Good Vibrations..

[takehikes]

My reasoning for perhaps dumping the lower and rear through bolts is I stiffened the frame a lot. I plated the area where the hardtail meets original backbone and also between the lower frame rails. The upper is to assist in seat attachment. The lower I’m attaching the battery box to.
Welds are not great but they get ground and then bondo.

 

[BluzPlayer]

I'm with you on that @takehikes.
I will definitely be adding a crossmember (flat plate?) to the bottom which the rear of the motor will be attached to through the rubber motor mount. It should also adequately replace the stiffening provided by the lower through bolt.
The Halco Ascott did away with that bolt as well.

 

[takehikes]

I’ve also thought of maybe just putting thin rubber washers at all the attachment points just to knock down the vibes a bit. Reality is I don’t care. I’m building a chopper. They shake like a dog crapping a rock.

 

[BluzPlayer]

That was my original line of thinking.
I can accomplish that relatively easily.
I wasn't going to use thin washers though.
Maybe 15-20mm thick.
Something similar to the pic attached.
Would involve solid spacing the frame side of the mount to maintain stiffness.
Issue with utilizing horizontal dampening like that has been tested and shows it affects handling through curves especially when flipping from a right hander to a left hander or visa versa.
I'm guessing that is why the Ascott project went with the vertical style dampening locking the horizontal to zero. The design is proven and I decided to follow that path. I would be interested in your results if you decide to pursue the horizontal dampening path.
I also have a hardtail.

 

[Jan_P]

My reasoning for perhaps dumping the lower and rear through bolts is I stiffened the frame a lot. I plated the area where the hardtail meets original backbone and also between the lower frame rails. The upper is to assist in seat attachment. The lower I’m attaching the battery box to.
Welds are not great but they get ground and then bondo.
View attachment 211446

Cant se much wrong with the welds .. Thinking out loud again
There is the possibility to add Cross like an X or so on the stiffener plate should one want that

The front hole is not in a perfect position ( for saddle perhaps ) It sits where the sections reduces ( Bending torque up and down can flex it there )
and is also Heat affected of the welding. Which can crack.
Not knowing the loads .. It is perhaps OK but just mentioning it as input.

 

[takehikes]

Th

Cant se much wrong with the welds .. Thinking out loud again
There is the possibility to add Cross like an X or so on the stiffener plate should one want that

The front hole is not in a perfect position ( for saddle perhaps ) It sits where the sections reduces ( Bending torque up and down can flex it there )
and is also Heat affected of the welding. Which can crack.
Not knowing the loads .. It is perhaps OK but just mentioning it as input.

that hole is for tank mounting nothing more.

 

[BluzPlayer]

Put the frame on the scale.
Just curious before I whack and weld.
49lbs now and I'm sure it will see a net gain.
Already a heavy heifer compared to @gggGary 's
svelte 20lb frame tucked away in the vault of ill repute. Seems like cardboard tubes would weigh more but I'm not a biologist so what do I know.

 

[Tinker Taylor]

Hey Bluz, I came across this thread post that may share an idea with yours; post #114, page 6, Young boy vs Xs650 by LanzSilva.
https://www.xs650.com/threads/young-boy-vs-xs650.55945/page-6
'TT'

 

[fred nurk]

Your name's not ringing any bells. Of course I've had multiple enquiries about XS650 stuff I've had for sale, 99/100 I never heard from them again after they messed me around getting postage costs, wrapping the item up and so on. Which one were you?

gary .. i sent money via pay pal . we organised it over the phone . you didnt except the paypal i sent you... at the time you had 2 sets of carbys . cheers.

 

[toglhot]

Wrong, I went to the PO, purchased packaging material, got a price on postage, packed the carbs ready to post, but I never heard from you again. How many other people's time have you wasted? FYI, when someone deposits funds in your paypal account, you don't get to accept the funds or not, the funds are there. In all this time you have not rung, or emailed. You are full of shit!

 

[BluzPlayer]

Thanks @Tinker Taylor .
I think @LanzSilva was using those rubber bushings for the steering dampening. Still the same principle.
I have decided to go a different direction than I initially envisioned. I will be following a similar path that was utilized by Trigg in his collaboration with Yamaha that resulted in the Ascott TT. It will require more modification than my original plan but is a proven concept.

 

[5twins]

You need to check the engine mounting bolt torque from time to time. When I got my '78, not just one but ALL the engine mounting bolts were loose, lol. The long bottom one also had apparently broken and had some "generic" replacement installed. Luckily, the bike came with a N.O.S. replacement the previous owner never installed. I don't know why, or even if it's true, but one of the manuals stated that vibration would be reduced if the motor mounts were tightened in the order shown .....

The mounting bolt torque values are something Yamaha changed over the years, and I don't like some of them. In particular, the near doubling of that long lower bolt value, to 65 ft/lbs. Maybe that's why the original on my '78 broke? I like and use the '77 specs.

 

[BluzPlayer]

Thanks for the information @5twins .
Very interesting and I would think very useful for most everyone.
Odd that 4 of the mounting point's values were reset to the middle of the previous range while that one lower bolt value nearly doubled.
Seems like great advise to check those values as well as retorquing all the points in the correct sequence. Perhaps something that many don't think about.

 

[toglhot]

This from Fred Nurks:

'went back through my paypal turns out i had your email name wrong i had "toglehot" looks like you dont have an e in your name.. thats what happend..'

Sorry to go off topic, blame Fred Nurk!

 

[toglhot]

I must be a one off: I've never used a torque wrench for anything except cylinder heads. The only thing that ever came loose was the manifold on a Triumph 650. Silly me replaced the studs and locking nuts with ordinary 1/4" whitworth bolts, no spring washers. Cost me two holey pistons!

 

[takehikes]

You need to check the engine mounting bolt torque from time to time. When I got my '78, not just one but ALL the engine mounting bolts were loose, lol. The long bottom one also had apparently broken and had some "generic" replacement installed. Luckily, the bike came with a N.O.S. replacement the previous owner never installed. I don't know why, or even if it's true, but one of the manuals stated that vibration would be reduced if the motor mounts were tightened in the order shown .....


View attachment 211781

The mounting bolt torque values are something Yamaha changed over the years, and I don't like some of them. In particular, the near doubling of that long lower bolt value, to 65 ft/lbs. Maybe that's why the original on my '78 broke? I like and use the '77 specs.

You know looking at this ……the order and the torque values make it fairly clear that I was discounting the lower bolt in error. Looks like the three lower/rear mounts are key. At least for rigidity. Top one looks like a waste. Front looks like it’s mostly for locating the engine in the frame. That bottom one now looks key to keeping the tubes aligned. Question is which ones arethere for the engine and which for the frame?

 

[BluzPlayer]

Hey @takehikes .
I'm not certain of the interpretation.
From what I think I've learned from geometry and real world experience it seems that a triangle provides strength. In fact the triangle is the strongest of all geometric shapes. Looking at the front mount (#1 in @5twins diagram); the top mount (#2 in the diagram); and the top rear mount (#3 in the diagram) and drawing a line between those points you will see a triangle.
The strongest triangle is an equilateral triangle where all side are equal. The triangle observed by connecting those points in the drawing is very close to an equilateral triangle. Not precise but measuring those legs show it is close enough.
That would be an indication to me of triangulating the frame for strength.
Utilizing the front mount, the rear mount, and the lower mount (1,3,5) also makes a triangle.
However the triangle formed is not as strong and would appear to my (no degree in engineering) eyes to have less effect on the frame rigidity.
As you said, there are two different issues that are affected by these choices.
Those that influence frame rigidity and those that are required for the motor to be solidly mounted.
Optimally there will be a marriage between the two. I would love to see some testing with vibration measurements (using an app that utilizes a smart phone's accelerometer) but unfortunately I can't take them. Although my initial intent was to take these measurements before and after modifications; the new direction I am pursuing (Trigg's Ascott style mods) will require too much frame modification for that to be possible. I will still do the after testing but those numbers will not be comparable.
Perhaps I can get some numbers from the sample size at the Ozark rally if the members are willing. That would be optimum as all the data would be taken across a spectrum of bikes with the same device. These measurements would be in the existing setup of each individual bike. No modifications or removal of bolts.
As is with whatever countermeasures are or are not being employed by the owner.
We will see.

 

[takehikes]

Hey @takehikes .
I'm not certain of the interpretation.
From what I think I've learned from geometry and real world experience it seems that a triangle provides strength. In fact the triangle is the strongest of all geometric shapes. Looking at the front mount (#1 in @5twins diagram); the top mount (#2 in the diagram); and the top rear mount (#3 in the diagram) and drawing a line between those points you will see a triangle.
The strongest triangle is an equilateral triangle where all side are equal. The triangle observed by connecting those points in the drawing is very close to an equilateral triangle. Not precise but measuring those legs show it is close enough.
That would be an indication to me of triangulating the frame for strength.
Utilizing the front mount, the rear mount, and the lower mount (1,3,5) also makes a triangle.
However the triangle formed is not as strong and would appear to my (no degree in engineering) eyes to have less effect on the frame rigidity.
As you said, there are two different issues that are affected by these choices.
Those that influence frame rigidity and those that are required for the motor to be solidly mounted.
Optimally there will be a marriage between the two. I would love to see some testing with vibration measurements (using an app that utilizes a smart phone's accelerometer) but unfortunately I can't take them. Although my initial intent was to take these measurements before and after modifications; the new direction I am pursuing (Trigg's Ascott style mods) will require too much frame modification for that to be possible. I will still do the after testing but those numbers will not be comparable.
Perhaps I can get some numbers from the sample size at the Ozark rally if the members are willing. That would be optimum as all the data would be taken across a spectrum of bikes with the same device. These measurements would be in the existing setup of each individual bike. No modifications or removal of bolts.
As is with whatever countermeasures are or are not being employed by the owner.
We will see.

i agree triangulation matters. I grew up in the chopper world and saw the engineering that went in to the frames. I also know we dealt with paint shaker engines and never had this many mounts. I suspect they we trying cover every base and over did it. This thing is going to shake by design so maybe forget about it and only worry about chassis stiffness.

 

[BluzPlayer]

Well that is certainly the common approach.
Personally Iif I weren't going to follow the plan used in developing the Ascott TT; I would still try my original plan of action using the horizontal dampening which could could be attempted without any frame modifications; thus being reversible. Testing the combinations could create a guide to finding a solution when combined with other countermeasures (primarily a well balanced engine and a crankshaft without runout). It is worth noting that Trigg's mods on the Ascott utilizes only 3 motor mounts.
The front, the top, and the rear.

 

[takehikes]

On the drawing and eyeballing mine 1,2,3 look same length triangle as 1,3,5 which may be why I’ve seen a number of bikes without that upper mount.
I always thought the front mount was just awful. So I sawed mine up and did this…. Not as stiff but prettier.