bzhwindtalker
100 kW
Enuf CAD for today, I saturate 
LMX P2 : Freeride trials motorcycle frame development
- Thread starter bzhwindtalker
- Start date
r3volved
100 kW
I assume this will have pegs vs. peddles?
Curious...What's the reason for flipping the drive side to the left and brake side to the right? Is there an advantage?
Curious...What's the reason for flipping the drive side to the left and brake side to the right? Is there an advantage?
bzhwindtalker
100 kW
Yes the bike will use pegs, I found out footpegs allow me to ride way more aggressively vs pedals! plus adding a pedal drive line and a motor driveline ies added complexity for little advantage...
I have the drive line on the left because a friend makes very nice rear hubs made for left side drive on ICE bikes, but i'm not sure yet about that.
I have the drive line on the left because a friend makes very nice rear hubs made for left side drive on ICE bikes, but i'm not sure yet about that.
crossbreak
1 MW
the braces look good on your last pics. Guess you wont use pipes much thinner than 25mm, so it makes almost no difference if not every path of force is absolutely straight.
The only thing I would change: Weld a piece of flat iron to the lower rear corner of the frame and mount you swing arm on that. The way you mounted your swing arm pivot weakens the whole structure in that area IMO.
The only thing I would change: Weld a piece of flat iron to the lower rear corner of the frame and mount you swing arm on that. The way you mounted your swing arm pivot weakens the whole structure in that area IMO.
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simply awesome!
I'm after your opinion on the motor arrangement as my builds' looking fairly similar minus the home built frame. Do you think its wise to add an additional bearing on the far end of the motor shaft to brace against chain tension? (especially for you as bashing the swing arm/chain on rocks doing trials is inevitable.)
if these motors are built anything like the ones i have from mrtao i seriously doubt the durability of motor bearings alone.
all the best!
I'm after your opinion on the motor arrangement as my builds' looking fairly similar minus the home built frame. Do you think its wise to add an additional bearing on the far end of the motor shaft to brace against chain tension? (especially for you as bashing the swing arm/chain on rocks doing trials is inevitable.)
if these motors are built anything like the ones i have from mrtao i seriously doubt the durability of motor bearings alone.
all the best!
bzhwindtalker
100 kW
I hear you on the rear bracing, something I'll keep in mind! On the tubing I plan to use 20*1,5 25cd4s tubing. I found some rear swingarms in steel, so easy to modify as needed, with 395+-22 axle to axle size. 40€ from a shop 45minutes from Lyon.
litespeed
100 kW
Any of the suspension mounting points need to be double shear to make sure they last and no regrets. From what I can see it looks nice but only part of the picture shows up on my computer.
Tom
Tom
Joe T.
100 W
litespeed said:
I have the same problem. If you right click on the image and choose view image, it will show the whole picture
crossbreak
1 MW
litespeed said:
here are some examples. All of them are "double shear", but solved a bit different. The motorcycle for example has just a hollow bolt between the left and right pivot + a through-bolt that goes through the whole bearing assembly. The swing arm sits in between the frame tubing. All of the bicycles have welded structures that make the pivots double shear.
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crossbreak
1 MW
I just saw that on the last pic you can see a flat iron welded to the frame tubing as well, which takes the pivot. I wasn't aware of that when i shot the pic, sorry for bad qualy
bzhwindtalker
100 kW
crossbreak said:The 200mm wide swing arm would need a lot of spacers.. which does'nt make it any stiffer. I'd prefer a more narrow swing arm.
Additionally, it is only 400mm long. So a 24" wheel will not fit I guess. Have a look at this one:
http://cenkoo.de/shop/product_info.php?products_id=888
it's 450 mm long, has 295mmradial tyre clearance. It's made for 14"x3.0" moped tires just like the one you fount....It would still fit a 21" bycicle tire. A 24 x 2,35 (60-507) tire wouldn't..besides it would look funny since a 2.35" tire is quite narrow.
Which rear hub? 142x12mm shimano through axle hubs are not that expensive. They start at 40€.would need a custom swing arm.. maybe a Moped hub would be even cheaper, I guess they have 36 spockes as well.
I received the swingarm and you were rigth, it's not gona work!
Where do you find the shimano hubs? I may design a rear swingarm for 12mm*142 if the price is this low, but no reger or engine braking with the freewheel. do they exist with freewheel mount?
crossbreak
1 MW
this one: FH-M640 E-Thru
http://www.bike-discount.de/de/kauf...6-loch-87411?gclid=CMWd_56Nmr0CFQUIwwod2zYAPw
Freewheels are dead since decades in this price region. maybe surly makes something special
http://www.bike-discount.de/de/kauf...6-loch-87411?gclid=CMWd_56Nmr0CFQUIwwod2zYAPw
Freewheels are dead since decades in this price region. maybe surly makes something special
crossbreak
1 MW
for my fist tests i wanna use this one: http://endless-sphere.com/forums/viewtopic.php?f=28&t=56268#p837789
maybe i try something like this:
maybe i try something like this:
bzhwindtalker
100 kW
Thanks for the info!
I designed a custom swingarm to fit :
I designed a custom swingarm to fit :
Adam, do what ever you can to get the swing arm pivot as close as possible to the drive motor shaft and the swing arm pivot as high as possible within the chain run, even if the chain rides over the swingarm a little until the suspension is loaded with the riders weight.
They don't do it this way just for the grin!
http://p.vitalmx.com/photos/stories/2013/10/10/full_IMG_0888_971012.jpg?1381393194
Don't be tempted to put them all on the same centre line with the suspension unloaded, your tightest chain will be at full suspension extension with it getting progressively slacker as the suspension compresses! getting the swing arm pivot closer to the motor minimises the tension change and raising the pivot point will have the tightest spot part way through the suspension travel reducing the amount of slack at full compression. and also reducing the squatting effect of applied power.
They don't do it this way just for the grin!
http://p.vitalmx.com/photos/stories/2013/10/10/full_IMG_0888_971012.jpg?1381393194
Don't be tempted to put them all on the same centre line with the suspension unloaded, your tightest chain will be at full suspension extension with it getting progressively slacker as the suspension compresses! getting the swing arm pivot closer to the motor minimises the tension change and raising the pivot point will have the tightest spot part way through the suspension travel reducing the amount of slack at full compression. and also reducing the squatting effect of applied power.
crossbreak
1 MW
i agree.
What about mounting the motor on the swing arm directly. If it's custom made anyway I would prefer that, no more chain slack. No more jerks if load changes
What about mounting the motor on the swing arm directly. If it's custom made anyway I would prefer that, no more chain slack. No more jerks if load changes
bzhwindtalker
100 kW
Did some modifications going this way, but I don't want to push it too far with the issues I had mon my P1 frame where the chain would pull exactly on the pivot point. This caused unmanagable chain growgth. I did some tests on the current geomety and the chain lenght variation over travel is very small.
Next week I'm printing my scale 1:1 drawings and hopefully satrt the build soon after that. I still need to design a jig for the swingarm.
Next week I'm printing my scale 1:1 drawings and hopefully satrt the build soon after that. I still need to design a jig for the swingarm.
crossbreak
1 MW
ok.. why?
bzhwindtalker
100 kW
The gear ratio used involved a big front sprocket.
Looks like you had the opposite problem with the first frame, the idea is to get the 2 sprocket centres and the swingarm pivot in line with the riders weight on the suspension, this is where the chain will be the tightest, then you will have a little slack compressed and a little when extended. The amount of slack created is minimised by keeping the pivot close to the drive sprocket centre. Do this and you wont need a tensioner. On your old setup the swing arm pivot is way too high! they where never going to come into line, you would not have enough travel to get the swingarm up high enough, so your chain was tightening all the while as the suspension compressed, set too tight it would limit suspension travel, set the chain tension to allow all the travel and it would be too slack when the suspension extended.
crossbreak
1 MW
ah ok got it. Something in between looks like most enduros. Same with mine, i'll try to keep it as is.. As soon as I got laced my wheel i'll post a pic.
Was hard to make your LMX pivot double shear on both sides i guess. A lot of work.. but worth it IMO... why didn't you mount your motor on that swing arm already.. would have been the same work.. or do I miss something here?
Maybe cut those ends from thick sheets by laser, then you'll have to do only little by yourself (dremel a bit and weld it up) would save you from that hard work you had last time
Was hard to make your LMX pivot double shear on both sides i guess. A lot of work.. but worth it IMO... why didn't you mount your motor on that swing arm already.. would have been the same work.. or do I miss something here?
Maybe cut those ends from thick sheets by laser, then you'll have to do only little by yourself (dremel a bit and weld it up) would save you from that hard work you had last time
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- Feb 15, 2013
- Messages
- 1,903
mounting a large motor on the swingarm will increase unsprung weight..
& necessitate a longer swingarm thereby slowing down the bikes handling
trial bike/mtn bike/dirt bike, all have relatively short chainstay/swingarm for nimble handling..
chain slack under suspension movement should not be a major issue if the design is optimized to reduce/eliminate it..
& necessitate a longer swingarm thereby slowing down the bikes handling
trial bike/mtn bike/dirt bike, all have relatively short chainstay/swingarm for nimble handling..
chain slack under suspension movement should not be a major issue if the design is optimized to reduce/eliminate it..
crossbreak said:ah ok got it. Something in between looks like most enduros. Same with mine, i'll try to keep it as is.. As soon as I got laced my wheel i'll post a pic.
Was hard to make your LMX pivot double shear on both sides i guess. A lot of work.. but worth it IMO... why didn't you mount your motor on that swing arm already.. would have been the same work.. or do I miss something here?
Maybe cut those ends from thick sheets by laser, then you'll have to do only little by yourself (dremel a bit and weld it up) would save you from that hard work you had last time
crossbreak
1 MW
if the motor is close to the pivot, its influence is negligible. the wheelbase does not have to be longer either, thats just a design question.
