List,

Word of the recent discussion of near scale size couplers and draft gear boxes finally prompted me to join this forum. I spent some time last night reading the entire thread, until it was way too late to compose a reply. I'll try to make comment on all the points raised in this one message.

Material:
Both the Accumate PROTO:HO couplers and boxes are made from acetal co-polymer engineering resin; either Celcon or its equivelant. This material was chosen for its high strength, high stiffness, and low coefficient of friction. While the most important property for the couplers is strength, the most important property for the box is stiffness. The problems that some have reported with the standard size Accumate couplers "jamming open" is due specifically to boxes that are either too deep (too much space above or below the coupler shank) or boxes with covers that are too flexible. The amount that the twin shanks of Accumate couplers can offset to open the knuckle is limited by a tiny interlock between the adjacent surfaces of the shanks, and too much clearance allows the interlock peg to come out of its slot and jam against the opposing surface. The parts won't be damaged, but the situation is inconvenient. The standard size Accumates exhibit more problems in this regard than the PROTO version simply because we have no control over the dimensions of the boxes other manufacturers build into their floors.

While both couplers and boxes are made of the same material, they are not made in the same mold; each is in a different tool, one pair of coupler shanks in one and a pair of boxes and covers in another. This is "runnerless" molding, every molecule of plastic we shoot is shipped to you. There are no scrap sprues to be reground and used again, degrading the material properties further with each pass through the molding machine. By using only virgin material in these parts we guarantee that you get all the physical properties the resin manufacturer designed into the material.

Screws:
While it may appear convenient to simply cement the draft gear boxes in place, this will ultimately not have the strength to ensure that the coupler shanks can't spread and jam, therefore we don't recommend any mounting that doesn't have a screw through the boss that the couplers pivot on. As Dr. Anspach pointed out, a 00-90 flathead screw can be used in this location after first lightly countersinking the hole. We chose to go with the 0-80 screw because many people are uncomfortable with working with the smaller size drills, taps, and screws. I did consider incorporating the countersink in the mold and allowing it to be covered by the larger 0-80 pan head, but doing so would only give the 0-80 head bearing outside the area supported by the boss, making it easy to pinch the coupler shanks by over tightening the screw. The box is easy enough to coutersink by hand for those special cars.

Design, Engineering, and Execution:
Dr. Anspach is correct that the PROTO:HO coupler and its draft gear were "engineered" as a system, although since I don't have an engineering degree, I prefer the term designed. And yes, during the building of the tool the core pins that make the mounting holes ended up slightly off center in the bosses. As they say, stuff happens. Since this really doesn't affect the utility of the parts, the decision was made not to do an extensive re-work to the pins. However, the fact that one side of the boss is thinner makes this the first area on the part that doesn't fill, a "short shot". We consider these short shots a defective part, and like any defective Accurail part, we will replace any that are sent to us.

Dimensions and Car Spacing:
The PROTO:HO draft gear was designed to appear to be the continuation of the center sills through the body bolster. The box is designed to match the common 20 1/2" width of center sill cover plates that was common during the late steam / early Diesel era. The detailing on the underside of the box represents the commonly used friction draft gears of the day, contained by the sills, draft lugs, coupler yoke, and yoke support plate. The coupler head itself is a dimensionally accurate model of the AAR Type E coupler, with the knuckle shape modified to allow coupling with the other common magnetic couplers. Since the coupler head is positioned to match the common 3" striker horn to striker plate spacing used with these draft gears , if the end of the draft gear box is positioned where the prototype striker plate is located, the models will have the proper distance between cars. This isn't necessarily where the oversize box provided on some models ends, as none of the manufacturers has really paid much attention to these dimensions in the past, because all the available couplers were oversize. Keep in mind, when modeling more modern prototypes with extended draft gear, long shank couplers, or end of car cushioning devices, that the position of the PROTO:HO box may have to be adjusted to put the coupler pulling face at the proper location.

Mounting on cars without molded on boxes:
Dr. Anspach has given us an excellent summary of how the PROTO:HO box lends itself to mounting on most commercially available equipment, but someone asked about mounting on models where there is no coupler box provided, such as resin kits. The maybe not so obvious answer is to simply use both parts of the box that are provided with the couplers. While the unique design of the Accumate PROTO:HO coupler allows it to be mounted in the box alone, using the surface of the existing box as the cover, press-on covers are provided that when used, yield the same mounting surface dimension as the other popular couplers. These covers are also useful for modeling the extended draft gears on modern cars.

I hope this answers any questions that anyone had.


Dennis Storzek

Dennis (or anyone else),

Has it been determined the practical minimum radius the PROTO:HO couple can
be used for effective operation? I'm thinking literally how tight can the
radius be before it may cause problems for the coupler, not just that it
cope with typical tight radius like 18"

Cheers

David Ball




_____

From: STMFC@... [mailto:STMFC@...] On Behalf Of
Dennis Storzek
Sent: Friday, 14 October 2005 5:39 a.m.
To: STMFC@...
Subject: [STMFC] Accumate Proto:HO couplers


List,

Word of the recent discussion of near scale size couplers and draft gear
boxes finally prompted me to join this forum. I spent some time last night
reading the entire thread, until it was way too late to compose a reply.
I'll try to make comment on all the points raised in this one message.

Material:
Both the Accumate PROTO:HO couplers and boxes are made from acetal
co-polymer engineering resin; either Celcon or its equivelant. This
material was chosen for its high strength, high stiffness, and low
coefficient of friction. While the most important property for the couplers
is strength, the most important property for the box is stiffness. The
problems that some have reported with the standard size Accumate couplers
"jamming open" is due specifically to boxes that are either too deep (too
much space above or below the coupler shank) or boxes with covers that are
too flexible. The amount that the twin shanks of Accumate couplers can
offset to open the knuckle is limited by a tiny interlock between the
adjacent surfaces of the shanks, and too much clearance allows the
interlock peg to come out of its slot and jam against the opposing surface.
The parts won't be damaged, but the situation is inconvenient. The standard
size Accumates exhibit more problems in this regard than the PROTO version
simply because we have no control over the dimensions of the boxes other
manufacturers build into their floors.

While both couplers and boxes are made of the same material, they are not
made in the same mold; each is in a different tool, one pair of coupler
shanks in one and a pair of boxes and covers in another. This is
"runnerless" molding, every molecule of plastic we shoot is shipped to you.
There are no scrap sprues to be reground and used again, degrading the
material properties further with each pass through the molding machine. By
using only virgin material in these parts we guarantee that you get all the
physical properties the resin manufacturer designed into the material.

Screws:
While it may appear convenient to simply cement the draft gear boxes in
place, this will ultimately not have the strength to ensure that the
coupler shanks can't spread and jam, therefore we don't recommend any
mounting that doesn't have a screw through the boss that the couplers pivot
on. As Dr. Anspach pointed out, a 00-90 flathead screw can be used in this
location after first lightly countersinking the hole. We chose to go with
the 0-80 screw because many people are uncomfortable with working with the
smaller size drills, taps, and screws. I did consider incorporating the
countersink in the mold and allowing it to be covered by the larger 0-80
pan head, but doing so would only give the 0-80 head bearing outside the
area supported by the boss, making it easy to pinch the coupler shanks by
over tightening the screw. The box is easy enough to coutersink by hand for
those special cars.

Design, Engineering, and Execution:
Dr. Anspach is correct that the PROTO:HO coupler and its draft gear were
"engineered" as a system, although since I don't have an engineering
degree, I prefer the term designed. And yes, during the building of the
tool the core pins that make the mounting holes ended up slightly off
center in the bosses. As they say, stuff happens. Since this really doesn't
affect the utility of the parts, the decision was made not to do an
extensive re-work to the pins. However, the fact that one side of the boss
is thinner makes this the first area on the part that doesn't fill, a
"short shot". We consider these short shots a defective part, and like any
defective Accurail part, we will replace any that are sent to us.

Dimensions and Car Spacing:
The PROTO:HO draft gear was designed to appear to be the continuation of
the center sills through the body bolster. The box is designed to match the
common 20 1/2" width of center sill cover plates that was common during the
late steam / early Diesel era. The detailing on the underside of the box
represents the commonly used friction draft gears of the day, contained by
the sills, draft lugs, coupler yoke, and yoke support plate. The coupler
head itself is a dimensionally accurate model of the AAR Type E coupler,
with the knuckle shape modified to allow coupling with the other common
magnetic couplers. Since the coupler head is positioned to match the common
3" striker horn to striker plate spacing used with these draft gears , if
the end of the draft gear box is positioned where the prototype striker
plate is located, the models will have the proper distance between cars.
This isn't necessarily where the oversize box provided on some models ends,
as none of the manufacturers has really paid much attention to these
dimensions in the past, because all the available couplers were oversize.
Keep in mind, when modeling more modern prototypes with extended draft
gear, long shank couplers, or end of car cushioning devices, that the
position of the PROTO:HO box may have to be adjusted to put the coupler
pulling face at the proper location.

Mounting on cars without molded on boxes:
Dr. Anspach has given us an excellent summary of how the PROTO:HO box lends
itself to mounting on most commercially available equipment, but someone
asked about mounting on models where there is no coupler box provided, such
as resin kits. The maybe not so obvious answer is to simply use both parts
of the box that are provided with the couplers. While the unique design of
the Accumate PROTO:HO coupler allows it to be mounted in the box alone,
using the surface of the existing box as the cover, press-on covers are
provided that when used, yield the same mounting surface dimension as the
other popular couplers. These covers are also useful for modeling the
extended draft gears on modern cars.

I hope this answers any questions that anyone had.


Dennis Storzek




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_____

--- In STMFC@..., "David Ball" <davidball@x...> wrote:

Dennis (or anyone else),

Has it been determined the practical minimum radius the PROTO:HO couple can
be used for effective operation? I'm thinking literally how tight can the
radius be before it may cause problems for the coupler, not just that it
cope with typical tight radius like 18"

Cheers

David Ball

I was hoping that someone else would jump in here and save me the typing, maybe someone with first hand experience with our PROTO:HO couplers on tight curves, but it doesn't look like that is going to happen.

To be perfectly honest, we've never tried to determine what the practical minimum operating radius is. When you design a product to meet a certain criteria, say operation on 18" or smaller radius curves, you make whatever modifications are necessary to achieve that goal. If the coupler heads need to be overly large, the boxes overly wide, or the narrow boxes artificially flared wider at the opening, that's what you do, and accept those compromises as being necessitated by the original design criteria. The design criteria for the PROTO:HO was simply to put a scale size coupler head on a shank that would fit within the confines of a steam era center sill, and then make it compatible with the other magnetic couplers currently in use. How well it would work on train set radius was a secondary consideration, although the original layout drawings indicate that equal sized cars equipped with the PROTO:HO couplers should be able to negotiate a 15" radius curve. Notice I said equal sized cars. Problems arise when mixing equipment with different amounts of coupler overhand on these tight curves: freight and passenger cars, or freight cars and locomotives. Even a small 0-4-0 will have considerably more distance between the wheels and the coupler, and so this coupler will end up much farther from the track centerline on a sharp curve than the coupler on a freight car. Eighteen inch radius in HO scale is appx. 135' radius on the prototype, 15" radius is appx. 110'. When prototype curves are this tight they are no longer expressed in degrees, but in the actual radius in feet. Railroads build with radii in this range, such as rapid transit operations, typically use wide swinging radial couplers. The interurban railroads that had this sort of curvature used radial couplers on their locomotives so the coupler would follow the coupler on the cars. When these lines were dieselized, they typically needed to use small locomotives such as 44 tonners, which have short wheelbase trucks and minimum coupler overhang. I suspect the same applies to the PROTO:HO couplers.


Dennis Storzek

In regard to tight radius curvature such as found in industrial sidings along the Philadelphia waterfront and other tight locations, the PRR used couplers that had segmented shanks to allow the coupler head to pivot beyond the normal swing left and right. Many engines were equipped with coupler stops to avoid "jackknifing" when the swing became too extreme. This hinged extension allowed operation on curvature that would normally would thwart coupling to cars or pushing movements on these extreme radii.

The crews used to call these "swinging bullnose" couplers. Try to imagine the normal coupler shank as it emerged from the draft gear box, and instead of having the coupler head attached to it, attach the coupler head as a separate piece to the end of the first in a hinged joint which allowed the coupler head to move side to side an additional distance allowing the coupler to stay closer to track center line to compensate for the tight radius that were prevalent in these locations. This arrangement was similar to that which Dennis refers to as being used on the interurban railroads. The PRR used this arrangement on a good many locomotives used in these tight terminal areas such as A5 0-4-0, B6 0-6-0 classes and also on Baldwin and Alco 600HP-1000HP diesels that replaced the steam classes formerly employed in this service. Some of the early rubber-tired street switchers that the Penn employed in the Baltimore area also used this arrangement.

Tom Olsen
7 Boundary Road, West Branch
Newark, Delaware, 19711-7479
(302) 738-4292
tmolsen@...

Dennis Storzek wrote:

--- In STMFC@..., "David Ball" <davidball@x> wrote:
>
> Has it been determined the practical minimum radius the PROTO:HO couple can
> be used for effective operation? I'm thinking literally how tight can the
> radius be before it may cause problems for the coupler,
> David Ball

The
design criteria for the PROTO:HO was simply to put a scale size coupler
head on a shank that would fit within the confines of a steam era center
sill, and then make it compatible with the other magnetic couplers
currently in use. How well it would work on train set radius was a
secondary consideration, although the original layout drawings indicate
that equal sized cars equipped with the PROTO:HO couplers should be able to
negotiate a 15" radius curve.

Dennis Storzek

On the Claremont & Concord in New Hampshire, a former electric railway, due to tight
curvature a 50-foot boxcar could not be placed in the Coy Paper Co. spur unless the
knuckles were removed from the car and the locomotive (a 44-tonner). A steel drawbar
was then used to connect the two, held in place by the knuckle pins. I don't remember how
long the drawbar was (maybe 12-18 inches), but using it gave enough clearance for the
engine and car to negotitate the curve into the mill. Anybody care to try THAT in HO Scale?

Walt Lankenau

Thanks Dennis

Actually, its modelling inteurbans that is the reason why I asked

My principle modelling interest is Pacific Electrics Southern District,
although, my concern doesn't isn't here. - I will be using respectable
modelling track standards, at least for the trackage that carries car load
freight. Pacific Electric just happen to be the subject (I might not even
hang wire)

However that layout for that is years off, and in the mean time I'm
seriously contemplating doing a small portable layout based on freelance
Midwestern interurban, albeit a freight orientated one. This is definitely
be "interurbanish", as its the whole point in building the layout to
demonstrate the subject (not many interurban layouts over here!) This is
will probably mean sharper that 18 inch radius curves for freight trackage.

I know Kadee's in "standard" draft gear boxes can cope with radius of 12
inches (40' cars and less). I realise that using a scale draft gear box is
probably not going to allow something that tight, but I was curious as to
how far they would go. Something I need to consider if I adopt Proto:HO
couples as standard.

Cheer

David Ball



_____

From: STMFC@... [mailto:STMFC@...] On Behalf Of
Dennis Storzek
Sent: Saturday, 22 October 2005 8:26 a.m.
To: STMFC@...
Subject: [STMFC] Re: Accumate Proto:HO couplers


Even a small 0-4-0 will have considerably more distance
between the wheels and the coupler, and so this coupler will end up much
farther from the track centerline on a sharp curve than the coupler on a
freight car. Eighteen inch radius in HO scale is appx. 135' radius on the
prototype, 15" radius is appx. 110'. When prototype curves are this tight
they are no longer expressed in degrees, but in the actual radius in feet.
Railroads build with radii in this range, such as rapid transit operations,
typically use wide swinging radial couplers. The interurban railroads that
had this sort of curvature used radial couplers on their locomotives so the
coupler would follow the coupler on the cars. When these lines were
dieselized, they typically needed to use small locomotives such as 44
tonners, which have short wheelbase trucks and minimum coupler overhang. I
suspect the same applies to the PROTO:HO couplers.


Dennis Storzek



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_____

--- In STMFC@..., "David Ball" <davidball@x...> wrote:

Has it been determined the practical minimum radius the PROTO:HO couple can
be used for effective operation? I'm thinking literally how tight can the
radius be before it may cause problems for the coupler, not just that it
cope with typical tight radius like 18"

Judging by the responses to your question so far, the answer is "no." Might be time to buy
a few sets, do some experimentation, and let us know your findings.

Walt Lankenau