Jastram Model B Steering Gear

Jastram B Model Actuators are double-acting equal displacement cylinders, which are directly connected to a tiller. When the B Model is actuated it moves the tiller, which in turn moves the rudder.

The actuator sizing is primarily dependent on the maximum rudder torque required. Once the required rudder torque is known the appropriate actuator size can be selected.

Calculating the rudder torque is complex. An incorrect calculation can result in failure of the steering system. Torque calculations should be confirmed by a naval architect or designer.
 

 

Actuator & Helm Pump Sizes
Actuators					Helm Pumps		Torque ~ 2 x 35' @ 1000 PSI		Max Rudder Stock ø
Part #	B Model	Qty	Displacement		Model	Wheel Turns	Lbs-Ft	N-M	In	mm
			In³	cm³
JA-101022-1	B-38-120	1	6.9	113	H20	3½	391	530	1.88	48
	B-38-120	2	13.8	226	H26	5½	783	1062	1.88	48
JA-101022-2	B-38-190	1	10.9	179	H20	5½	620	841	1.88	48
	B-38-190	2	21.8	358	H36	6	1239	1680	1.88	48
JA-101019-1	B-50-190	1	20.2	331	H36	5½	1145	1552	1.88	79
	B-50-190	2	40.4	662	H60	6½	2291	3106	3.13	79
JA-101019-2	B-50-300	1	31.9	523	H60	5½	1808	2451	3.13	79
	B-50-300	2	63.8	1046	H90	7	3617	4904	3.13	79
JA-101020-1	B-76-190	1	43.7	716	H60	7¼	2478	3360	3.13	79
	B-76-190	2	87.4	1432	H90	9¾	4956	6719	3.13	79
JA-101020-4	B-76-230	1	52.9	867	H90	6	3148	4268	3.13	79
	B-76-230	2	105.8	1734	H90	12	6296	8536	3.13	79
JA-101020-2	B-76-300	1	68.9	1129	H90	7½	3913	5305	3.13	79
	B-76-300	2	137.8	2258	H90	15½	7826	10611	3.13	79
JA-101020-3	B-76-400	1	93.4	1531	H90	10½	5301	7187	4.13	105
	B-76-400	2	186.9	3062	H90	20¾	10601	14373	4.13	105

Items to note on small steering systems:

• Double Acting Relief and Bypass (DARBs) valves are suggested to protect the steering gear

• Header tanks or autofill valves are suggested to prevent the introduction of air or the loss of steering due to low oil levels

• A system pressure of around 500 PSI (35 BAR) is suggested for manual steering systems

• Shut off valves are suggested at each component in the hydraulic circuit

• Tube or pipe sizing is based on the helm pump information, see Jastram H Model Helm Pump Cutsheet for details

Jastram Actuators require the following items for installation:

• Tiller bolts

• Hoses

Jastram Actuators are serviceable. Standard seal kits are available and should be changed regularly:

• JA-950002-1, B-38 seal kit

• JA-950003-1, B-50 seal kit

• JA-950004-1, B-76 seal kit
 

Steering System Specifications
Actuator Model	A	B	C	D	E	F	G	H	I	J	K	L *max	M	N	O	P	T	U
B-38-120	404	80	100	545	75	32	46	37	21	17	140	48	257	82	50	10	16	SAE
B-38-190	509	126	158	723	75	32	46	37	21	17	140	48	257	82	50	10	16	-4
B-50-190	541	126	158	746	86	55	48	76	37	25	148	79	360	90	62	13	22	SAE
B-50-300	699	199	249	1020	86	55	48	76	37	25	148	79	360	90	62	13	22	-6
B-76-190	644	126	158	878	126	75	72	76	37	38	148	79	360	115	95	16	32
B-76-230	672	153	191	972	126	75	72	76	37	38	148	79	360	115	95	16	32	SAE
B-76-300	806	199	249	1160	126	75	72	76	37	38	148	79	360	115	95	16	32	-8
B-76-400	961	270	338	1416	126	75	72	98	49	38	198	105	475	115	95	16	32
TORQUE RATING IS DETERMINED AT 1000 PSI (69 BAR) AND 35°, MAXIMUM RUDDER ANGLE 37°