Motorbike question...

[AdeV]

....I'm not a motorbikist by any stretch of the imagination.... but someone's asked me to turn up what is, I think, a swing arm support; at least, it has a bunch of bearings on it & is bolted end to end. He wants it 28mm OD for most of the width, with a ~25mm section turned down to 20mm, and central 17mm bore all the way through.

The question is, what should I make it out of? The customer reckoned just boggo steel; I'm not sure whether to use stainless or not...

Any ideas from the two-wheeled fraternity as to what would be a sensible choice?

I can draw a C-o-C if required.

[Jonny]

Do you know if its using a through bolt or not?
ie long bolt and thread or nut at the other end.
How long?

Some wheels have a steel floating insert to reduce the flex of the through bolt with the bearins pressed in to the aluminium or magnesium.
Most swing arms new and old have one bolt either side threaded in to the frame with bushes or bearings.
Need more info could either be something compressive to stop collapsing as in cock on length or as above reduce flex with an M16 bolt and play. Either way that dia is going to weigh, it all adds up.

[Brass_Machine]

C-O-C if you will.

But it all depends on what it is going to be used for. It almost sounds like a spacer to fit a swingarm from one bike to another, where the bolt is going to be small on the bike receiving the swingarm.

Definitely need more info, because if it is the above, need to take in account what the bolt is made out of etc... I posed a question like this to the frame list I belong to. They have members from some of the elite in motorcycle frame building. With a little more info, I can give you the answers.

Eric

[AdeV]

No problem, one C-o-C coming up:



Because my writing is atrocious, I figured I'd better write about it too...

Basically: it's a cylinder. The 17mm bore had a bolt that passes right through it, & clamps the piece into place. At least 1 (maybe 2?) bearings ride on the outside of the main diameter. Another bearing rides on the 20mm diameter, this is held in place with a 7mm wide x 28mm dia spacer, seen to the left. The whole thing is 230mm long. The current piece, which is too short IIRC, is made of "steel" - not sure what kind. I'd planned to use either EN1 or 330 stainless, depending on the recommendations made here.

[Brass_Machine]

I am going to assume it is a spacer of some sort. One to take up the gap left between a smaller pivot bolt and a larger through hole on the swingarm. Since the swingarm is riding the bearings and not the spacer, steel should be just fine. Personally for corrosion etc... use stainless.

Hope that helps

[AdeV]

Thanks Eric - I think you're right; he did mention something about 1/4mm clearance or thereabouts...

Excellent. I'll price up the lumps of metal tomorrow... he'll get stainless if it's not too dear.

[AdeV]

Done! A bit later than anticipated, mostly due to work - there was I hoping for a quiet week, but oh no. Complete chaos...



This is, of course, the second one... the first one suffered a massive tool crash (biggest one for me yet) which destroyed a tip, damaged the tip holder, damaged the QCTP holder (fortunately, the main QCTP survived), and bent a foot of 30mm steel bar such that the runout was approximately an inch. The cause? Easy; when going from a surfacing to a facing operation, I forgot to change the apron gears, so when I engaged the drive, the carriage pushed into the work instead of across it... Seeing my error immediately, I went to disengage but accidentally pushed the lever too far, into screwcutting mode... well, at 400rpm, it didn't take more than a second for all the damage to be done. By the time I hit the e-stop, the lathe had already stalled.

Fortunately, all the damage was easily remedied, except to the work piece. I did try to carry on (after straightening the bar as best I could), but the central hole ended up off-line, hence having to make the second one. Anyway, the 2nd one looks better IMHO, and is definitely holding a tighter tolerance to dimensions, and it only took around 1/4 of the time to make... Next time, I'll make a practice piece in ali first...

I'd also like to hat-tip Bogs at this point - your suggestion of using a home-made drill extension to turn a 4" blacksmiths drill into a 8"+  deep-diving beastie was an excellent one. It worked a treat, once I'd ground the back end of the drill down a bit.

[Brass_Machine]

Very good Ade!

That's a nice looking piece. The owner owes you a drink! Pictures of what it is used for would be nice from him as well... Cause I am curious 

Eric

[Jonny]

Must have a larger lathe decent finish as well. Bet that took some drilling.
Since he didnt specify a material that must weigh a lot

Still want to know what its for.

[AdeV]

Thanks chaps

As I understand it, it works like this: There are 3 bearings on this piece; one (a roller bearing) sits in the cut-down section, it has a spacer next to it, and is trapped in place by the frame. The OD of the bearing & spacer bring the whole piece to a 28mm bar. On this bar, 2 caged bearings ride, the swing arm then rides on these bearings, and the whole lot is bolted in between the frame with one mahoosive 17mm bolt. I think the idea is the swing arm rotates around the bar (which stays stationary) as the suspension does its thing. I'm not quite sure what the small bearing does, or why its there.

Once assembled, it is apparently right down in the black depths between engine & wheel & gears and brake lines & such like, so it not that easy to see. However, I'll ask him to take some pics of it as it's assembled, so we can all figure out how it works!

Jonny, thanks - yes, my lathe is quite chunky, 6.5" centre height & approx 40" bed. It's also old & slow, so the only way I can get a finish like that is to sneak up on the final cuts at around 0.001", which is fairly tedious. I used an Aluminium-cutting insert (available from Chronos) instead of a regular carbide cutter to make the final cuts, I plan to buy a few more of them as they're really good on a range of materials, much better at finishing than Carbide alone.

The cutting was followed with about 10 mins of work with some coarse valve grinding paste, then some 600 grit wet & dry paper (wetted with cutting oil rather than water), and finally some Meguiars "NXT generation All Metal Polysh" metal polish, to give it a bit of a shine.

Material is regular EN1 mild steel.

[Pete.]

Looks good. It'd be interesting to know the exact application. On most swingarm/wheel spindles (well, all that I've seen) the bearing inner races are clamped together by the through-bolt. As standard, a swingarm would have a spacer fitted loosely in the space between the bearings and the spindle would pick up that spacer pulling the lot together. For alignment, you would fit one particular side bearing into the arm first and press it against a shoulder then press the second bearing in up to the spacer.

Since the larger bearing in your sketch does not sit against a shoulder on the shaft you made, that won't be the case here. A piece that size would fit into quite a hefty bike and I'd be wondering about what flex or movement there would be from not having the bearing races all clamped together.

[AdeV]

I now have some pictures from the bike builder. Apparently, the piece fitted nicely & is working fine (phew!)

Here's the swing arm:



My piece fits in the far right hand bit. Here it is fitted:






On the bike frame:



And the finished(ish) article:



As you can see, the bit I made has completely vanished  

Still, it's nice to know it's doing the job  

[Brass_Machine]

Nice work Ade! Glad to see it is doing it's job.

Nice looking swingarm too. Definitely not stock.

Eric

[MrFluffy]

Nice work, its a stock zrx1100 swingarm by the looks of it. The 1200 is the double tube version, but the 11 only got singles. Theyre nice on the eyes and its common to see them getting swapped in other stuff.
Call me mr swingarm spotter, Ive got a chart on my forum of all the dimensions and photos and stuff

[Brass_Machine]

Nice work, its a stock zrx1100 swingarm by the looks of it. The 1200 is the double tube version, but the 11 only got singles. Theyre nice on the eyes and its common to see them getting swapped in other stuff.
Call me mr swingarm spotter, Ive got a chart on my forum of all the dimensions and photos and stuff

ahhh that is probably what it is. So, not stock for the zephyr 

I don't know a lot about the naked bikes...

[AdeV]

MrFluffy, you're spot on, it's from a ZRX1100, the builder did mention that in his build thread. Unfortunately, it's on the Zephyr Zone website, which won't let guests view their forum, and the registration requirements are stricter than most.

He's wanting something doing to the forks next  not sure I'll be good enough for that job...

[MrFluffy]

Does he want you to adapt the zrx yokes or make new ones up?
Mostly the factory yokes have a pressed in spindle with a collar on the end to stop them pulling through. I pop the spindle out downwards in the press after a fettle to remove any keeper welds if its a steel bottom yoke. Then turn a new spindle to match the dimensions of the yoke and the original yoke spindle dimensions and press it in the yokes. Apart from the single point fine thread for the top bearing clamp nut and getting the areas where the bearings sit bob on within limit and fits its not a tricky exercise.

[AdeV]

Does he want you to adapt the zrx yokes or make new ones up?
Mostly the factory yokes have a pressed in spindle with a collar on the end to stop them pulling through. I pop the spindle out downwards in the press after a fettle to remove any keeper welds if its a steel bottom yoke. Then turn a new spindle to match the dimensions of the yoke and the original yoke spindle dimensions and press it in the yokes. Apart from the single point fine thread for the top bearing clamp nut and getting the areas where the bearings sit bob on within limit and fits its not a tricky exercise.

I'm not entirely sure yet; he said something about modifying the bearing & how there's not a lot you can hold onto... until he drops in again next week, it'll be a bit of a mystery...