steering neck angles

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Re: steering neck angles

Postby JerrryR » Sat Jan 12, 2019 2:09 pm

I agree with XLH59 that his frame has a 57R neck based on the XL style top motor mount, no front downtube "doublers" and the reinforced neck design.
My question is what year and models used the 57R neck casting? The photo of the 57XLR-TT I believe is using the -52 neck casting. Should it be the -57R casting or the -52 casting? Were there only two racing frame part numbers, the 52R and the 58R I've seen mentioned in this thread? Did the 57R neck first show up with the 58R frame mentioned? If the 57XLR pictured is using the -52 neck because it is an early mock-up I understand. If you look closely at the photo of the mock-up 52K you can see that its early K frame is lacking the welded on strut supports.

First K Pohlman Photo no Fender Strut.JPG
First K Pohlman Photo no Fender Strut.JPG (24.99 KiB) Viewed 10642 times


I believe the 52K, 52KR, KRTT, KRM and 57XLR-TT are all displaying the -52 neck casting. I would guess that the 56KRTT photo shows a -52A neck casting. An easy way to ID the -52 casting is its lack of neck reinforcing. All subsequent neck castings I am aware of are reinforced like the -52A shown.

52 Neck Non-Reinforced Area.JPG
52 Neck Non-Reinforced Area.JPG (33.11 KiB) Viewed 10642 times


52A Neck Casting Reinforced Area.JPG
52A Neck Casting Reinforced Area.JPG (32.2 KiB) Viewed 10642 times


I'm thinking the 56KRM shown is using the -52A casting based on no doublers and being reinforced.

I admittedly know little about racing frames and bikes so any corrections for my assumptions or additional racing frame information would be much appreciated.
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Re: steering neck angles

Postby xlh59 » Sat Jan 12, 2019 3:15 pm

as the frame is in my hands, I thought I can take measurements or pictures (whatever is needed) -- the frame has no alterations beside the nasty "smoothening". The neck has not been welded which is visible from inside -- therefore the steering angle is 25° for the 57R neck casting. The question is rather on what bikes this frame has been used ...
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Re: steering neck angles

Postby hugoct » Sat Jan 12, 2019 3:31 pm

The first XLRTT was a 1958 model
Both the 52R (heavy) and 58R (light) frames used the 57R casting from 1958 on.
The 1952 version of the 52R frame uses the 52 K steering head.
The steering head changes to the 53R for 1953
The steering head gets pulled in by 2 degrees for 1954 and is a 53RA steering head which appears to be the welded steering head with 25 degree rake.
That steering head gets repalced with the 57R casting in 57 but remains a 53RA part number and is used on both the 52R and 58R frame.
The Sportster XLRTT does not get the 58R (light) frame.
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Re: steering neck angles

Postby xlh59 » Sat Jan 12, 2019 4:21 pm

That sounds reasonable. Is there any tangible information in the "light" and "heavy" frame? Wall thickness or total weight? Would any KR after 57 use a frame with stamped steel top motor mount?
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Re: steering neck angles

Postby hugoct » Sat Jan 12, 2019 5:06 pm

The 52R (heavy) frame and 58R (light) frames for any given moment are identical dimensionaly and visualy.
To verify what you have a scale would be the alternative to trying to determine wall thickness.
Between 1952 and 1970 the 52R was changed 22 times and between 1958 and 1970 the 58R frame was changed 10 times.
The 52R and 58R frames were used on KRs.
The 52R frame was the only frame availble on the XLRTT.
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Re: steering neck angles

Postby No side stand » Sat Jan 12, 2019 6:23 pm

Hi hugoct.
Thanks for sharing your information on race frames. Is your information garnered from personal experience, or are you relating information that is from factory printed information?

On the issue of thin, and thick wall thickness, if the backbone is drilled for the 2 ¼ gallon gas tank, the back bone wall thickness can be checked through the hole for the rear tank mount.
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Re: steering neck angles

Postby hugoct » Sat Jan 12, 2019 6:35 pm

I'm going off the component list and the change list on the blueprints.
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Re: steering neck angles

Postby JerrryR » Sat Jan 12, 2019 6:52 pm

I have images of two racing frames that I am curious as to what their designation and use would be. I'll show the images in several post to get them all in.

57R Frame 1.JPG
57R Frame 1.JPG (18.07 KiB) Viewed 10622 times


57R Frame 2.JPG
57R Frame 2.JPG (38.78 KiB) Viewed 10622 times


57R Frame 3.JPG
57R Frame 3.JPG (25.71 KiB) Viewed 10622 times
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Re: steering neck angles

Postby JerrryR » Sat Jan 12, 2019 6:54 pm

more 57R

57R Frame 3.JPG
57R Frame 3.JPG (25.71 KiB) Viewed 10622 times


57R Frame 4.JPG
57R Frame 4.JPG (33.4 KiB) Viewed 10622 times


57R Frame 5.JPG
57R Frame 5.JPG (38.67 KiB) Viewed 10622 times
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Re: steering neck angles

Postby mikeslemmon » Sat Jan 12, 2019 7:21 pm

I'm thinking that so much one off stuff came from the racing department that without the frames history we'll never know. didn't the lowboy and highboy frames come along in about '67 or '68? .Rick bray had one in his shop in '67 .
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