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Issue lacing 1949 m21 front wheel #750678
09/27/18 8:27 am
09/27/18 8:27 am
Joined: Dec 2014
Posts: 159
Perth, Western Australia
H
Howley Offline OP
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Howley  Offline OP
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Joined: Dec 2014
Posts: 159
Perth, Western Australia
Hi all,

I'm having issues lacing my 1949 m21 front wheel. I've got the type 3 front (7" half width) as per https://www.draganfly.co.uk/index.p...category/915-3-front-wheel-7-a-b-m-group

My spokes are 7 1/2 and 8 3/4 long as listed elsewhere on Draganfly website, and I've got it laced as shown below:

https://drive.google.com/file/d/1s3PEJIePSk9RZsSSyi2HG-M5U5mZbKIC/view?usp=drivesdk

The offset is nominally correct, set by the blocks.

My problem is the short spokes are all done up nearly to max, they seem a little long (1/8" or so), and the long spokes are way too long (1/2") as per the picture below:

https://drive.google.com/file/d/1e6uIk9HUSRCAJ-c7XYjXWNUWRHVTeTMY/view?usp=drivesdk

Is there something wrong with my lacing, or are the spoke lengths incorrect?

Help!

Luke

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Re: Issue lacing 1949 m21 front wheel [Re: Howley] #750692
09/27/18 11:00 am
09/27/18 11:00 am
Joined: Dec 2014
Posts: 159
Perth, Western Australia
H
Howley Offline OP
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Howley  Offline OP
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Joined: Dec 2014
Posts: 159
Perth, Western Australia
I pulled it apart and started from the long spokes, and I got them to work out. The problem is that I have no idea of how what I've done now differs from what I did initially. This is my second go at wheel building, so I think there may be a particular intricacy that I'm not aware of. Can anyone enlighten me?

Re: Issue lacing 1949 m21 front wheel [Re: Howley] #750695
09/27/18 11:33 am
09/27/18 11:33 am
Joined: Dec 2004
Posts: 9,549
Scotland
kommando Offline
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kommando  Offline
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Scotland
Look up Gunners thread on the 8" hub, same spoke pattern so check that thread as it has the info, if I could find my 7" wheel I will post photos.

Re: Issue lacing 1949 m21 front wheel [Re: Howley] #750809
09/28/18 9:09 am
09/28/18 9:09 am
Joined: May 2009
Posts: 98
Australia
M
MattL Offline
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MattL  Offline
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Joined: May 2009
Posts: 98
Australia
G'day Luke,

The lace pattern in the first photo looks correct with a quick check of my front wheel, it doesn't take much error in offset to throw the spoke length out. You might have noticed that loosening one side 1 turn and tightening the other side 1 turn can alter the rim offset by 3 or 4 mm.

Re: Issue lacing 1949 m21 front wheel [Re: Howley] #750837
09/28/18 5:23 pm
09/28/18 5:23 pm
Joined: Dec 2004
Posts: 9,549
Scotland
kommando Offline
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kommando  Offline
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Joined: Dec 2004
Posts: 9,549
Scotland
Found my 7" wheel and have taken pics, will post them tomorrow but you have definitely got the long spokes in the wrong holes and they need to be further apart on the center.

Re: Issue lacing 1949 m21 front wheel [Re: Howley] #750900
09/29/18 8:45 am
09/29/18 8:45 am
Joined: Dec 2004
Posts: 9,549
Scotland
kommando Offline
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kommando  Offline
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Joined: Dec 2004
Posts: 9,549
Scotland
Photos marked with spoke holes on hub to be used.

[Linked Image]


[Linked Image]

Re: Issue lacing 1949 m21 front wheel [Re: Howley] #750907
09/29/18 9:34 am
09/29/18 9:34 am
Joined: Dec 2014
Posts: 159
Perth, Western Australia
H
Howley Offline OP
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Howley  Offline OP
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Joined: Dec 2014
Posts: 159
Perth, Western Australia
Thanks Kommando.

I've got the pattern right now and things look better.
I've got a question about both ends. What I've got makes sense but I just need to clarify that what I've got is normal.

FRONT
All long spokes are the same length. All short spokes are the same length. All the spokes coming from the inside of the hub (generally) finish about 1mm outside the nipple, and all spokes coming from the inside finish about 1mm inside the nipple. With the rim tape on a lump can be felt but it won't puncture anything. Is this normal?

REAR
All spokes are the same length. When complete, the centre of the hub (exclude brake drum) is not on the frame centreline, meaning the rim is offset from the hub towards the drive side. As a result of these two points, the drive side spokes all finish around the end of the nipple, and all timing side spokes finish with the thread just inside the hub side of the nipple. Is this normal? If I was to set them equal the offset would be out by an inch.

Both wheels have been trued, dished and tensioned.

To me it seems like the front should have 4 spoke lengths and the rear two.

Thoughts?

Re: Issue lacing 1949 m21 front wheel [Re: Howley] #750916
09/29/18 11:06 am
09/29/18 11:06 am
Joined: Dec 2004
Posts: 9,549
Scotland
kommando Offline
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kommando  Offline
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Joined: Dec 2004
Posts: 9,549
Scotland
The offsets are derived from the prototype which had the front wheel central to the forks, I use the front offset as a guide, true and tension but then mount the wheel and center the rim in the forks. Do not have a rear for a m21 to make a comment.

Re: Issue lacing 1949 m21 front wheel [Re: Howley] #750951
09/29/18 7:01 pm
09/29/18 7:01 pm
Joined: Aug 2015
Posts: 1,267
Bolton Lancs UK
A
Andy Higham Offline
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Andy Higham  Offline
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Joined: Aug 2015
Posts: 1,267
Bolton Lancs UK
If the spokes protrude past the nipple they WILL puncture the tube


BSA B31 500cc "Stargazer"
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Jawa 500cc "Llareggub"
2003 Aprilia RSV Mille "Lo Stregone"
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Re: Issue lacing 1949 m21 front wheel [Re: Howley] #750966
09/29/18 10:33 pm
09/29/18 10:33 pm
Joined: Dec 2014
Posts: 159
Perth, Western Australia
H
Howley Offline OP
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Howley  Offline OP
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H

Joined: Dec 2014
Posts: 159
Perth, Western Australia
Should I be removing those spokes and shortening them? Is there a way to do it without removal apart from hitting them with a grinder?

Re: Issue lacing 1949 m21 front wheel [Re: Howley] #750968
09/29/18 11:23 pm
09/29/18 11:23 pm
Joined: Mar 2005
Posts: 10,221
Boston, Massachusetts
J
John Healy Online content
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Joined: Mar 2005
Posts: 10,221
Boston, Massachusetts
This matches later BSA front brake hubs where they used a cross 4 pattern.


Re: Issue lacing 1949 m21 front wheel [Re: Howley] #750982
09/30/18 6:15 am
09/30/18 6:15 am
Joined: Dec 2004
Posts: 9,549
Scotland
kommando Offline
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kommando  Offline
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Joined: Dec 2004
Posts: 9,549
Scotland
Should I be removing those spokes and shortening them?

Shorten yes

Is there a way to do it without removal apart from hitting them with a grinder?yes

Use a grinder

Re: Issue lacing 1949 m21 front wheel [Re: Howley] #750987
09/30/18 8:59 am
09/30/18 8:59 am
Joined: Dec 2014
Posts: 159
Perth, Western Australia
H
Howley Offline OP
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Howley  Offline OP
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Joined: Dec 2014
Posts: 159
Perth, Western Australia
Deal!


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