SteveW
Elder Statesman
Posts: 1,459
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Post by SteveW on May 14, 2005 22:24:24 GMT
Guys,
I've not long returned from a rail based holiday in Switzerland and, armed with a rail pass, traveled the system of both standard and metre gauge track. Very shortly after leaving Brig toward Zermat on the metre gauger we contacted our first rack with a bump and off up we went.
On further examination it appears the pressure line on the rack was higher than the top rail surface which I take means the pinion is a smaller diameter than the wheel it shares an axle with. How can this be? Am I missing something?
(Hey! I just found the spell checker, it's US but neat)
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Post by greasemonkey on May 15, 2005 15:01:27 GMT
Hi Steve
Im no expert, but if the pinion and wheel are doing the same RPM then diameter surely doesnt matter? If the pinion was the same diameter as the wheel or larger you would have problems negotiating switches and crossings.
Andy
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Post by Phil Sutton on May 15, 2005 19:37:52 GMT
If it is a"pure"rack railway,ie,the loco runs by rack propulsion only,then the cylinders drive the rack pinions,and the wheels are loose on the axles.If it is driven by both rack and adhesion, then the above explanation is probably correct.
Phil
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Post by Tel on May 15, 2005 20:27:07 GMT
My thoughts exactly Andy, one revolution is going to be one revolution, regardless of diameter Hi Steve Im no expert, but if the pinion and wheel are doing the same RPM then diameter surely doesnt matter? If the pinion was the same diameter as the wheel or larger you would have problems negotiating switches and crossings. Andy |
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SteveW
Elder Statesman
Posts: 1,459
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Post by SteveW on May 15, 2005 21:22:22 GMT
Andy, (Guys,)
Good point on the need for different diameters of wheel/pinion to allow for points. These things were quite interesting to see on this railway system, a bit like my old three line Hornby OO track. I wish I'd taken the time to photograph one. The bits at the start of the rack sections to sync the pinion were quite intriguing too. There were two distinct short racks before the main rack started.
My problem is the pinion and wheel have to be independent on the axle because the peripheral speeds of the wheel rim and the effective drive point of the smaller pinion will be different for the same speed.
This would lead to separate drive/braking for normal traction and rack traction. Either way the way the thing blasts off up hill was amazing.
Anyway, thanks for the thoughts so far.
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Post by greasemonkey on May 15, 2005 22:21:40 GMT
Hi Steve
The inital rack sections you refer to are designed to give as the pinions engage. Its a bit like a ruler being twanged over the edge of a desk. The peripheral speeds are diffrent because of the diffrent diameters andtherefore circumfrence but if they are joined on the same axel they still spin at the same RPM. Get hold of some meccano or technical lego and have a play. See if you can get hold of a set of construction articles for Kopple designed by I think Ken Swan that may answer a few questions.
Andy
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Post by steamjohn248 on May 16, 2005 22:12:15 GMT
A big wheel will travel further in one rev than a small one so if they were solid on the same axle we got a problem. If you ever go to Greece on hols have a trip up the rack/adhesion railway on the south side of the gulf of Corinth that is scary!
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Post by Tel on May 17, 2005 10:36:47 GMT
By a great stroke of coincidence I recieved four x 1m lengths of rack in the mail today (an eBay bargain) - might be amusing to set up an experiment I think.
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Post by greasemonkey on May 17, 2005 19:54:48 GMT
let us know how you get on Tel
Andy
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Post by Tel on May 17, 2005 22:06:30 GMT
I surely will GM, be a few days til I get to it tho'
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Post by Tel on Jun 6, 2005 10:19:20 GMT
BUMP
Haven't forgotten this blokes, just haven't had a chance to do anything yet
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