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FF: Forks Brampton Steering Stops


ogrilp400

Well Known and Active Website User
VOC Member
G'day All,
What is it with Brampton Forks missing the steering stops on B head lugs and then the rear fork tubes banging into the tank? Am I missing some thing here? And no, there isn't a spacer under the bearings, its as far up as it can go.

Phelps.
 

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Cyborg

Well Known and Active Website User
VOC Member
On my B the FT124 steering stem sits up a little higher than yours and the rib (on the FT124) comes into contact with the steering stop. Although it does come in contact with the side of the rib, so would reduce travel more if the stem was slightly higher. Is the lower bearing outer race all the way home in the steering head? I assume the balls are the correct size. Has the lower outer race been recently replaced? If so, within reason you could tighten down the nut on the steering stem and see if the lower outer race moves up at all. It’s a normal procedure with taper rollers to torque things down to make sure everything is seated and then back off and re-torque to spec. That said, I’m a little nervous about putting too much torque on a loose ball setup. Best to make sure it has the correct “ring” to it when initially installed.
 

ogrilp400

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VOC Member
I have done four of these in recent years and they are all the same. I remember the first one I did and I thought something must be amiss, surely the rib should contact the stops on the head lug. Pulled it all apart but could not find anything out of place.
 

Cyborg

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VOC Member
Well that is weird. Although from looking at mine, it doesn’t seem very well thought out. Yes it would make a lot more sense if the rib contacted the stop directly. With mine, “it works” but wouldn’t take much wear to allow more travel.... given it contacts the side of the rib so hits the stop at an angle. I have another FT 124, so will have a look at it later today and see if there is anything noteworthy. I can’t really compare it to the one that “works” because it’s in the bike. Unfortunately I don’t have another B headstock to play with.
 

oexing

Well Known and Active Website User
VOC Member
Sorry, no, nothing wrong with bearings, just the stops on the head lug are plainly too short for a nice contact. I found this when designing a hydraulic steering damper for the Brampton and simulated the set with pastic bushes in head lug with same dimensions like the ball bearings. So I will extend the stops with weld by 1/4 " and do flats there for some rubber glued to them. A hard BAM!-stop would hurt my soul - unacceptable.

Vic
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Cyborg

Well Known and Active Website User
VOC Member
No need to apologize. You are correct. I had a look at my other FT124. Slid it into a C headstock which is different, but the location of the stops are possibly the same. No logical way to change bearing location or remove any metal, so only option is as you say to add metal.
This photo is without the inner race on the FT124 and obviously no bearings. In as far as it can go and still just catches the edge of the rib. The rib on the assembled B is farther down and contacts more on the side of the rib. Probably wouldn’t offer much protection for the tank if the front end was walloped.... or if you could induce a tank slapper.
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ogrilp400

Well Known and Active Website User
VOC Member
Surely this was not the case back in 1947-48. The forks would have been bashing into the tank.
 

Cyborg

Well Known and Active Website User
VOC Member
Beats me... with mine... in order to get that rib to squarely contact the stops without adding some silicon (or aluminum bronze would be better) bronze to build up either the stops or the rib... one would have to machine the bottom bearing bore deeper and remove material from the bottom of the headstock so the FT 124 would clear. Doing that might necessitate some sort of modification at the top with the stem sitting higher. If you had 4 the same and mine is just “OK”, then I guess it’s the luck of the draw with whatever tolerances they built to. Did you search the forum to see if it’s come up before?
 
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vibrac

Well Known and Active Website User
VOC Member
When I raced with Brampton's I had a vee of alloy attached to the stop protrusion but then I was reducing the movement for racing I would look at my Comet but it's on the bench in a front wheel clamp at the moment
 

oexing

Well Known and Active Website User
VOC Member
Adding weld to the rib would produce a banana shaped Brampton part - not recommended. And setting the lower bearing seat higher is a very awkward operation, you have to keep alignment and parallel seats of upper and lower bearing absolutely spot-on - not easy to do.
So really you´d better add some weld to the stops on the head lug, no risk of deformation there, you can use simple arc welding with standard rods. The head lug is most likely low carbon steel casting so no problem with welding added to extend the stops. A few wet rags around and you could do it on the bike. The stops were effective on most Brampton bikes I guess, but just and no great contact face there so some mod is a good idea.

Vic
 

Cyborg

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VOC Member
Just for the record, I wasn’t suggesting the machining and it would be a very poor alternative to adding weld.... and yes adding the weld to the steering stops would be preferable. Although...not sure why adding it to the rib couldn’t be done without warpage.
 

oexing

Well Known and Active Website User
VOC Member
Well , yes , a short length of weld on the rib would be OK possibly. But would not want to bet on no shrinkage in the weld that puts bushes out of alignment in the Brampton part. Welding with no shrinkage is an impossible task anywhere so you have to live with it somehow. Anyway, no big advantage to have the rib welded instead on the stops I´d say, so better do the stops.

Vic
 

vin998

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VOC Member
VOC Forum Moderator
Be careful when welding the stops as the earlier type 2 headlugs were made from mallable cast iron. The later type 4 headlug & series D is the type which drops inside the slotted headbracket were steel.

The photo in the initial post by ogrilp400 is a type 2.

Simon
 

Cyborg

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VOC Member
I’m guessing either way some silicon bronze stitched on there carefully with a TIG would be ok. No need to melt the base metal (if you’re good at it) which means it would be wise for me to take over to the dude who works in aircraft maintenance rather than practice on expensive parts. Currently I’m only certified for yard art.
 

erik

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VOC Member
If someone doesn`t want to weld an other solution is to use the pin of the steering damper on ufm an alter the screw to an big shim which stops the steering.Erik
 

oexing

Well Known and Active Website User
VOC Member
Actions speak louder than words : I did some welding on the head lug stops for the Brampton last night, had to do it anyway some day. A grinder test on the head lug produced not so sparkly sparks so my guess it is a low carbon steel casting, no cast iron . I would have been deeply shocked if I found otherwise for a stressed frame member on a bike. So my thinking is some welding for extending the stops a bit is non-critical, hammer tests allright, no brittleness with low carbon steel. Welding on the stops is not critical having no effect to the rest of the head lug dimensions.

Vic
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vin998

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VOC Forum Moderator
In Know Thy Beast pg 21 and it says the early type 1 head lug of which yours is Vic is a forging but doesn't mention the material. Type 2, of which the initial post by ogrilp400 shows, is a malleable iron casting and last type which is FT1/4 even though the book calls it the third type is a cast steel item of solid H section.

Having seen a FT1/2 type after an accident it is definately mallable cast iron as the headlug split open and the grain structure etc was visible.

So it all depends what type of headlug you have.
 

Albervin

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VOC Member
I have been reading this with interest as I ride an early Series B Rapide. There is no doubt the clearance on full lock is very close and the fitting of the valve lifter needs care. However, I have ridden many thousands of Km and not experienced a problem. The tank is well clear of any impact. The stops hit below the webs. So were the webs supposed to be the stops or just reinforcing? My lower yoke was the only part damaged beyond repair besides the snapped tubes in the great garage catastrophe last year. All other links were just fine. I will be interested to know what steering lock is available with Vic's adjustment.
 

Cyborg

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VOC Member
I don’t know what the factory’s intent was, but it would definitely make more sense if the rib squarely contacted the stop. The fact that it contacts the stops at an angle means that any slight variation in the location of the FT124 (up or down) would allow a greater change in travel. Given the machining tolerances of the day... that could mean you and I were lucky and Master Phelps not so much. Is there something else coming into play that caused him to have a string of bad luck? At the end of the day, it seems (at least in my photo above) that the FT124 hits the headstock before the rib can get square against the stops. Other than rather random tolerances etc the only other variable (based on info provided in posts 1,3) would be the lower bearing. As in were the bearings replaced? What were the dimensions of the replacement bearings versus the originals. Not just the width of the outer, but the total width including outer, balls, and inner. Perhaps the business part of the race wasn’t ground as deep? Again.. given the rib contacting at an angle, it would not take much to allow more travel.

Does the spares co. have any drawings that would show the dimensions of an assembled bearing?
 

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