The BSA A7-A10 Forum

Technical => Frame => Topic started by: Tone on 09.06. 2009 18:30

Title: Swinging arm
Post by: Tone on 09.06. 2009 18:30
Hi All, Is it possible to do the pivot pin and bush on an A10 swinging arm, only the haynes manual says you need all sorts of special equipment is this right?
Title: Re: Swinging arm
Post by: RichardL on 09.06. 2009 19:05
Tone,

Before undertaking this, you should decide if you have a good reason to change the "Silent Block" bushes (as they are called), as they are not easily subject to failure. I'll leave it to others here to say if they have had to replace any just for service. As for myself, I was changing from solid spindle to hollow spindle and was forced into the job. I can tell you that I thought it was the Job From Hell. First, I used a Sawzall to split the steel sleeves, as close as I could get to the swingarm I.D. without cutting that. Then, since things still weren't moving, I torched out the rubber. (Not a "green" endeavor. Remember, I am not the one suggesting you do this under cover of darkness.) Then, I was finally able to prise out inner and outer steel sleeves. Then, the new bushes were a bit too large to fit the I.D. of the swingarm, so I ran my cyclinder hone in there for about an hour. Then they seemed about to fit, so I contrived a press made from 3/4" diameter all-thread and some really big nuts. Using about a 22"-long breaker bar, I proceded on one of the sweatyist, most tedious nut turning processes I never wish to repeat. Yes, the bushes got a little deformed on the ends from so much pressure, but not so much that they couldn't be cleaned up. Then, I discovered that the inner sleeves of the two bushes were a bit out of alignment and the spindle would not pass through. Then, I bought an adjustable reamer on eBay to run down through the two spindles to get them to line up well enough to get the spindle through.

So, in answer to your question, "Sure, they can be replaced with no problem!" Seriously though, other folks reading this will, no doubt identify where I went wrong so you don't have to.

Richard L.
Title: Re: Swinging arm
Post by: bsa-bill on 09.06. 2009 19:57
There are bushes out there that are a tad too big, I had to give up on them as they were going to distort to much.
Ordered some from C& D and they went straight in without problem ( this was about ten years ago )

All the best - Bill
Title: Re: Swinging arm
Post by: A10Boy on 09.06. 2009 20:11
You might just make sure the SA spindle is tight enough, if its loose, it can move around.
Title: Re: Swinging arm
Post by: RichardL on 09.06. 2009 20:23
Yep! "Tad too big" describes it. Wish I had known at the time. As for spindle fit, it seemed OK when I was done.

Richard L.

P.s. No intention here of swiping the thread from Tone.
Title: Re: Swinging arm
Post by: Tone on 09.06. 2009 20:37
Would the bushes be worn as well as the pin , or could you just change the pin?
Title: Re: Swinging arm
Post by: BSA_54A10 on 10.06. 2009 11:23
If the pin is worn the the bush is worn as the pin is not supposed to move on the bush, that is what the rubber is there for.
My rule of thumb is if I can remove the shock absorbers and the bike dose not fall down the the rubber has hardened and needs to be replaced.
IF it dose fall down then you can ream the bush and fit a "speedy sleeve" on the shaft as the rubbers is still OK.
Yes it is neither clean nor fun.
Like any bush/ bearing things will be a lot easier if you cook the hole and freeze the bush.
thirty minutes in a hot oven will work wonders as will chilling the bush ( on its shaft or insertion device ) .
Do one side let it warm up remove the shaft then repeat for the other side.
If you can get your hands on it chilling the bush in dry ice is a lot better than just sticking it in the freezer over night.
Do not use liquid nitrogen as that is cold enough to make the rubber quite brittle.
Title: Re: Swinging arm
Post by: MikeN on 10.06. 2009 11:35
Tone,
  Manosound is right ,Its a horrible job.I did mine slightly differently I used a big hydraulic press and some suitably turned up mandrels .It took several hours (and tons) and it fought me all the way.
  I did mine because i wanted the frame and s/a powder coated and was advised the rubber would not like the high temp involved.
  Then my neighbour immediately asked me to do his, which pleased me no end!
  I wont be doing another one .
  re. your last message,the pin and bushes should not actually wear if everything is set up corerectly because there are no  bearing surfaces involved.Just a twisting of the rubber.
  But the rubber will deteriate with age and oil contamination.
  Has any other m/cycle company used this method before or since I wonder?
Mike
Title: Re: Swinging arm
Post by: RichardL on 10.06. 2009 11:54
Gents,

Swingarm and bushes rotate around spindle, else, no swing in your arm.

Richard L.
Title: Re: Swinging arm
Post by: MikeN on 10.06. 2009 12:26
Sorry Richard but I dont think thats correct,
  The bushes should not rotate around the spindle.
  The spindle is there to clamp the inner tubes of the bushes hard to the side plates on the frame and to each other so they dont rotate  (as well as stopping the back end falling off) .
 The outer part of the bush rotates with the s/arm .
  The swing in your arm is obtained by the twisting of the rubber in between.
Mike
Title: Re: Swinging arm
Post by: Brummie1960 on 10.06. 2009 14:20
Hi,

That's something new I've learned, I also assumed the arm spindle pivoted around the bush.
In the parts book it just shows a plain cylindrical bush, no sign of any rubber.

I have just degreased my swinging arm and found the remains of some rubber around the ends of the bushes, but it was breaking up. I plan to have the swinging arm powder coated, so is it best to remove the old bushes beforehand, or leave them in place then remove/replace after power coating?

Nigel.
Title: Re: Swinging arm
Post by: MikeN on 10.06. 2009 14:55
Nigel,
  The powder coater I use is "Vulcan Enamellers" in Rustington on the south coast.This is not much use to you I realise.
  Anyway,he informed me that he coats at a temp of 200-250deg C and reckons that it would not do rubber parts any good.So I advise you to remove them.
  tell your powder coater and he will put his bungs in the bores .
  The potential problem with p/ coating is that if it gets damaged and moisture gets underneath then corosion will start and it spreads ,lifting and bubbling the coating off as it goes. My cheap swing-seat in my garden is a good example of this.
 However, Vulcan always shotblast parts, Then they phosphate dip them which is a rust resisting process,then I always pay a bit extra and he zinc powder coats them before gloss powder top-coating.
  The zinc is supposed to be the ultimate rust proofing (he tells me) and it also helps to give a deeper luster to the top coat.it also fills slight pitting (You cant use filler with p/coating).
  So check with your man to see if he does any or all of the above.
  Ive had  8 bikes done now by Vulcan and have always been pleased with the results.
 Mike
Title: Re: Swinging arm
Post by: RichardL on 10.06. 2009 16:17
Mike,

Without blatantly disagreeing and exposing myself as a silly fool, I am having a very hard time envisioning how the quite thin layer of rubber can be twisted to the angular extent available for swingarm movement. Also, I am having an equally hard time envisoning getting the spindle to be tight enough in the inner sleeve to force the movement only in the rubber while also allowing for the spindle to be inserted and extracted, when need be. Bear in mind that heating the swingarm with the bushes in place, such that expansion allows spindle insertion or extraction, would have been just as impractical in 1955 (my  model year) as it is now.

Adding this point a bit after posting, I believe the rubber might just be there to avoid feeling every pebble in the road via the swingarm.

So, do we need a vote, or am I out by summary judgement?

Richard L.
Title: Re: Swinging arm
Post by: bsa-bill on 10.06. 2009 16:46
Richard my project had the spindle seized solid in the bush, had to cut the spindle with a very thin cutting disc in between the sw/a and the side plate, the bushes were also seized into the sw/a, but the sw/a did move up and down, seems impossible but it did.
Removal was a case of drilling the rubber bushes out from both sides then forcing the inner tube out with a length of threaded rod big washers, sockets and well oiled nuts.
The outer bushes were cut with an air tool pad saw thingy then collapsed into themselves using small chisels, does'nt really matter if you cut through the outer sleeve into the sw/arm a little bit, once you get them collapsed a bit they will knock out from the opposite side of each sleeve.

The laws of physics may not always apply to A10's ( Jim)

All the best - Bill
Title: Re: Swinging arm
Post by: RichardL on 10.06. 2009 19:29
Bill,

That sounds more like rust and corrosion than intension on the part of BSA. I doubt that their service manual read, "To service the swingarm spindle and bushes, start by cutting off the end of the spindle with a cutting disk that will be invented some time in the future."

I am still not ready to accept the frozen-to-the-spindle answer. Perhaps the term "Silent Block" referes to sound deadening of road noise by virtue of the rubber. After all, they are not called "Bounce Blocks" or "Swing Dampers" or the like.

Richard L.
Title: Re: Swinging arm
Post by: bsa-bill on 10.06. 2009 19:46
Yes it was rust and corosion, my point was that even with the spindle siezed the sw/arm still swinug (via torsion on the rubbers),
Come to think about it quite a few bikes and car used rubber torsion for suspension

All the best - Bill
Title: Re: Swinging arm
Post by: rocket man on 10.06. 2009 19:47
hi you could go to the bsa super rocket site they tell you howe to remove
the silent blocks
Title: Re: Swinging arm
Post by: rocket man on 10.06. 2009 19:50
heres what they say Separating the swing arm (and removing the silent bloc)
The swing arm on an old A10 does not come apart easily. It is held together by the swinging arm fork spindle (42-4362) running through the center of the swing arm. This spindle is held in place by a securing bolt on one end and a nut on the opposite end. I used the following technique successfully for removal of this swing arm:

- remove the bolt on one end of the swing arm and loosen the nut on the other end

- run a piece of continuously 7/16" threaded rod through the holes in the plate on each side of the frame above the spindle, place nuts and washers on the inside of the plates

- torque the nuts outwards to apply a slight pressure on the two plates at each side

- Drive the nut with a hammer until the spindle breaks free

An attempt to drive the spindle out should be made before doing any jacking of the frame to minimize potential impacts to the frame (I have only had to resort to drastic measures like above in one instance). Additionally pry bars and a blow torch may possibly be used for this procedure before attempting to use a jack to force the frame apart (I have never tried the pry bar/torch technique).

Once the swing arm is separated, the inner housings (or silent blocs #42-4662) around the spindle can be removed and replaced if necessary. In my case, I had to remove the silent blocs to prepare my frame for the thermal portion of the powder coating process (to prevent the rubber part of the silent block from catching fire when the powder coating was baked to the frame). There are two silent blocs within the center of the spring arm. These silent blocs are tubular and consist of a rubber spacer sandwiched between a metal inner and outer shell. The rubber spacer and outer shell are half as long as the inner shell (which runs all the way to the center). While the silent blocs could potentially be pressed out (I did not have sufficient equipment to try this approach), I had to use a more destructive removal technique. I was able to successfully remove my silent blocks by torching out the inner rubber. The outer metal shell did not come out as easily after torching the rubber.

If difficulty is encountered with removal of the outer metal shell, a Dremel tool with a 24 inch flexible shaft and a cutter bit can be used to cut one slot along the length of each bushing.

Once the bushing is cut, a long steel rod can be used to knock each bushing out (driving from the opposite side). Note: I forgot to take this outer shell off my swing arm prior to powder coating (which complicated outer bushing removal and caused scratches to my new powder coating when I tried to get it off).

To put the new silent blocs in, a press can be used or, if you are like me and can't afford a press, than a long piece of continuously thread rod can be run through the center of the bloc and swing arm with washers and nuts at each end to draw the silent bloc into the swing arm. In my case, I found that a 3/4 inch threaded ROD (with nuts) used in combination with two 3/4 inch washers and two 1 inch washers was needed to do the job properly. The inner metal shell of the silent bloc is designed to protrude slightly and is not level with the outer metal shell. To prevent the inner shell from taking any torque, on each side place one inch washer around the inner shell (it fits perfectly), than the 3/4 inch washer, followed by the nut. This method forces all the torque on the outer shell. 
Title: Re: Swinging arm
Post by: MikeN on 10.06. 2009 22:01
Hello Richard,
  Bill has remarked that his s/arm had the bushes rusted to the spindle.
 Clearly it is not supposed to be rusted.Although it doesnt matter because it demonstrates that it does not affect the correct functioning of the joint, as he found out.
   If he decides he wants to take up moto-crossing and fit longer than standard rear shocks, then they probably would tear out the centres of his bushes.I believe that some off-roaders fit coventional bronze bushes for this reason.
  Im not saying the system relies on the spindle being a very tight fit in the bores .Im not saying its even a very good system.
   The way it works is ,If you look at the bushes you will see that the inner core is slightly longer than the outer .
  This allows the 2 inner bushes to be clamped ENDWAYS between the frame plates when you do up the centre spindle (which should be a nice slide fit).So preventing rotation.If yours rotate then the ends of those thin tubes are wearing away your frame
  You have 4 other joints on your bike that work in exactly the same way at each end of your shock absorbers. They dont revolve on their fixing bolts (I hope).
  Consider this.
 a)The centre part of the bush is made from a soft steel,the spindle is made from   (hopefully)high tensile steel.This is not a good choice for bearing materials.
b)How is one supposed to keep it lubricated, there are no grease points or instructions for maintenance in any manuals.
c)What is supposed to control sideways movement ? There are no thrust washers .If it is as you say then the s/arm would slide laterally and rub on the frame side plates.

Also as Bill states plenty of cars used rubber in torsion for suspension .Thinking about it ,My old Austin A35 used this method somewhere in the front wishbones.
  Cant think of any other  bikes though .
Speak again,Mike



Title: Re: Swinging arm
Post by: RichardL on 10.06. 2009 22:33
Mike,

Thank you for an interesting explanation, and it almost had me, but then I thought: why not continue the debate just for fun? I'm guessing you and others are still amused rather than p*ssed off.

So, Roland Pike says to the engineering team, "Boys, what we need is 90 (or so) sq. mm of surface between the frame flange and the inner sleeve of this rubber sandwich so that the frame flange will twist the entire length of rubber in the sandwich, thereby damping vibration from the swing arm."

My point being, I don't think there is enough friction between the inner sleeve and the frame flange to cause the rubber to twist, rather than the sleeve just slipping on the metal-to-metal contact. I'm thinking, grease the spindle like any other surface that requires infrequent lubrication (as in permanently sealed wheel bearings) and let the swingarm move on the spindle and, if it so happens, wear against the flange up to the force available from the resistance of the rubber. The slow and minimal-arc rotation of the swingarm is not going to heat the grease to even within the same universe as its breakdown temperature, and the grease really has nowhere to go, and if it does, it's not that big a deal. It will be just like when someone who thinks no grease is needed tries to remove the rusted-in-place spindle.

Richard L.

 
Title: Re: Swinging arm
Post by: trevinoz on 10.06. 2009 23:10
Richard, you are wrong, wrong, wrong! The rubber definitely twists, a small amount at the bush becomes a large amount at the end of the swinging arm.
I have dismantled some with the inner solidly rusted to the spindle and the outer never having moved in the swinging arm. I have actually had to cut the spindles on some.
I have had others with loose nuts on the spindle and the frame was badly worn where the spindle moved in the frame and deep grooves were worn in the side plates where the ends of the bushes were moving.
My Norton Atlas has the same set-up, I couldn't remove the spindle as it was frozen solid so I left it alone, making sure the nuts were tight.
Trev.
Title: Re: Swinging arm
Post by: RichardL on 11.06. 2009 02:17
Help me, Clarence, I want to live! *dunno2*   *grins*

(I'll be amused if Brits or Aussies know the reference.)
 
Title: Re: Swinging arm
Post by: Brian on 11.06. 2009 02:41
Nup, got me. The only Clarence I remember was a crossed eyed lion !!!!!!!!!!!!
Title: Re: Swinging arm
Post by: MikeN on 11.06. 2009 08:25
Richard,
  I agree with the last point you made.
   There is not much metal to metal area of contact to do the gripping and frankly, i think its an engineering abomination.

  But thats how its supposed to work and we're stuck with it!

Mike
Title: Re: Swinging arm
Post by: BSA_54A10 on 11.06. 2009 12:33
Well considering that most silent blocks are in the order of 50 years old, sound like BSA got it right to me.
Also consider that even with trashed silent blocks the bike still runs and handles quite well.
Try riding a modern bike with a loose tapper roller, let alone a trashed one.
If you pretend that the swing arm is a proper triangle and use the length of the swing arm as the base and 4" ( movement in the shocks ) as the height then you can use the trig functions on your kids calculator to work out that the swing arm rotation is some thing like 8 deg.
They are a total pain to do but it some thing that only gets done once every 50 years so it can be tollerated.

Now as to powder coating there is about 100 different types.
If done properly then it is tougher, stronger and more corrosion resistant than the original paint.
OTOH if it is the "melted plastic" then it is a recepie for disaster.

The original powder coating was in fact a fully vitrious enamel that chemically bonded to the oxadized surface FeO ( mill scale ) not Fe2o3 (rust) and was impossible to remove once in place.
The newer cheaper stuff is just finely a ground thermoplacstic plus some pigment. Good fro cheap out door furnature, not good for motorcycle frames.
Title: Re: Swinging arm
Post by: coater87 on 11.06. 2009 13:34
  Hello,

 While we are on this swing arm subject, I also knew I had to replace my bushings. The right hand bushing feels like its either missing, or too far into the swing arm and that side is very sloppy on the spindle.

 I went ahead and ordered a new pattern pin, and silent blocks. I have not even tried to remove the old yet, but I did do some measuring. The new pin measures .811, and the inside of the bush measures out at .803. I understand these should be a press/jam fit, but that seams like a lot of difference to make up. Does that sound about correct, or are these pattern pieces a little off? I am worried I will peel back the threads quite a bit- should I ream the bushes to say .808 or some such?

 To see if I have this correct, there is a slight bit of the inner bush that sticks out, these little bits are supposed to fit into the frame plates- the larger outer bush should be flush with the swing arm itself. Then you would spread the frame a little, seat the swing arm and try to install the pin. Now one end of the pin has a cam lobe shaped piece of metal, when this is turned just so a hole in this piece lines up with a small hole in the frame plate. Should I try to get these small holes to line up with the swing arm level to the ground- or is it just coincidence that these holes line up at all and maybe the one in the pin is for a spring to hook to or something? Kind of confusing back in this area.

 Thank you,
Lee

 
Title: Re: Swinging arm
Post by: RichardL on 11.06. 2009 14:36
Lee,

The pin in question does go into the frame plate and, though no one has mentioned it, it does give creedance to the tight-pin-twisting-rubber theory, as much as I hate it. Now, I'm not sure, but I take it from a previous post that the protrusions rub on end and not circumferentially. If the latter, it would, as you say require spreading the frame. That seems odd and perilous, considering the nearby crossmembers.

As to pin diameter, you are welcome to borrow my adjustable reamer if you need to enlarge the inside sleeve. As for my own bike, I am perfectly comfortable riding in ignorant bliss with a slip-fit spindle.

Richard L.
Title: Re: Swinging arm
Post by: RichardL on 11.06. 2009 16:40
I just made a phone call to SRM to hear their position regarding the Silent Bloc bushings. (Not that I didn't believe every one of you, faithfully, trustingly and invariably.) First question: should the spindle be a press fit or a slip fit? Answer: "Slip fit." Second question: is the swingarm supposed to rotate freely on the spindle?  *conf* Gulp!  *conf* Answer: "No." Third question: is the force on the the inside sleeve from end pressure or circumferential (I'm not near my bike to know if this is obvious)? Answer: "End pressure." Forth question: then, you shouldn't need to spread the frame, right? Answer: "Not if the bushes are meeting properly at the center, however, it can be a fiddly job."

So, I guess I must acede to the throngs. I now think that the necessary force to make this work (if, indeed, it does) comes from pushing at the outside with the force of the tightened nut while the inner sleeves meet at the center to affect enough frictional force to matter.  

I have an acoustics-based discussion on this that must wait until I have time.

Richard L.
Title: Re: Swinging arm
Post by: bsa-bill on 11.06. 2009 16:55
Not sure about the last bit as the SW/arm has a stop midway so the outer sleeve meets up with that.
Same thing really as the rubber would transfer pressure

On the subject of rubber torsion suspension was it not Greeves that used on the front suspension with leading/trailing link

All the best - Bill
Title: Re: Swinging arm
Post by: RichardL on 11.06. 2009 17:07
Bill,

Look at the long extensions of the inner sleeves toward center.

Richard L.

I hate this. Am I now making the twisting rubber arguement?
Title: Re: Swinging arm
Post by: riflegreen on 11.06. 2009 21:17
The inner sleeves pass right through the rubber & abut to each other in the middle , the outer sleeve is a press fit in the swinging arm .

The outer ends of the inner sleeves are tight to the frame and are clamped tight by the spindle . Before tightening the spindle the swinging arm should be moved to roughly half travel and then tightened to clamp the bushes , this gives the correct torsion to the metalastic bushes .

If this is not done and the bushes move round the spindle you will get wear in the frame and wear in the bush ends .

Eventually makes a very wobbly ride .

Chris
Title: Re: Swinging arm
Post by: bsa-bill on 11.06. 2009 22:14
see what you mean Richard but I'm sure the sw/a tube is stepped, however my memory is suspect since I had heart op last September, this forum does help though

All the best - Bill
Title: Re: Swinging arm
Post by: RichardL on 11.06. 2009 22:30
Riflegreen,

Great comment and welcome to the forum. The aspect of tightening at the half-travel point is not one I considered when assembling my bike (given the fact that I thought it was just free pivoting) and has not been mentioned here previoulsy, as far as I can recall.  

Since I am newly brainwashed into the torsion rubber theory, two questions come to mind, springing from your comments.

1. Would it be better to loosen the spindle nut and sit on the bike with the shock absorbers attached, then, use that as the tightening point for the spindle? Would this not provide a better half-travel point?

2. Is it possible that the squeezed-tight friction fit, either intentionally or fortunately, has limitied friction where the outside portion of the inner sleeves makes contact with the frame plates? It seems this would result in slippage under duress and might serve to protect the, as you say, "melalastic bushes." Then, when back closer to the half-travel point, the friction is still enough to afford normal short-arc movement.

Any comments are welcome and will certainly be an education for me.

Richard L.

Title: Re: Swinging arm
Post by: RichardL on 11.06. 2009 22:32
Bill,

I find that riding does require a lot of attention to the ride itself, but destresses me because I don't think of things like work, home improvement, family squabbles, et cetera.

Richard L.

Title: Re: Swinging arm
Post by: trevinoz on 11.06. 2009 23:37
Richard, have a look at your shocks and see how little they actually move.
When fitting the swinging arm, I leave the spindle loose and fit the shocks then tighten the spindle. Works for me.
Aren't you lucky there are so many people willing to correct your misguided ideas?
Trev.
Title: Re: Swinging arm
Post by: coater87 on 12.06. 2009 03:11
 OK,

 So the bush just gets crushed up against the frame plates? Should the hole in the plate be the same size as the pin, or bigger?

 Looking at mine, the frame plate hole is quite a bit bigger, and this is whats giving me the slop. Do I need to weld this shut then re-drill to the correct size- or maybe that little bit of slop is supposed to be there to line up the swing arm and the nut is what keeps everything in place?

 I have no idea.

 Lee
Title: Re: Swinging arm
Post by: trevinoz on 12.06. 2009 05:38
Lee, it should be a close fit. Weld and drill or file.
Trev.
Title: Re: Swinging arm
Post by: MikeN on 12.06. 2009 08:49
Lee,
  Just to complicate it a little.
   There are 2 diameters of pins available(and silentbloc bushes to match).The first s/arm models had rod operated rear brakes.When they chaged to cable operation BSA introduced the cross-over shaft which required a larger diameter pin.When the Rocket Goldstar came out it reverted to the smaller pin.
  You say your frame hole is quite a lot bigger so you may not have the correct pin . If you dont wish to purchase a new pin the best way to rectify is to have some reducing bushes made up to make sure the holes stay concentric.
 However, If the oversize hole is due to wear in the frame then it might be better to repair, as you say with welding and re-drilling.
 Mike
Title: Re: Swinging arm
Post by: bsa-bill on 12.06. 2009 11:08
Hi Richard - yes up here the procedure was to get a prospective girlfriend to sit on the bike ( bike off the stand) and tighten the spindle at that pint, of course at a later date you may have to repeat the procedure with nieghbourhood fat lass to get it right *lol*

and on the other point re stress the more I get at this project ( and rob bits of my was roadgoing bike ) the further I get from riding, now the gearbox does'nt want to shift properley, I'm at a standstiil now due to pains in my legs and thighs Doc talks about muscular something or another also got three screaming grandkids staying, cant find a way to make them unhappy, tell them to be quit and they just smile and continue - why me

never mind there's a better day coming

All the best - Bill ( sorry for the downer you got me on a bad day)

Title: Re: Swinging arm
Post by: riflegreen on 12.06. 2009 11:15
Hi All ,

Spose I should have introduced my self , ex Greeves Comp Dept , Guzzi , Ducati , Suzuki , MZ , CCM , Yamaha & and anything else that came into the dealers .

Currently have two Goldstars , an A7 and a pre war single .

The idea of metalastics is to give torsion to the swinging arm etc that they are fitted to , yes, sitting on the bike then tightening the spindle will give the same effect and is probably not far from half movement . Preloading the bushes applies to any make of bike that has them .

Don't forget that the swinging arm pivot being the pivot point has very little movement compared to the wheel/damper end .

The spindle should be a sliding fit in the frame mounts , too much slop can make the wheel/swinging  lay at an angle relative to the frame .

The same applies to the solid spindle arm & the hollow spindle later frames .

It is not uncommon to see large washers brazed on the outside of the frame mounts to repair worn holes but drilling oversize and fitting spacers looks much neater .  

Far as I recall the tube that the bushes fit into is parallel right through .

I think most of the Goldstar parts suppliers sell spacers to convert the hollow spindle frames to solid type , these could be used to repair damaged arm mounts .

The only danger when drilling out the frame mounts to repair them is not getting them in line bit like repairing the center stand lugs when they wear out through lack of grease or the nuts being loose .

Chris
Title: Re: Swinging arm
Post by: LJ. on 12.06. 2009 14:22
Hiya Chris! Nice to have you join us, I should have recognised 'riflegreen' Thanks again for the tool box... We must catch up again soon eh? mean while... I'm outta this thread, dont wanna get into doing swinging arm bushes yet.  *eek*

Cheers
LJ.
Title: Swinging arm ... RGS more Questions
Post by: 69Bonni on 12.06. 2009 15:19
Hi and Welcome Chris!

Blast!!! i just as i thought! the solid spindle is a different dia to the hollow type. Now wouldnt it just have been easier to have the same holes in the frame and and use a bigger Dia solid spindle.

All this buillding RGS is getting to be a pain! So i have my single sided hub, and my chain guard, my brake pedal and although the single sided hub will fit the swing arm, the swing arm doesnt have the right chainguard mounting or the Torque arm mounting. Im begining to think it may be easier to Modify the swingarm than change it for a B31 / SS hub type.

Quandry, if i fit a B31 swing arm i have to mod the frame too and it have bigger holes for the hollow tube.
Maybe i just machine up a solid spindle the Dia of a Hollow spindle or Machine up a dummy spindle the same Dia as the brake cross shaft with some end plats on to look like a solid, and Modify the swing arm.

Does the Board think i could use a clamp on Torque arm mounting on the swing arm obviously a substantial one. Sounds tacky doesnt it dont like the idea maybe i will change that swing arm after all.

Any views appreciated

Steve
Title: Re: Swinging arm
Post by: riflegreen on 12.06. 2009 15:36
Hi Steve ,

You have to remember that the RGS used a lot of GS cycle parts and these were all based on the first s/arm frames of 1954 .

If you alter your s/arm to GS/RGS type and fit a solid spindle you need to fit the rducing spacers in the frame. Have you got the rear set rest mounts in the frame loops ? , if so then Eddie Dow recommended using the footrest as the brake pedal fulcrum - saves welding a brake mount on .

Lots of the replica RGS have the full width swing arms with all the bits cut of and the single sided hub brackets welded on .

Takes dedication to make even a proper replica RGS ( and a deep pocket ) *smile*

I've just sold an A10 frame with all the right bits on ( 1954 ) and was suprised to get £500 for it .

Chris
Title: Re: Swinging arm
Post by: RichardL on 12.06. 2009 15:46
Steve,

In adpating my post-'55, hollow-spindle-type frame to work with my left-side-pull half-width brake, I bought a hollow spindle and the associated bushings with the larger diameter. That is from whence my tale of bushing replacemnt woes originated. I plan to put rubber plugs in the spindle openings when I remember to do so.  

Further torturing the twisting rubber topic, it just occured to me that the metalasitic bush was designed well-prior to the design of the hollow spindle. The bushes for solid spindles had thicker rubber to stretch than those for the hollow spindles. Does anyone believe or know for certain that BSA did the math or the tests to determine that less rubber would stretch adequately? Does anyone care, or am I just an obscessed frustrated, wanna-be motorcycle engineer?

Richard L.
Title: Re: Swinging arm
Post by: riflegreen on 12.06. 2009 15:52
Richard ,

I suspect BSA looked at all aspects of the different size metalastics , they certainly did at Greeves when they went fron a 3/8" spindle to a 1/2" and then 5/8" .

Metalastics are also available in different grades of rubber , there were four different grades for Greeves front forks for road , trials , mot cross and r'racing .

Chris
Title: Re: Swinging arm
Post by: riflegreen on 12.06. 2009 15:56
Steve ,

If you modify your existing s'arm and use the hollow spindle then you won't have to change the metalstics - big bonus .

Most metalastics look a bit raggety at the open end  but as they are quite long it is unlikely that the rubber has degraded further in .

Chris
Title: Re: Swinging arm
Post by: 69Bonni on 12.06. 2009 16:13
Hi Richard and Chris

Yes i think that all those tails of Woe are enough for me, I did the A65T and that was a bit of a pig.
I think i might modify it, i would weld it but the swing arm has already been powder coated / stoved by the previous owner, I'll take a closer look at the torque arm.

It will save me looking for a new swing arm anyhow!

Many thanks guys

Regards

Steve
Title: Re: Swinging arm
Post by: riflegreen on 12.06. 2009 16:16
Steve ,

Have you got the rear set mounts fitted ? .

Chris
Title: Re: Swinging arm
Post by: 69Bonni on 12.06. 2009 16:25
Hi Chris

No i dont have rear sets mounted, im building it as a tourer

Steve