Hi Max,
I'd say "put a serious compression load on that thing and it's gonna buckle" because I just feels it in me water.
2Many's technical explanation tells it a lot better.
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Sproket alignment, Frame problem?
- Thread starter Gmorrone1214
- Start date
Hi Max,
I'd say "put a serious compression load on that thing and it's gonna buckle" because I just feels it in me water.
2Many's technical explanation tells it a lot better.
Max Midnight
XS650 Addict
What I like about forums such as this is that it raises questions that prick my curiosity, such as 'how much force goes through a brake torque arm?'
So, if my internet searches have given me good info. and I have made the correct calculations these are my conclusions:
Force = Mass x Acceleration
An XS650 weighs around 195kg + rider of (say) 100Kg
Maximum deceleration from the rear brake = 0.4g (source here, bike was a 1994 BMW - not an XS but all I could find)
Deceleration force would be 1158N or 26lbs
Using this spreadsheet here and using a 0.5" tube of 0.035" tube thickness and 12" long gives a margin of safety of 830% for steel and 279% for aluminium.
However, no-one in their right mind (IMHO) would brake only using the rear so the force would reduce as more front brake is applied.
I therefore draw two conclusions from the above:
1. There is more than enough strength in a steel torque arm to withstand the compressive loads.
2. I should get a life, try to get out more and re-join the human race.
Of course there is the probability that the above is completely wrong so will happily bow at the feet of those with greater knowledge than I.
So, if my internet searches have given me good info. and I have made the correct calculations these are my conclusions:
Force = Mass x Acceleration
An XS650 weighs around 195kg + rider of (say) 100Kg
Maximum deceleration from the rear brake = 0.4g (source here, bike was a 1994 BMW - not an XS but all I could find)
Deceleration force would be 1158N or 26lbs
Using this spreadsheet here and using a 0.5" tube of 0.035" tube thickness and 12" long gives a margin of safety of 830% for steel and 279% for aluminium.
However, no-one in their right mind (IMHO) would brake only using the rear so the force would reduce as more front brake is applied.
I therefore draw two conclusions from the above:
1. There is more than enough strength in a steel torque arm to withstand the compressive loads.
2. I should get a life, try to get out more and re-join the human race.
Of course there is the probability that the above is completely wrong so will happily bow at the feet of those with greater knowledge than I.
Hi Max,
while I commend your research I don't agree with your conclusions.
The number you need is the torque required to very nearly lock up the back brake on a dry road at high speed.
Betcha that's way more than 26 lbs when it's applied at that caliper's mebbe 6" radius and that the torque arm in discussion would fail in buckling way before it reached it's compressive strength limit.
And while we shouldn't disparage their mental state there are those who remove their bike's front brake, we've seen the photos on this site, eh?
while I commend your research I don't agree with your conclusions.
The number you need is the torque required to very nearly lock up the back brake on a dry road at high speed.
Betcha that's way more than 26 lbs when it's applied at that caliper's mebbe 6" radius and that the torque arm in discussion would fail in buckling way before it reached it's compressive strength limit.
And while we shouldn't disparage their mental state there are those who remove their bike's front brake, we've seen the photos on this site, eh?
Max, I like the way you think. Have a look at these:
http://www.xs650.com/forum/showthread.php?p=275313&highlight=Torque#post275313
http://www.xs650.com/forum/showthread.php?p=277512&highlight=Torque#post277512
I'm thinking I better take your conclusion #2...
http://www.xs650.com/forum/showthread.php?p=275313&highlight=Torque#post275313
http://www.xs650.com/forum/showthread.php?p=277512&highlight=Torque#post277512
I'm thinking I better take your conclusion #2...
Hi Max,
check out the compression strut shown in BobbedSled's post #17 in 2Many's second link.
Short and thick does the trick, right?
Max Midnight
XS650 Addict
Apologies the force should read 260lbs.
We can debate the maths for a long time but if I may use a real world example below. which is off a V Max and also fitted to the FJ110 I believe.
It is in compression and as you can see is some 10 1/2" long and just over 1/2" in diameter. The Max is some 100kg heavier than the XS and to the best of my knowledge the do not fail..
I suspect that torque arms of similar length and mounting are pretty common place.
I can't tell how similar the dimensions of the Max item are to the TC Bros item but whilst not suitable for Mr Gmorrone1214's project it would (IMHO) work fine in compression.
If this were not the case then I would assume TC Bros would make that clear?
We can debate the maths for a long time but if I may use a real world example below. which is off a V Max and also fitted to the FJ110 I believe.
It is in compression and as you can see is some 10 1/2" long and just over 1/2" in diameter. The Max is some 100kg heavier than the XS and to the best of my knowledge the do not fail..
I suspect that torque arms of similar length and mounting are pretty common place.
I can't tell how similar the dimensions of the Max item are to the TC Bros item but whilst not suitable for Mr Gmorrone1214's project it would (IMHO) work fine in compression.
If this were not the case then I would assume TC Bros would make that clear?
Hi Max,
I won't argue with your calculation (give or take the odd decimal place) and for sure the Vmax stock strut works OK.
And come to think of it, the XS650 rear disk torque stay looks to be just about the same as the Vmax one.
I based my comments on the gut feeling that I wouldn't be happy using the TC Bros strut in compression unless it's length was shortened by perhaps 1/3rd, that's all.
I won't argue with your calculation (give or take the odd decimal place) and for sure the Vmax stock strut works OK.
And come to think of it, the XS650 rear disk torque stay looks to be just about the same as the Vmax one.
I based my comments on the gut feeling that I wouldn't be happy using the TC Bros strut in compression unless it's length was shortened by perhaps 1/3rd, that's all.
Gmorrone1214
XS650 Addict
Should i Tap the hole in the aluminum slug , or just drill it same diamater and put a through bolt in it?
Hi Gmorrone,
either way will work but I'd feel more secure with a good quality bolt & Nylok nut through the whole assembly than I would when relying on two tapped holes in a piece of aluminum. Especially if I'd tapped them myself, eh?
either way will work but I'd feel more secure with a good quality bolt & Nylok nut through the whole assembly than I would when relying on two tapped holes in a piece of aluminum. Especially if I'd tapped them myself, eh?
Gmorrone1214
XS650 Addict
Yeah I got the bolt and the nut today and also the aluminum rod. Didnt get to mock anything up today.
I have another question for you Fred.
I really wanted to set the caliper up this way.
The 2nd photo is with the caliper adjusted as far up as it can go.
Also that bolt size is prob 5/16 cant remember off hand but not close to 1/2.
I really wanted to set the caliper up this way.
Hi Gmorrone,
like my late mother-in-law used to say "Then want shall be your master."
That 5/16" stove bolt ain't gonna cut it.
Pull those two 12-point reduced head bolts and get a pair that's 1/8" longer.
Now you need to get some work done on a milling machine.
Make an aluminum slab mebbe 1" x 1-1/2" by as long as it needs to reach from the
two bolt holes to below the lower frame member.
Drill through the slab to fit the bolts and bore the holes out to fit the bolts washer heads and leave 1/8" meat to bolt the slab onto the caliper with those !/8" longer bolts.
The aluminum slab will need a tongue on it mebbe 1/2" thick x 1" deep that runs parallel to the frame's axle slot.
Now you need a steel block welded to the lower frame tube that's grooved to fit the aluminum tongue.
The tongue and groove arrangement takes the braking torque and lets the wheel move back and forth to adjust the drive chain tension.
If this write-up ain't as clear to read as I hope, PM me your postal address and I'll mail you a sketch.
member3480
RICH
What you have there looks like it will work as long as you use a sleeve as close to size of bolts. Like I said in the PM there are two different types and as you can see one bracket has to be cutup to fit the other you just have to change shims and make up a stay. Most important is make sure the disk is in the center of the caliber.
