Frequently asked questions
1. I need chocks with additional height

There are three options if additional height is required in your installation:

A Tall Top Ring

When additional height is required in the range of 5-25 mm, we can supply taller top rings for the RotaChock® BasicLine/SlimLine/Mounting plate. These can replace the ones originally supplied and provide additional height. We stock these taller top rings for the full range at several thicknesses for maximum flexibility.

B Spacer Ring

If required, a spacer ring can be placed underneath the RotaChock® BasicLine & SlimLine and the foundation. 
We stock these Spacer Rings for the full range of several thicknesses for maximum flexibility.

C RotaChock® Tall Line

For specific applications, we recommend using the RotaChock® Tall Line, which has an extended bottom ring. However, there are some considerations for using Tall Line configurations, i.e., when thrust or shear forces are involved.

As a rule of thumb for all three options: the height of the chock should never exceed the diameter. For example, the maximum height of the RC4-BasicLine, which is 102 mm in diameter, should not exceed 102 mm. Maximum height = 53, which means that the maximum allowable additional height is 49 mm. From a design viewpoint, the best option is A. The number of mating surfaces should be minimized because this influences the final clamping force.

2. Can a shim/plate/spacer be added below the RotaChock®?

Yes. However, some care must be taken during installation. Below are some scenarios that we have seen over the years:

There are two prominent design notes for the use of shims/plates/spacers underneath RotaChock®:

  • The foundation and additional plating need to be flat. Any deformation means the installation may warp/bend, resulting in Soft-Foot. Please beware of an increased risk of warping/twisting when one shim/plate is placed under multiple chocks. When torquing the first RotaChock®, the added plate may warp and twist. Note that this may also occur when welding in the immediate vicinity. Heat may deform the steel and result in Soft-Foot. 
  • The number of mating surfaces must be kept to a minimum because this influences the final clamping force. Adding more separate pieces in the clamping assembly should be avoided.

Please check FAQ #1 for our preferred solutions if you need increased height.

5. I need an extended adjustment range, is there a limit to the adjustment height?

We can offer the RotaChock® Extended Adjustment Range (EAR) when more adjustability is required. Like the RotaChock® Tall Line, it has an extended bottom ring, but the EAR also has an extended center ring. The EAR increases the package’s flexibility in the design of the installation or a system that changes during its lifecycle. Please contact your RotaChock® distributor for further details on this product range and its capabilities.

6. How to reduce the height of the RotaChock®?

RotaChock® BasicLine and Spherical Spacer can easily be machined in a lathe. First, install the assembled chock into the lathe’s chuck (only the bottom and center rings). Then remove material from the bottom of both rings simultaneously until you reach the required height. The procedure is part of the classification type approval, so no special permission is required. Note that the adjustment range is also reduced. For every mm you take off, you will lose one mm of adjustment range. At the minimum reduced height, only one mm of adjustment remains. The minimum reduced heights can be found in the RotaChock® dimension charts. If reducing the height is not enough, switch to the RotaChock® SlimLine.

7. How to enlarge the bolt hole of the RotaChock®?

You can find the optional foundation bolt size in the dimension charts; this is the maximum allowed bolt size for the RotaChock® when the bolt hole is enlarged. Rule of thumb: maximum enlargement is optional bolt size + 1 mm. For example, RC2-BasicLine has an inside diameter of Ø17, and the optional bolt size is M18. When adding one mm, the inner diameter can be enlarged to a maximum of Ø19.

8. How much support does the RotaChock® need?

The bottom part should always be entirely supported; not having the base ring supported may distort the base’s thread. The thread diameter of the RotaChock® should be fully underneath the machine foot. Both diameters can be found in the dimension chart.

9. What is the recommended foundation thickness?

A rule of thumb is to match the foundation bolt diameter; if the bolt diameter is 1”, then the foundation should be at least 1” thick. Also, ensure that gussets are used to tie the load path to the foundation. In case of a large engine mass, angle the gussets outwards to increase the foundation’s rigidity.

10. What about i-Beams?

Some installations require cut-outs to be made in i-beam webs to install the foundation bolts; below an example. 

the recess is too large for the chock’s diameter. The removed web material is too close to the mounting flange. The results are a significantly reduced beam strength and system that acts as though it has Soft-Foot. 

this is is an improved access cut-out, which maintains the strength of the mounting flange. Add a spacer to access the nut for ease of maintenance for the lifecycle.

11. Can I tack weld the RotaChock® to the foundation?

Do not weld anything to or around the RotaChock®. Also, avoid welding in the immediate vicinity, as heat may deform the steel structure and open the possibility of Soft-Foot. When welding is required, please ensure proper earthing.

13. How can we use dowel pins in combination with RotaChock®?

You can use a welded riser block or a nut and bolt method like below: When you have completed all the steps from the installation instruction, weld a steel block that is 1 mm lower than the gap near the chock, and drill a hole through the machine foot into the block and install a dowel pin.

19. What is the most significant load in the installation?

The bolt tension is by far the highest load in the installation. In general, around 90% of the total load on the RotaChock® is a result of bolt tension. All other loads, such as machine loads created by weight and torque, are less significant.

20. How is it possible that my foundation bolts are loosening?

The first two questions which we always ask back are: Is there enough stretch in your bolts? Are your bolts straight and not bending? See the design pages on 17 for further instructions. In the field, we experience a high spread on tensioners, in some cases over 40%. Bolt lubrication is also a significant factor. There are several reasons for bolts loosening; contact our engineering team for support.

21. What is the difference between rigid & resilient mounting?
Rigid mounting

All equipment, especially rotating machinery, is required by the manufacturer to be affixed to a structural base. Rigid mounting means creating a solid steel plate (foundation) with a machined top surface, grouted to a concrete foundation or welded to a steel structure, and supporting and maintaining the equipment’s alignment. The gap between the foundation and its machine foot can be filled using several different processes and products. In the philosophy of RotaChock®, it’s our goal to create a rigid coplanar surface for the machine that exceeds the OEM requirements for Soft-Foot, and that must retain the equipment’s position after final alignment.

Resilient mounting

Structure-borne noise and vibration are produced by an engine’s moving parts and the combustion process. These various forms of vibrations like noise, vibration, or shocks cause comfort disturbance onboard ships. Resilient mounts are the most effective option where noise and vibrations transmitted through to the vessel’s hull must be reduced to an absolute minimum. This reduction contributes significantly to crew and passenger comfort, especially on ferries, cruise liners, or yachts.

The installation of resilient mounts can be challenging. The rubber mount’s base plate must be aligned perfectly parallel to the machine foot to ensure optimal vibration damping. Fortunately, we have a solution to that problem. Please check page 13 for detailed information about our RotaChock® Mounting Plate.

23. What is your advice regarding corrosion protection?

The standard RotaChock® types are Anti-Corrosion Enhanced. You will find more information on this process on page 7 of our Information Book wich you can find at our downloads page. We advise stainless steel (316L) for maximum protection against corrosion in extreme environments such as offshore and deck applications. In case of specific corrosion requirements, please contact our engineering team. 

24. Can we use a coating on the RotaChock®?

In some applications, the complete installation is coated, including RotaChock®. Please take caution during application since paint sprayed on the thread can prevent the RotaChock® from rotating.

25. Do you use grease on RotaChock®?

All RotaChock® that are Anti-Corrosion Enhanced undergo a final dip in machine oil. They can still be oily when removed from the packaging. It does not harm the final installation and can be left on the RotaChock®. If preferred, it can be removed with a cloth.

All Stainless Steel RotaChock® have the threads and spherical top parts lubricated with Molykote® D Anti-Seize Paste or similar. This paste should not be removed since it prevents the parts from galling and seizing.

All non-treated (carbon) steel RotaChock® have the threads and spherical top part lubricated with Molykote® P-37 Anti-Seize Paste or similar. It must remain on the RotaChock® when installed. The outer surfaces are coated with LPS 3® Premier Rust Inhibitor or similar. This should be cleaned off the top and base surface of the chock.

26. What about lubricating the foundation bolts?

Many industries and manufacturers have their bolting and lubrication preferences. Changing the lubrication agent impacts the friction coefficient and the resulting tightening torque. No matter what lubrication is used, note that we recommend that the foundation bolt has a minimum bolt stretch of 0,20 mm.

27. How to mount on concrete?

Use a steel plate of sufficient surface and thickness so that the surface pressure on concrete is of an acceptable level. When mounting RotaChock® directly on concrete, first check the existing concrete’s allowable surface pressure.

28. What to do if my RotaChock® is frozen or hard to turn? 

Dirt or debris may have infiltrated the thread of the RotaChock®. Disassemble the chock, inspect the threads, and clean it using a rag and WD-40 or similar. In most cases, this will solve the issue.

In cases where the chock is completely seized (e.g., because grease in the threads has solidified due to a reaction with cleaning solutions used to degrease the equipment), remove the chock and carefully apply heat (never exceed 250C/480F). Heat will cause the grease to liquefy. Thoroughly clean the threads and use a nickel-based anti-seize before reinstallation. 

Spotted some damage to the thread? Obtain a set of working spares from your warehouse. Have ready access to a set of spares. Take out the old chock and replace it with a working set and finish the job. Back at the shop, refurbish the old chocks at your leisure and set them up for the next occasion.

29. Should I perform a Soft-Foot check after installing RotaChock®? 

If the design and installation instructions of RotaChock® are followed, a Soft-Foot should not be possible. However, if a final Soft-Foot check is preferred, these are the instructions:

  • After final alignment, when the bolts have been tightened to the final torque, install a dial indicator near bolt position #1 and set it to zero
  • When loosening the bolt, the indicator should not move more than 0,05 mm/0,002.”
  • If the indicator moves more than 0,05 mm/0,002”, repeat the alignment and recheck your bolting plan
30. During service life, do I have to check the RotaChock®?

The RotaChock® itself does not have to be checked during service. We advise following the OEM maintenance instructions and guidelines for checking the mounting fasteners’ torque. Without OEM guidelines, we recommend that the mounting fasteners’ torque is checked after 100 hours of normal load operations.

31. What is most cost-effective: epoxy resin, steel-fitted blocks, or RotaChock®?

RotaChock® is the most cost-effective and the best lifecycle decision for rotating equipment. Soft-Foot is solved, and your equipment can be realigned at any required moment. Our engineering team has decades of experience with aligning and mounting machines and has worked with many other chocking products. If not convinced, we encourage you to sit down with us and prepare a cost comparison between epoxy resins, steel-fitted blocks, and RotaChock®.

32. What is the shelf life for RotaChock®?

People are often confused because they have experience with epoxy resins, where it’s essential to check the date of production before mixing. However, RotaChock is made of steel and will not lose its mechanical properties or deteriorate. Therefore, RotaChock® has no expiry date and has an unlimited shelf life. Carbon steel is the world’s most recycled material and can be reused indefinitely without loss of mechanical properties. Due to its durability, RotaChock® has a long service life and can be recycled and used in other products, saving resources in the process. Note: RotaChock should be stored under dry conditions and in its original packaging.