The product has evolved into three different models, depending upon several different factors.  In the product chart below are photographs of each. The original product is in the second column and to install requires the drilling of holes in a specific pattern in the firewall.  An aluminum plate with integral nuts is attached to the rear of the firewall with two screws.  To then install the control, it is passed through the large hole, including the two loose square clamps; and attached at each end, thus determining the ideal path through the firewall.

Next, the two half-balls are placed around the cable and against the firewall.  Lastly the four screws attach the two square clamps over the ball halves and the assembly is tightened in place.  The two ball halves are made from aluminum and provide the objectives of better fire protection and cable positioning.

For use on certificated aircraft the FAA requires firewall components to withstand temperatures above the melting point of aluminum and thus the steel ball, “S” model was developed, and is shown in the third column.  It is identical to the original with the exception of the substitution of steel for aluminum in the ball, and more extensive metal removal from the ball to reduce the added weight of the steel.  Thus the product has a higher cost of manufacture.  

It was learned from field experience that to install the original design on an aircraft with the engine and accessories installed it became difficult to accurately position the required holes.  A product that would require only one hole would greatly reduce this problem.

The product in the first column meets this need.  It requires only one larger hole that is easily made with a common ¾ inch thin-wall electrical conduit punch, a tool common to electrical contractors.  It is a more complex part to manufacture and thus is slightly more expensive.  It is used on experimental aircraft since it is an all aluminum product.

PRODUCT SELECTION

The chart below lists the various properties of the products, including hole sizes available, weights, applications, and pricing.  It should be noted that the ball holes may be enlarged by carefully drilling in small increment sizes.  This is done by assembling the product, clamping it securely in a machine vice, and drilling on a drill press. 

The Spherical Metal Grommet Product Line PART NUMBER TTP-XXXA TTP-XXXB TTP-XXXS   (Rear view) BALL MATERIAL ALUMINUM ALUMINUM STEEL APPROXIMATE WEIGHT 0.12# 0.10# 0.11# PRICE $36.00 $29.00 $34.00 The 3 "X"s in the part number designate the ball hole size in thousandths inches diameter. (The zero and decimal are not part of the three X designation. Example: A TTP-188A has a hole size of 0.188 diameter). Standard sizes below. 125, 188, 240, 250, 260, 312, 375 All aluminum ball holes may be customer enlarged to 0.562 inches. Steel balls smaller than size 0.260 may be enlarged to 0.260. Ball hole sizes larger than 0.260 may be enlarged to 0.562 inches.

PURCHASING

Shipping may be by UPS or US Post.  UPS shipped ground is flat $10, but insured only to $100.  For more insurance please ask for quote.  Shipping by US Post is a flat $3 with no insurance or tracking.  For insurance please ask for quote.