Spit Rod Selection and Loading Capacity

Spit Rod Capacity

One of the most common questions is, “How much can the spit rod hold”. Of course as with so many things these days, that is a loaded question (no pun intended).

We have begun to accumulate the data for you in a meaningful way that should help you make the best decision based on your cooking intentions.

We will focus on the two most popular rod sizes which are 5/16” square and ½” hex. There are a number of ways to load a spit rod and that will be taken into account. You can put your item in the center or you can put it on the side very close to the wall. When cooking 2 chickens for example you will see it is better to have them on the sides away from the middle as you would expect.

One thing that we must consider when loading a rod is that we do not flex it too much while it is rotating. The concern here is that we are applying unwanted forces to the motor. Instead of the rod simply going into the square drive hole, it will when overloaded, pry on the hole, applying excessive side loads. It will also induce high levels of stress into the final output section and cause premature gear failure. In addition you will be overheating the motor and causing it to fail early.

Since there are literally thousands of grills in existence and also a vast number of custom and homemade units, it would be impossible to consider all the possibilities. Fortunately there are far less spit rod length selections. Once you take away some somewhat common dimensions you are left with a lot fewer possibilities.

When considering the load, the factors are relatively simple. The size of the rod and how the rod is supported are the first issues. In addition you will have to consider how the item is placed along its length. A final issue is the item itself and we will not dwell on that heavily in this article. That being whether it is simply meat like a chicken or a basket which has its own built in support structure. A basket can move the loading points toward the outside and increase the amount of food you could put on the spit rod.

In the following chart you will see that we are looking at rod deflection distance. The distance is measured half way between the support distances. The support distance simulates your grill base or bracket support locations. We consider a deflection of less than .100 or 1/10 of an inch acceptable. Any more than this and you begin to affect the performance and life of the motor. Deflection of more than .125 or 1/8 of an inch should be avoided.

1 Bird loaded in center of spit rod or on side using forks.
Item Weight	Rod Shape	Rod Size	Rod Support Distance	Item	Deflection Center Loaded	Deflection Side Loaded
	Actual weight was 1/2# more to account for forks
5#	Hex	1/2"	27 Inches	1 Bird	0.024	0.016
10#	Hex	1/2"	27 Inches	1 Bird	0.048	0.03
12#	Hex	1/2"	27 Inches	1 Bird	0.057	0.037
14#	Hex	1/2"	27 Inches	1 Bird	0.064	0.042
15#	Hex	1/2"	27 Inches	1 Bird	0.066	0.048
16#	Hex	1/2"	27 Inches	1 Bird	0.070	0.054
18#	Hex	1/2"	27 Inches	1 Bird	0.082	0.06
20#	Hex	1/2"	27 Inches	1 Bird	0.092	0.07
22#	Hex	1/2"	27 Inches	1 Bird	0.099	0.08
24#	Hex	1/2"	27 Inches	1 Bird	0.108	0.091
26#	Hex	1/2"	27 Inches	1 Bird	0.120	0.103
1 Bird loaded in center of spit rod or on side using forks.
Item Weight	Rod Shape	Rod Size	Rod Support Distance	Item	Deflection Center Loaded	Deflection Side Loaded
	Actual weight was 1/2# more to account for forks
5#	Square	5/16"	27 Inches	1 Bird	0.090	0.062
2 - 5# Birds ( 1 each side)  (nothing in center) with forks.
Item Weight	Rod Shape	Rod Size	Rod Support Distance	Item	N/A	Deflection Side Loaded
	Actual weight was 1/2# more to account for forks
5# each	Square	5/16"	27 Inches	2 Birds		0.10

As you can see the 5/16” rods are very limited in their capacity and extra care is needed when loading them.  More data to follow.