 1:1. I am trying to avoid that it is doable but to much time. If I put two sprockets, one must be at least complete-ratio-of-a-hub bigger then other. This can be done only with clutch. Last night I have a dream about 2 speed retro-direct system with some kind of crank axle in pedals that changes direction of pedaling. It was not so clear. Like two retro direct systems one with big ratio difference as master drive and one on pedals but reverse with only a tooth difference.

 

[Miles]

Clutch is only slightly easier with 2 speeds than 3, I agree. I like the idea of 6 evenly spaced gears with 2 sprockets and 3 speed hub, though....

I'll have to give your dual retro-direct some thought... Could be quite lossy.....

There are quite a few 2 speed crank drives coming on stream. Maybe adapt one of those?

 

[HAL9000v2.0]

Look what I found
http://www.mbaction.com/ME2/dirmod.asp?sid=&nm=&type=news&mod=News&mid=9A02E3B96F2A415ABC72CB5F516B4C10&tier=3&nid=0E0745C6A30C4BEF940905670D9D4B01

 

[Miles]

Yes, looks good. There's the SRAM, the Nicolai/Bionicon and another one related to Schlumpf. Not cheap, though..... The Nicolai/Bionicon will be a while but the SRAM is available now.

 

[HAL9000v2.0]

Any link for SRAM?

 

[Miles]

http://magicmechanics.com/home.php?lang=en warning terrible website ........all the marketing hype never reached you ..........

 

[Miles]

http://www.schlumpf.ch/antriebe_engl.htm

 

[Miles]

Did you see this? http://iris.lib.neu.edu/getblob?blobid=1098686411726934 (posted by Boostjuice in the Resources thread).

 

[HAL9000v2.0]

That is amazing...Look at picture 9.. Phaser..that is what I have in mind...

 

[Miles]

I didn't doubt that your system could be made to work. I think so many close ratios would be a nuisance with power-assist, though...

 

[HAL9000v2.0]

Yeah, I like better the idea with 2 or three wide speeds since the motor itself can cover 1000 rpm area with similar efficiency.

 

[HAL9000v2.0]

I found this guys website. It is the same idea but his gear shifting plate movement is a little bit complicated to make but I like it.
http://www.nosmokemtb.it/UK_phaser.html
Thanks again for this finding, Miles

 

[Miles]

I vote for 2 sprocket/chain pairs and back-to-back dog-clutch between them (no need for separate registration).

 

[Miles]

Thanks again for this finding, Miles

Thank Boostjuice for posting it in the Resources thread :wink:

 

[HAL9000v2.0]

That is the main problem to this forum, I miss most of the good threads, while reading b.......