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Whilst we willingly give advice over the phone, we have put some of the most commonly asked questions here for your convenience. If you can't find your answer here - give us a ring.
Table of Contents
- How do you choose the right gravity roller and pitch?
- What is the correct angle for the gravity roller track?
- How do you choose the right width of gravity roller track?
- Can we supply tapered gravity rollers ?
- Are heavy duty plastic gravity rollers available?
- What colours are available ?
- Do we stock gravity rollers ?
- Are the gravity rollers food quality ?
- Chemical compatibility ?
- Where can I get advice and prices ?
- Can I use gravity rollers in powered applications?
How do you pick the right combination of gravity roller and pitch for what is being carried?
A. We want you to get the best performance from our equipment at the best possible price so it is vitally important that you choose the right option. In the simplest case, choose a gravity roller diameter where the rated load of the gravity roller is as close as possible to half the package weight. Now look at the available pitches for this gravity roller diameter and choose the one that is a maximum of half the package length. If the package has a less than rigid base, reduce the pitch to put as many gravity rollers underneath as you can justify. It is inadvisable to divide the load by the number of rollers underneath it where the number of rollers is greater than three, and then choose a roller of this rating because it is unlikely that the load distribution will be even giving a possibility of roller overloading.
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At what angle does the gravity roller conveyor have to be?
A. After many years of experience, we advise that a gravity roller conveyor needs to be at an angle where the package travels down at a steady speed without needing to be pushed to get it started. A rough guide is 2 to 3 degrees (40 to 50 mm of fall per linear metre of run approximately) for plastic rollers and 7 to 9 degrees for steel rollers. This must be increased for light packages, bends or close pitches whilst heavier loads may need this reducing. The final angle must be found by trial and error on installation.
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How wide should the gravity roller conveyor be?
A. Ideally, the inside frame dimension should be slightly greater than the package width. Avoid having the package overhanging the frame as this is considered unsafe. Loads should never be concentrated in the centre of the width but always evenly distributed across it to avoid excessive roller deflections.
If sideguides have been specified, choose a track width that allows plenty of room either side of the load otherwise the friction of the load against the sideguide may stop the load from conveying. Under normal circumstances, sideguides are unnecessary even around bends.
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Can we supply tapered rollers?
A. Tapered rollers are ideal in certain applications as they allow a pack entering the bend squarely to leave the bend squarely. The outer edge of the load can travel faster than the inside edge to allow for the greater distance that it has to traverse in the same time. We can offer tapered rollers but only within certain limits. Tapered gravity rollers are expensive to make and can only be made to match certain dimensions of bend.Almost the same performance can be gained at a fraction of the cost with a skatewheel bend because the wheels on a given axle can rotate at different speeds. Skatewheel bends can be very successful provided that the base of the package is rigid. Please click here for more information [ Wheels ]
Are the plastic gravity rollers available in heavy duty form?
A. Our plastic gravity rollers have been developed over many years to allow free rotation, no lubrication and easy cleaning. These factors are achieved by using plastic races in the bearings which restricts the load rating and the mistreatment that they can sustain. Not all plastic rollers made by other manufacturers are the same although their rollers may look similar. Often there is a steel raced semi-precision bearing hidden behind the plastic end cap housing. This means that they can take more abuse but will suffer corrosion, will have a higher inertia and will create more noise than a plastic raced bearing. If a heavier duty roller is required for a larger load or to survive mistreatment, the steel gravity roller range can offer a solution.
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Can the plastic rollers be supplied in any other colour?
A MML gravity rollers have been tried and tested over many years in their standard light grey colour. However, we have just added a sky blue colour specially for food applications. If you specifically require a colour other than these, for a sufficiently large order quantity we can quote from a range of colours to provide a suitable match for your requirements although please be aware that changing the colour of a plastic tube can alter its mechanical characteristics.
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Do we hold gravity rollers in stock?
A. We offer over two hundred different combinations of plastic gravity rollers alone and each one can be requested in an infinite number of lengths. Complete gravity rollers are therefore not held in stock but are made quickly to order.
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Are the plastic gravity rollers of food quality?
A. Many of our customers happily use our rollers and conveyors in food environments despite there being no British Standard to work to with regards gravity rollers in contact with food. Indeed, many users set their own standards which they are happy that our equipment passes. Most of our plastic gravity rollers are used at the end of line in the packing area and so are considered very suitable since they can be washed down. On the other hand, many more customers have used our plastic gravity rollers in contact with raw food and have been satisfied. In this situation, our ABS* tubing is safer than the more commonly used PVC because it has no tin content. Our bearings have full Food and Drug Administration (USA) certification and the tube material is approved by the British Water Research Council.
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Will the gravity rollers survive in a chemical environment?
A. We choose the best materials for the majority of applications that our equipment is used in. These materials are perfectly suited to ordinary use but where the environment includes chemicals, the effect of that chemical, even cleaning fluids, on gravity rollers is difficult to predict. Our material suppliers produce basic lists of suitability but they specify only certain fluids at certain concentrations and at certain temperatures. The lists may also refer to a slightly different mix of the basic plastic compound or the grade of stainless steel. Gaining more information is virtually impossible so if the chemical is not listed and we have no experience of that combination, the best course of action is to try it and see what happens.
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Where can I get advice and prices?
A. Whilst we have no traveling representative who can visit you, if you can have the basic information to hand – give us a ring on +44 (0) 1606 833 262 for a prompt quotation, fax us a drawing on +44 (0) 1606 832 304 or follow the hyperlink to the pre-prepared quotations page.
For more information click on this hyperlink Contact us
To jump to the quotations page click here Quotations
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Can I use gravity rollers in powered applications?
A. Many of our customers regularly use our gravity rollers (as opposed to grooved/sprocketed rollers intended for this use) to support belts but if you do use them in this way you must remember;
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We do not recommend that you use them in this way and our warranty may well be void. |
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The bearings are only intended for intermittent rotation. Continuous rotation will reduce their life. Particular problems occur with heat build up in the races. |
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Never use gravity rollers as the drums at the ends of belts or a pinch rollers. |
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If there is a precision bearing version of the roller - use that. Otherwise use a heavy duty bearing if available. |
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The operational life of rollers used in this way may be 10 minutes or may be 10 years. It is impossible to predict. |
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*ABS is acrylonitrile butadiene styrene, PVC is polyvinyl chloride, acetal is a mouldable, engineering grade, copolymer.