Mongoose DX project

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oofnik   100 W

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Re: Mongoose DX project

Post by oofnik » Mar 05 2009 3:22am

So, I'm long overdue for an update.
I went to visit Matt (recumpence) last week to check out his workshop. He put together one of his drives for me with all the parts. :)

But I'm now faced with a few more obstacles. I need to now mount the drive to my frame, probably using the clamp mounts very similar to the ones that Miles drew up in Alibre.

My next obstacle is clearance for my rear sprocket. My motor constant is 215 Kv (experimentally verified), rear wheel is 26" dia., and my battery voltage is ~40v. Matt's drive is 5:1. The smallest freewheel that will fit Matt's drive without modifying the freewheel adapter is a standard ISO thread 16 tooth. Doing the calculations to figure out what size driven sprocket I need to achieve a reasonable top speed comes out to about 56 teeth.

Correct me if I'm wrong, but I believe that the diameter of a 56T sprocket at 1/2" pitch can be calculated by multiplying the number of teeth by the pitch to get the circumference (28") and dividing by pi. So that would be about 8.9". That's pretty big. A lot bigger than disc brakes.

Well, to check if that sprocket would clear my chain stays, I cut out a cardboard circle about 9" dia. and stuck it where the sprocket would go.
IMG_4451_640.JPG
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No good. It's hard to see from the picture, but it definitely does not clear.

So now I have a few options:
1) Use a smaller sprocket
2) Sell the bike and buy a new one with wider chain stays
3) Use one of those motorized bike kit sprockets

Option one sucks because that means I'll have significantly less acceleration, a stupidly high top speed, and the motor will probably burn up. Option two sucks because it's just kind of a hassle. I don't have any particular emotional attachment to this bike but if I can avoid selling it second-hand for peanuts and shelling out even more cash for a decent replacement, I'd rather. Option three, then, seems to be the best bet.
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Those sprockets mount to the spokes with a set of fiber washers on either side of the spokes holding it in place. This is how most of the cheap 2-stroke engine kits drive the rear wheel. The advantage is that this would allow me enough clearance to fit the large sprocket as it's a lot closer to the spokes, thus further from the chain stays. The disadvantage, though, is how difficult they are to install and center properly. I also don't like the idea of squishing the spokes like that. But a lot of people use these kits and seem to have no problem.

What do you guys think I should do?

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Miles   100 GW

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Re: Mongoose DX project

Post by Miles » Mar 05 2009 5:08am


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Miles   100 GW

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Re: Mongoose DX project

Post by Miles » Mar 05 2009 7:49am

This was the one I was looking for:
http://motorbicycling.com/f3/top-hat-sp ... -2131.html

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Re: Mongoose DX project

Post by TylerDurden » Mar 05 2009 9:51am

I invited Andy (KingsSales) to check out this forum back in December, so he knows what we're up to... He's still pinging his myspace page, so you might see what he has in stock.

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http://profile.myspace.com/index.cfm?fuseaction=user.viewprofile&friendid=53429708
Have a Nice Day,

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Re: Mongoose DX project

Post by sockman » Mar 05 2009 10:20am

oofnik,

i'll be doing something very similar to your...same reduction, same wheel size, same rear sprocket diameter...

instead of mounting the sprocket to the spoke, i'm trying to make a adaptor to mount it on the inner side of the disk brake...now i have clearance issue with the brake caliper tot...(even with using the top hat adaptor it will not clear my deore caliper)

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Re: Mongoose DX project

Post by oofnik » Mar 05 2009 3:27pm

Miles,
Thanks for posting those links. I'm familiar with Andy's sprockets and I have seen that top hat adapter. I may go that route if I can find out if it will clear. If I went that route, however, I would be spending about $50 extra and I still wouldn't know if it would clear. I've e-mailed him and am waiting to hear back.

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recumpence   100 GW

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Re: Mongoose DX project

Post by recumpence » Mar 05 2009 6:41pm

Oof,

How goes it? Have you figured out the mounting yet?

I will be at teh shop almost the entire day tomorrow working on the beast!

Matt
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oofnik   100 W

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Re: Mongoose DX project

Post by oofnik » Mar 05 2009 8:13pm

Sockman,
Have you considered ditching the rear brake for V-brakes? A great majority of your stopping power comes from your front brake anyway. I find it fairly easy to lock up the rear wheel on my bike at any speed with my rear V-brakes - any more stopping power would be useless.

Matt - still no luck. I also just found out that those motorized bike kits use #415 chain which is 5/8" pitch, so that sprocket I posted a pic of won't work either.

Andy's sprocket with a top hat adapter may fit but that will cost me close to $100. And emphasis on may.

I'm currently looking at a 56T chain ring with a 130mm 5-hole mount. If I get that I will have a few mounting options. One will be to make a fiber washer spoke mount similar to the motorized bike sprocket mount. Two, I could make an adapter instead to go from the 130mm 5-hole pattern to the ISO 6-hole disc brake pattern, angling it inward to clear the frame (pretty serious machining required to make a part like that). Two would require me to lace up my rear wheel with the new disc brake hub, machine a custom part, and cost me a lot of money (probably more than Andy's top hat adapter).
I don't really know what to do. :(

Keep me posted on the clamp mount production. My school's bureaucracy and restrictions are extremely frustrating and I don't think I will be able to make them myself.

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Re: Mongoose DX project

Post by sockman » Mar 05 2009 9:16pm

oofnik,

its one of my options to remove the rear disc...unfortunately that would mean a new frame and wheel building for me...(my current frame only come with disc)...will measure the clearance again one i get my parts in....

i'll try to post some pic of wat i'm trying to do...hope we could come out with a simple solution since we share a common problem..

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Re: Mongoose DX project

Post by sockman » Mar 06 2009 10:26pm

Image

this is my adaptor for the left sprocket (pre machine)
need to machine it down (for weight) and check for clearance
planning to do 2 or 3 pc sandwich with the smaller pic to fit the "grooves" and bolt to the disc brake...

my original plan was to use a strida type belt drive...but couldnt find a cheap source for the pulley...

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Re: Mongoose DX project

Post by oofnik » Mar 07 2009 4:58pm

Here is my version of the "top hat adapter".
sprocketmount.png
sprocketmount.png (43.15 KiB) Viewed 2708 times
I spend a little time in Inventor drawing this up. It's intended to mount a 130mm chainring to a IS 6-bolt brake disc hub with a 12mm offset.
Now I just need to find someone who can make it...

Hey Matt! Is it doable?

Also, I was looking up the dimensions for the I.S. 6-bolt pattern. I could not find a single specification anywhere on the internet, so I pulled out my compass and calipers. I assumed it was metric. Does anyone have the exact numbers for the bolt spacing and such from the specification?

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recumpence   100 GW

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Re: Mongoose DX project

Post by recumpence » Mar 07 2009 5:22pm

I just made two of those (very similar to them) for my project bike, one for the front freewheel crankset and one for the rear dual sprocket setup.

Each one took me nearly 3 hours to make, though, because of their size versus the tiny machines I have. Yours is thicker, so would take alot longer to make on my machines.

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Miles   100 GW

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Re: Mongoose DX project

Post by Miles » Mar 07 2009 5:22pm

oofnik wrote: Also, I was looking up the dimensions for the I.S. 6-bolt pattern. I could not find a single specification anywhere on the internet, so I pulled out my compass and calipers. I assumed it was metric. Does anyone have the exact numbers for the bolt spacing and such from the specification?
There's nothing on the ISO site - I guess it's just an informal standard...

6 bolt 44mm BCD is all I've managed to find out.

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Miles   100 GW

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Re: Mongoose DX project

Post by Miles » Mar 07 2009 6:45pm

I think I would do it in 2 or 3 pieces.

Or even something like this?:
Attachments
Disc brake adapter.jpg
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Re: Mongoose DX project

Post by sockman » Mar 08 2009 12:32am

thats wat i'm trying to do...

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MitchJi   1 GW

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Re: Mongoose DX project

Post by MitchJi » Mar 08 2009 2:37am

Hi,
oofnik wrote: Matt's drive is 5:1. The smallest freewheel that will fit Matt's drive without modifying the freewheel adapter is a standard ISO thread 16 tooth. Doing the calculations to figure out what size driven sprocket I need to achieve a reasonable top speed comes out to about 56 teeth.

So now I have a few options:
1) Use a smaller sprocket
2) Sell the bike and buy a new one with wider chain stays
3) Use one of those motorized bike kit sprockets

What do you guys think I should do?
I think D came up with the most elegant solution. FW inside the large pulley and use either #219 (.306" pitch) or #25 (.25" pitch). (D used #219_. For 16t/56t you would have diameters of:
#219 .306 pitch = 5.45"
#25 .25 pitch = 4.45"

Off course you could use smaller drive sprockets and reduce the size even further (D used 11t).

Matt said (I don't know if there is enough interest to make it worth his while or not but it wouldn't hurt to mention it):
http://endless-sphere.com/forums/viewto ... 40#p136773
The one issue with the FW mounted inside the pulley is that when pedaling, the jackshaft will be spinning. That gives increased drag versus just spinning a freewheel.

If there is enough interest in a FW pulley, I can have Dave manufacture a number of them to fit a less expensive 16 tooth freewheel, rather than the expensive 22 tooth ENO. However, most people have not asked about it. I do have one other person who is interested. But, that is the only other one.
The shaft drag doesn't seem like a big deal (to me) and he could use one of the sick bike FW's (with the flange):
White Eno ($65):
Image
$20 (dicta?):
Image
Best Wishes!

Mitch


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Re: Mongoose DX project

Post by oofnik » Mar 08 2009 4:48am

Hi MitchJi, thank you for the suggestions! You've brought up some very good ideas.
I did some googling and found a plethora of sources for #25 chain pinions and sprockets. I'm kind of worried about #25 not being strong enough, but I've never used it - can anybody confirm whether this should be a concern?

Machining a freewheel down to mount to the inside of the synchro belt wheel seems like a doable option indeed. I found a 14 tooth #25 pinion on electricscooterparts.com with a 1/2" bore and two 90 deg. set screws that would go right on Matt's gearbox shaft.

It's all coming down to cost for me. I would hate to spend all the effort fitting a custom machined freewheel only to have it fail down the road. Not to mention the price on the work. And I'd still have to mount a #25 sprocket to my rear wheel some how. On the other hand, a top hat adapter and sprocket from Andy will run me $100.
I'll sleep on it and see what I think in the morning. :?

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Miles   100 GW

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Re: Mongoose DX project

Post by Miles » Mar 08 2009 5:21am

# 25 chain is probably strong enough if you get the HD version - the problem will be that it stretches so rapidly....

I think I would go with #219 chain and Extron composite sprockets, as I suggested for Deecanio's build.

The ENO freewheel won't fail in that situation - the torque through it will be reduced in proportion to the final reduction ratio......

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MitchJi   1 GW

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Re: Mongoose DX project

Post by MitchJi » Mar 08 2009 2:17pm

Hi Miles,
Miles wrote:# 25 chain is probably strong enough if you get the HD version - the problem will be that it stretches so rapidly....

I think I would go with #219 chain and Extron composite sprockets, as I suggested for Deecanio's build.
Isn't Matt using #25 for his second stage and if so is stretching a problem?

The smallest Extron I could find is 72t. I think that pushes the size back to just over 7" diameter.

Would the Ramsey silent chain in 1/4" or 3/16" pitch be good choices? If the width isn't too much for a strong enough chain and if sprockets are available in the correct sizes it seems like it might work well.
Best Wishes!

Mitch


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oofnik   100 W

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Re: Mongoose DX project

Post by oofnik » Mar 08 2009 3:58pm

Yeah, I checked his blog and he does use #25 for the second stage. I don't know how it's holding up; I know he hasn't ridden much over the winter.

Anyway I did some thinking. Here are the two options I'm considering now.
1) Get a freewheel machined in to the pulley, use a #25 15 tooth sprocket / roller clutch assembly on the output of the jackshaft, mount a 54T #25 sprocket to my rear wheel. This would require probably $50-60 in parts and more in machining work. Advantage: silent freewheeling.

2) Get Andy's top hat adapter and 56T sprocket, a standard 16 tooth BMX freewheel and use .5" pitch bicycle chain. This would require about $120 in parts and no machining work. Advantage: cheaper (maybe), freewheel easily interchangeable.

I think option two looks better at the moment. Hmm.

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recumpence   100 GW

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Re: Mongoose DX project

Post by recumpence » Mar 08 2009 5:22pm

I have 600 miles on my recumbent with #25 chain secondary drive. Yes, I have seem a small amount of stretch, but very small indeed. In fact, I do not have any adjustability in the idler for that chain, and it is fine. However, the motor rarely runs for long periods. I pedal alot. I would say that chain has about 150 miles on it. The motor runs at 8000 RPM with a 2 to one reduction to that chain. So, the chain primary sprocket runs about 4000 RPM.

I like that chain. They do stretch a bit more than other chains, but they are cheap and easy to replace.

Matt
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Re: Mongoose DX project

Post by MitchJi » Mar 09 2009 1:11pm

Hi,

If you are concerned about the strength of #25 if you can get the right sprocket sizes #219 will work well.
oofnik wrote:Yeah, I checked his blog and he does use #25 for the second stage. I don't know how it's holding up; I know he hasn't ridden much over the winter.

Anyway I did some thinking. Here are the two options I'm considering now.
1) Get a freewheel machined in to the pulley, use a #25 15 tooth sprocket / roller clutch assembly on the output of the jackshaft, mount a 54T #25 sprocket to my rear wheel. This would require probably $50-60 in parts and more in machining work. Advantage: silent freewheeling.
Why do you need a FW inside the pulley and a "roller clutch assembly on the output of the jackshaft"?
Best Wishes!

Mitch


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Re: Mongoose DX project

Post by liveforphysics » Mar 09 2009 1:31pm

#219 is great chain. They cell super low friction, super high strength versions of it for karts. Fantastic chain size.
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oofnik   100 W

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Re: Mongoose DX project

Post by oofnik » Mar 10 2009 2:36pm

MitchJi wrote:Hi,

If you are concerned about the strength of #25 if you can get the right sprocket sizes #219 will work well.
oofnik wrote:Yeah, I checked his blog and he does use #25 for the second stage. I don't know how it's holding up; I know he hasn't ridden much over the winter.

Anyway I did some thinking. Here are the two options I'm considering now.
1) Get a freewheel machined in to the pulley, use a #25 15 tooth sprocket / roller clutch assembly on the output of the jackshaft, mount a 54T #25 sprocket to my rear wheel. This would require probably $50-60 in parts and more in machining work. Advantage: silent freewheeling.
Why do you need a FW inside the pulley and a "roller clutch assembly on the output of the jackshaft"?
Obviously, when I said I did some thinking, I didn't do enough! :lol: Stupid me. Yeah, either a roller clutch or a machined freewheel would work. I guess I was thinking of the machining work required to mount the sprocket to my rear wheel, as I'm not aware of any available solution to do such a thing. Some sort of adapter would be required.
I don't know how much torque those freewheel clutches can handle, though. There are no specifications on that site. Anyone have more info?
rollerclutch.jpeg
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oofnik   100 W

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Re: Mongoose DX project

Post by oofnik » Mar 12 2009 1:14pm

oofnik wrote:I guess I was thinking of the machining work required to mount the sprocket to my rear wheel, as I'm not aware of any available solution to do such a thing. Some sort of adapter would be required.
Er, scratch that. I found a 54T sprocket ready to mount to a brake disc hub at 1/4" pitch. Awesome.

So, uh, nobody has any experience with those e-scooter freewheel thingies? :(

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