Fork Cups Won't Seat & Upper Bearing Seat (arm) Discovery !

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VintageTwin
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Fork Cups Won't Seat & Upper Bearing Seat (arm) Discovery !

#1

Post by VintageTwin » Mon Dec 08, 2008 12:29 am

There's still at that 0.020" gap top and bottom after I pressed in a set of '60-up cups. The '60 cups have about 3/4 of a stem. The stem/cup transition is a radius, not 90-degrees. There is a relief machined in to the i.d. of the top and bottom headstock bores for that radius.
The Mark Blankenship '49-59 cad. plated replicas are made with a 0.100" shorter stem (on purpose), to compensate for some of V-Twin's presumed or otherwise job-experienced bore depths. Since Marks cups seat with the same 0.020" gap on both bores, then stem length is not the problem. V-Twins are longer.
Could V-Twin's neck bore bottom's have a taper because of lath-walk once the drill bit is deep inside headstock :?: "Walking" is a factor that could (if not prevented) happen with I.D. boring on transmission MDG during main drive gear conversions).

The Stett-Press works effortlessly. His idea. http://stettsironhorseranch.com/" onclick="window.open(this.href);return false; helping to move the Pan scene along.
Ryder, in Houston, turned the bushings from 1/2" aluminum. Make yours 1" thick and and you'll stay well-above the cup rim.
frkcup98223fn6.jpg
These are '60 cups going in as test dummies.
Talked to Mark about the 0.020" continuing problem. He said he's had one V-Twin frame and used his '49-59 cups and he had no problem, but after listening to the details, he said it sounded like a tapered bore at both ends.
I can't feature both cups (from different manufacturers) being wider at the top near the radius.
frkcup99224ks9.jpg
That's a 0.020" blade. It's actually more of 0.021" gap. All the way around. Top cup.

Bottom cup. Same 0.020 +", gap.
frkcup102227nu1.jpg
Gaps at top and bottom. Nowhere near beginning to seat the radius transition of the cups.

The good thing: No matter how the pics look, the cups are not sitting cocked in the bore. And, the gap is even all the way around, so the plane surfaces of the necks are flat. That's good.

The reason for the cups not seating seems to be, that even with the shortest stem cups (Marks at 5/8" long) installed, and with the neck bores being a full 15/16" deep; then at some certain depth in the bores (maybe at about 1/2" deep into the bores), the bore starts to taper. If so, then maybe this taper was caused by the bit walking out of round :?:
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Last edited by Anonymous on Tue Dec 16, 2008 7:01 pm, edited 3 times in total.



mbskeam
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Re: Fork Cups Don't Seat

#2

Post by mbskeam » Mon Dec 08, 2008 4:08 am

remove about 1/16 in length from the cups, or as I suspect the radius on the cups to frame do not match up.
pop out the cups, and take a die grinder and make a bigger flat cut into the frame neck, not a radius, but a 3/32 wide flat at about 45deg....
I bet they will seat then, if that dont work,ya got a brass hammer...this would be a last resort.

mbskeam

VT

Re: Fork Cups Don't Seat

#3

Post by VT » Mon Dec 08, 2008 5:03 am

remove about 1/16 in length from the cups
I was thinking yesterday that I might have to do that, but now that I've found out that even longer V-Twin stem cups don't seat that last 0.020" either. Which means, that Marks' shorter stem (a little over 5/8" in length) get's even shorter.
So, okay, I either have to grind off the end of Marks 5/8" long stem to what?, like 1/2 inch stem length (goodbye cad plating on the end)..... or die grind inside the bores, starting at a position of 5/8th down inside the bore, and reaming upwards, a distance of about 1/2"?
Ending up with only a little more than a 1/2" of stem length is something I'd have to think about.... versus reaming, which is also something I need to think about. Thanks for the suggestion.
I emailed Don @ Corbin for an expert opinion. Might hear back.

mbskeam
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Re: Fork Cups Don't Seat

#4

Post by mbskeam » Tue Dec 09, 2008 12:44 am

no , you dont need to ream or bore any thing, just make the frames neck chamfer bigger, this will let the cups radius seat into the frame all the way....

mbskeam

VT

Re: Fork Cups Don't Seat

#5

Post by VT » Tue Dec 09, 2008 12:49 am

I'll post a pic of the neck chamfers as they shipped from V-Twin. Then you can explain what needs to be done from what you see.
frkcup104229ap0.jpg
It's the same chamfer on the neck bottom bore. The line at the bottom of the bore is the machined stop at 15/16" deep. The faint scratch line(s) about 1/8" and 3/16" above that machined line is where the V-Twin cup and Blankenship cups stop (in that order).

Hurt's my eyes, but that's the bevel depth. I'll take another pic in better light.
frkcup102227nu1.jpg
Gaps at top and bottom. Nowhere near beginning to seat the radius transition of the cups.
But what you're saying is, that in actuality, the beginning of the radius is what's stopping the cup's downward travel :?: I guess I can see that.....yeah...I'm thinking about it. Man, that's going to be some deep chamfer. Wonder how I'll control the even bevel, along with making it deeper and not make it sloppy?


Does anyone have an OE frame neck to compare the depth and/or degree of cut with the chamfers? I'd think that if the OE frame has a sharper angle to the chamfer, then the width of the (bevel) margin would be wider than mine.

I'm beginning to realize that the radius is the reason (consistent perimeter gap, apparent smooth existing bore with no chatter marks or bore bit drift) for the cups not seating. I'm trying to think of a uniform way of increasing the chamfer.
I suppose, using a barrel stone on a Foredom (Dremel), and just going around the perimeter of the neck bores will do the job. Just staring at it doesn't seem to make anything happen.
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mbskeam
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Re: Fork Cups Don't Seat

#6

Post by mbskeam » Wed Dec 10, 2008 1:05 am

if ya have a sharp bit on a die grinder you should be able to keep it pretty even....
go out a bit (1/16) and down some more from the angle cut that is in the frame already......
or you can measure the cups and see where the radius starts and ends, and see what is in the frame
it don't have to be a work of art, I wont tell...promise....
CNC hand....LOL


mbskeam

VT

Re: Fork Cups Don't Seat

#7

Post by VT » Wed Dec 10, 2008 2:27 am

(sucks up all the courage he can muster)...." I can do that :!: "
CNC hand
I'll try to live up to the same standard!

Pics will follow of the bevel mods and final cup seating. I'm stuffing paper towels in the head stock (below the 15/16 bore). Whether to grease the paper towel-wads to collect metal shavings, or keep the paper towels dry and shop-vac the shavings as I go is still undecided. I may use a (fluted) carbide burr (McMaster-Carr.com) or that barrel (cylinder) stone and do what? spin-off a bunch of grit in there too? Think not.

ImageImage-'67 Apache

V-Twin has it's own frame division now. I wonder how the current stock of V-Twin frames hang parts ?

PanPal
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Re: Fork Cups Don't Seat

#8

Post by PanPal » Wed Dec 10, 2008 4:37 pm

You know the big countersink bit they use on the inside when threading pipe in plumbing applications. This might also work.

VT

Re: Fork Cups Don't Seat

#9

Post by VT » Wed Dec 10, 2008 5:18 pm

That tapered cone shaped fluted copper or black steel pipe pipe (i.d.) reamer? Yea, maybe. I'll call Indiana Pipe & Supply and see what they have for 1-1/2 reamers. It might be a hand-reamer, not meant for chucking into a drill bit. Ridgid Tool® probably makes one. Thanks for the tip.
Looks like # 2 (34945). Reams 1/8" - 2". I'll call 'em up. but will probably resort to the Foredom fluted-burr.
http://www.ridgid.com/Tools/Pipe-Reamers2/EN/index.htm
I thought you may have had a power reamer already being in the trade
No. There are three plumbing trades: New, Repair, and Re-Model. The #2 reamer is for new construction (IAMPO ream code and Unions). Residential repair and Re-model plumbers generally wouldn't use that tool. It's all copper and ABS (black plastic) waste and vent piping out west.
Something in the V-Twin facts book would prevent using the reamer too. It reads, in part, about (steel) frame forgings:
"...the steel is first fired as a red hot ingot, next huge hammers compact and orient the grain structure.....subsequent hits....machined...(I presume, that's when the necks are bored).....and heat treated, which results in increased strength and resistance to wear."
Probably pretty hard stuff to whittle. I'll find out. Thanks for covering all the possibilities.
Last edited by VT on Thu Dec 11, 2008 3:30 pm, edited 5 times in total.

PanPal
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Re: Fork Cups Don't Seat

#10

Post by PanPal » Wed Dec 10, 2008 6:58 pm

Yea this may be more expensive also. The taper looks too extreme. It would be best using a 45 degree. I thought you may have had a power reamer already being in the trade.

steve_wood
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Re: Fork Cups Don't Seat

#11

Post by steve_wood » Wed Dec 10, 2008 9:15 pm

This may be a dumb question, but have you mic'd the stem portion of the cups? Could it be that they are actually .001 or .002 thicker just before the radius transition? If they are, perhaps that's what makes them stop seating?

And that raises another question: When you're pressing them into place, do you encounter a sudden and very significant resistance or does the resistance just increase gradually to a point where you're not comfortable turning any more?

steve

VT

Re: Fork Cups Don't Seat

#12

Post by VT » Wed Dec 10, 2008 10:05 pm

1. The measurements are the same.
2. The cups abruptly stop.
I was in denial for 1-1/2 days about the radius. John White @ tedds told me "trust me, there's a radius at that cup transition...."
I kept saying "no, it's 90 degrees..." (dyslexic to the max.), I was dummer then than now. Now mbskeam has said the same fact later down the road. The necks need to be countersunk more. I'll get to it soon.

steve_wood
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Re: Fork Cups Don't Seat

#13

Post by steve_wood » Wed Dec 10, 2008 11:51 pm

Strange. Maybe it's hard to tell from the pictures, but it looks like the bevel in the fork tube is significantly bigger than the radius on the cup.

Can you push a .001 (or .0015) feeler gauge into the gap and then down into the bevel?

VT

Re: Fork Cups Don't Seat

#14

Post by VT » Thu Dec 11, 2008 3:38 am

No the blade won't bend into the recess. It's a straight on measurement only. 0.021". The neck bevel isn't as great an angle as it might seem. I can't explain why the cup stops pressing immediately, but I know why now. I know it's because the beginning of the radius needs an immediate relief to sink into. It can't "creep up" on a relief. It needs it in advance.
You'd (I'd) think that since the gap starts before the radius edge is even making contact with the relief, that it would press further. But mbskeam's right.
I asked Stett today for an opinion. He listened. He said the same, to use a die grinder and make it a 1/16" wider and deeper (matching the existing bevel angle if possible).
Last edited by VT on Thu Dec 11, 2008 4:24 am, edited 1 time in total.

Panacea
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Re: Fork Cups Don't Seat

#15

Post by Panacea » Thu Dec 11, 2008 4:21 am

Panpal, are you thinking sprinkler pipe threader? The reamer would be stationary as the pipe is spun by the chuck, no help really in this application, unless the reamer could be removed from the machine and chucked up in a 1/2" drill, that might work....Mike

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