If I buy a jig for code 83, can I also do code 70 in it as well? I know that code 100 is totally different in the base measurments, but thought that 70 and 83 were very close in the base widths.
Kurt
P.S. this is a test of signatures.
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| Track usage in assy fixtures. http://fast-tracks.net/forums/viewtopic.php?f=5&t=864 |
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| Author: | Kurt Konrath [ Wed May 28, 2008 10:42 am ] |
| Post subject: | Track usage in assy fixtures. |
If I buy a jig for code 83, can I also do code 70 in it as well? I know that code 100 is totally different in the base measurments, but thought that 70 and 83 were very close in the base widths. Kurt P.S. this is a test of signatures. |
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| Author: | Tim Warris [ Wed May 28, 2008 11:41 am ] |
| Post subject: | Re: Track usage in assy fixtures. |
[quote="Kurt Konrath"]If I buy a jig for code 83, can I also do code 70 in it as well? I know that code 100 is totally different in the base measurments, but thought that 70 and 83 were very close in the base widths. Hi Kurt, Yes, you can use code 70 and code 83 in the same fixture as the critical dimensions are very close and can reliably be interchanged. |
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| Author: | jdm_com_au [ Thu May 29, 2008 12:52 am ] |
| Post subject: | Re: Track usage in assy fixtures. |
The base width will determine whether the rail will physically fit into the jig ( or how loose the fitment will be ) and the head width can potentially alter the track gauge if the difference is too great. Using a rail with a larger head width than the design called for would be the worse of two evils, as that could potentially reduce the gauge to the extent that de-railments could occur, as the HO jigs are generaly set at the minimum recommended gauge. The same situation could occur if you use rail other then ME, as other brands generally have slightly different dimensions. I think one of my first posts delved into this problem. |
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| Author: | Tim Warris [ Fri May 30, 2008 2:02 pm ] |
| Post subject: | Re: Track usage in assy fixtures. |
| Author: | jdm_com_au [ Sun Jun 01, 2008 12:57 am ] |
| Post subject: | Re: Track usage in assy fixtures. |
| Author: | Tim Warris [ Sun Jun 01, 2008 9:59 am ] |
| Post subject: | Re: Track usage in assy fixtures. |
| Author: | emccamey [ Sun Jun 01, 2008 4:19 pm ] |
| Post subject: | Re: Track usage in assy fixtures. |
First don't mix Proto:87 with 'regular' HO - the 'regular' is which the FastTracks fixtures are designed for (NMRA S3.2 standards). Custom fixtures were once avialable - but Tim has not regularly support these when his manufacturing backlog is stacked up. There is no realistic interchange comparison between Proto:87 and the standard specifications. Beyond gage, there's big differences in check gage, flangeways, and several other aspects of the trackwork. Further, regular RP-25 code 110 or code 88 wheels will not operate with Proto:87 trackwork. P.S.: Proto:87 code 64 wheels do not operate reliably on 'regular' HO trackwork either. The regular HO minimum is 16,5mm and an allowed gage widening maximum (on running track and non-guarded curves) at 17,1mm. There is a proposed update to the S3.2 standards open for comment that tightens the gage widening allowance in guarded trackwork - but this is not in the standards at present. The reality is that the guarded trackwork was never intended to have the running track maximums allowable - but the standards did not and at present do not clairfy that point, the proposal does correct that. Certain configurations of special trackwork will operate much better with dead tight gage, but allowances have to be made in tolerances for manufacturing and materials assembly and production. |
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| Author: | jdm_com_au [ Mon Jun 02, 2008 2:58 am ] |
| Post subject: | Re: Track usage in assy fixtures. |
Obviously I did mis-understand something.  So if the standard gauge HO fixtures are set at 16.76mm (0.660"), that's all I need to know about that. Is the HOn30 and N scale fixtures set at 9.1mm (0.360"?) gauge? I'd just hate to make another silly assumption. Especialy when those who know the correct answers are more than willing to give out the correct info.Ed, I simply assumed that Proto:87 was the same as HO. Obviously not. I'd rather ask questions now and find out I'm wrong, rather than spend money making a dual gauge turntable jig and finding out my mistake the hard ( and expensive) way. Thanks. |
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| Author: | emccamey [ Mon Jun 02, 2008 10:30 am ] |
| Post subject: | Re: Track usage in assy fixtures. |
The track gage has a nominal minimum. In straight track and broadly curved track, the minimum is far better in reliability and operations. So for HO, setting the track gage at 16,5mm is the proper course of action. Allowable gage widening is to accommodate the binding of long wheel bases in compressed curvature. Historically, HO has used very sharp curvature, 18" is the typical, but even 16" or slightly less has been used extensively. Under that kind of extreme compression, steam drivered (and longer trucks of 3 axle motive power) will bind at the nominal minimum track gage, so allowances for gage widening is provided. Wheel sets are specified at wheel check gage values with a defined wheel flange. The wheel sets have a wheel gage (facing flange to facing flange) that has a fair tolerance of freedom for the minimum track gage, but then when chassis mounted and in a curve, the axles no longer run perpendicular to the railheads on the outside ends. Guarded trackwork (turnouts, crossings, special work) has to provide guardrails to protect the frog gaps as well as have flangeways that allow the defined flanges to negotiate the route. At the same time the wheel tread area needs to ride across the railhead gap and should maintain contact over the wing rails. Getting all the relationships correct means that you have well defined wheel profiles with consistent flanges, wheels set on axles within a narrow range of fitting tolerance, and trackwork that covers all the relationships. Read through and study the NMRA RP 10, the RP 2. 'Regular' HO standards (S3.2 and S4.2) track and wheel relationships provide somewhat overly generous tolerances to account for those historical extreme compressed curves. Absolute best reliability for operations, is to have quality wheelsets, far more generous curves for the equipment in use (see S6 and RP11), and much tighter allowances if interrelationships. HO track gage is 16,5mm. It has gage widening allowance to work with your chosen equipment and consequences of layout space. You can stretch the limits, but then operational reliability begins to suffer dramatically. FastTracks has chosen a set of allowances within the nominal ranges for the compromise of construction and running reliability. There are FOUR separate sets of standards for scale and gage combination (over 140 combinations world wide) - though not all combinations of scale and gage have all four instances of standards. 1) Proto standards is dead on scaling and very very tight tolerances. This will NOT interchange with other standards. 2) FINE standards are higher fidelity to scaling and appearance, but require modifications to commercial equipment and tighter allowances. With some careful choices and compromises, one can interchange the 'scale' and 'fine' equipment. 3) Scale standards - the 'traditional regular' scale dimensions and the most widely installed base. One can adjust the allowable ranges of specifications to meet better reliability with specific choices of equipment and curvature allowance. 4) Deep flange or High Rail standards which are based on the historic freedoms of principally the toy train sets. However there are several high fidelity commercial offerings using deeper flanges to compromise for extreme curvature compression - so this is not intended to be a derogatory category. I would be remiss if I did not also point out there are several 'standards' bodies that specify the dimensions in each category. Principally, the NMRA for US based equipment and MOROP with their NEM standards for European equipment. There are dozens of specialty scale and gage "societies" that have their own unique and specific dimensional standards as well. Equipment from one class or set of standards, even in the same modeling scale, MAY not operate reliably and interchange correctly without modifications and adjustments. As a final note on the topic thread. With FastTracks fixtures specified for Micro Engineering code 70 rail, accurate dimensions can be constructed using ME code 70, ME code 83, LaVancil code 81, older Railcraft code 82, C&L code 75, and Peco code 75 rails. All these rails have tolerances of rail base and railhead width to accurately produce results with the one fixture sizing. |
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