Bike rack limitation - options to improve

[John Timberlake]

Hello Funsters,

Moving to heavier e-bikes now; the current stated max load of my current carrier is 60 kg.

Now, apart from the risk of a hernia humping a 35k e-bike up to chest height to get it on, the problem is I will have two of the blighters to contend with, so 70 kg in total.

I'm thinking of adding support bars from the chassis up to the rack - will this suffice ? or do I risk the back of the motorhome being ripped off. I live in Belgium and the roads are notoriously bumpy (shit).

Basically, is the 60kg max related to the actual carrier, or the mountings themselves on the motorhome? I assume some leeway is built in.

Cheers

 

[David and Sally]

I wouldn’t even think of doing anything. Can you take off the batteries off or is the 35kg with them off?
Overloading or modifying your bike rack would not go down well in the event of something failing and causing a serious incident.

 

[Phill D]

It’s not only the rack that needs supporting, you need to look at what the rack is fixed too and will that take the additional load, particularly on bumpy roads.

 

[scotzsue]

Our ebikes without batteries are just over 50K, we use a tow bar mounted carrier, so much easier but still takes 2 to lift them on because of the design. Modified Halfords was originally for 3 bikes.

 

[Phill D]

As far as lifting the bikes are concerned the way around that is with step or a carry bike rack 77!

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[Two on Tour]

I changed over to a Fiamma Lift 77 E-Bike as I was having to lift our e-bikes onto our previous bike rack using a step, and I could see that it was only a matter of time before the step would wobble, and I would end up flat on my back with a bike on top of me.
I wind our Fiamma Lift 77 up and down with my cordless drill.

 

[Two on Tour]

It’s not only the rack that needs supporting, you need to look at what the rack is fixed too and will that take the additional load, particularly on bumpy roads.

We have a bathroom across the back of our van, and I noticed that with our E-bikes on our bike rack the back wall of our van move away from the washbasin by a couple of mm, and of course this gap would be greater as we hit bumps and potholes in the road.
I fitted Fiamma mounting bars which spread the weight over a bigger area across the back of our van top and bottom rather than just the original 4 small points, and now we have no deflection in our back wall at all.

 

[Coolcats]

Hello Funsters,

Moving to heavier e-bikes now; the current stated max load of my current carrier is 60 kg.

Now, apart from the risk of a hernia humping a 35k e-bike up to chest height to get it on, the problem is I will have two of the blighters to contend with, so 70 kg in total.

I'm thinking of adding support bars from the chassis up to the rack - will this suffice ? or do I risk the back of the motorhome being ripped off. I live in Belgium and the roads are notoriously bumpy (shit).

Basically, is the 60kg max related to the actual carrier, or the mountings themselves on the motorhome? I assume some leeway is built in.

Cheers

phew those are heavy bikes would it be worth changing them for lighter ones such as the Whyte RHeO ? As they are about 20 kilo per bike lighter

RHeO 2 eCity and leisure bike

Flow effortlessly, everywhereLightweight, comfortable and capable, the all-new RHeO 2 ebike gives you the boost to flow wherever you choose with ease.The powerful hub motor delivers three levels of support to flatten any hill, and the 250Wh internal battery delivers plenty of range for heading...

whytebikes.com

 

[John Timberlake]

They are 35 kg with the battery removed.

I've just ordered the 1st one, and it should arrive today. I'll see if I can remove some other bits (saddle, rack).

Otherwise, a stronger rack, as suggested.

 

[Orion]

Do you have a towbar fitted to your Moho? If not, you considered one as it opens up a number of options other than towing.

The rear elevation of our Adria came with the pre-installation done for a bike rack to be fitted, but I wouldn’t consider one due to the loading on the wall - plus the hassle of lifting them up onto it.

All our recent vehicles have had towbars for various reasons, so a Thule tilting tow ball mounted carrier has done sterling service over the years switching between them - including a stint on a VW Amarok 4x4 over off-road terrain where it remained solidly fixed - and it’s now in use on the Adria.

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[Palough]

From an engineering perspective one should consider this.

The equilibrium of a MH can be equated to a child's Seesaw with the back wheels being the fulcrum or pivot point.

The centre of gravity of most MH's is not in the middle between the wheels, but located more towards the back wheels.

In my MH on a weighbridge it's about a 60-40% split, which is why it is so easy to get front wheel spin in a MH starting on a slope, slippery, or not.

This effect becomes more pronounced the longer the overhang of the MH past the centre of the back wheels.

Consider the MH suspended in thin air, with the MH trying rotate clockwise about the rear wheels due to the centre of gravity weight trying to rotate the MH anti-clockwise.

These two clockwise and anti-clockwise forces are balanced by the upwards force of the road on the front wheels, which results in front wheel traction when we drive.

Any additional weight we put on the MH behind the back wheels adds to the anti-clockwise force, thus tending to lift the front wheels off the ground until we reach the point where we have no traction.

As we continue to add weight behind the back wheels, we eventually reach a point where the front wheels leave the ground and there is no traction.

So, considering that MH manufacturers don't seem to concern themselves very much about the engineering principles of weight distribution, (as clearly evidenced by some of the MH's with enormous rear overhang), I'm very conscious of how much heavy stuff I cram into the rear garage.

Depending on the relationship between the lever-arm principles above, an extra 30kg hanging off the back wall, or tow bar, could result in much more than 30kg uplift on the front driving wheels and reduced traction.

Not nice on wet slippery roads, or ice, when you need all the weight one can possibly have over the front wheels!

I noticed the post about the bikes moving the back wall in a MH, and fitting a long bike rack rail across the back stopped the movement.

This is because the rotating force of the bikes is now transferred into the side walls of the MH, which can withstand the force, whereas the flat back wall was being pulled away from the sidewalls.

Hope the above sheds some light on adding extra weight behind the back wheels of an MH, which can have unintended consequences

Some elementary thoughts from a structural Engineer

 

[Ridgeway]

35kgs without battery

E-bicycle or E-mopeds ?

 

[haganap]

No way is would be putting that weight on the back of a motorhome,.asking for trouble.
I have a garage and a towbar mounted bike rack.

 

[dunnah01]

From an engineering perspective one should consider this.

The equilibrium of a MH can be equated to a child's Seesaw with the back wheels being the fulcrum or pivot point.

The centre of gravity of most MH's is not in the middle between the wheels, but located more towards the back wheels.

In my MH on a weighbridge it's about a 60-40% split, which is why it is so easy to get front wheel spin in a MH starting on a slope, slippery, or not.

This effect becomes more pronounced the longer the overhang of the MH past the centre of the back wheels.

Consider the MH suspended in thin air, with the MH trying rotate clockwise about the rear wheels due to the centre of gravity weight trying to rotate the MH anti-clockwise.

These two clockwise and anti-clockwise forces are balanced by the upwards force of the road on the front wheels, which results in front wheel traction when we drive.

Any additional weight we put on the MH behind the back wheels adds to the anti-clockwise force, thus tending to lift the front wheels off the ground until we reach the point where we have no traction.

As we continue to add weight behind the back wheels, we eventually reach a point where the front wheels leave the ground and there is no traction.

So, considering that MH manufacturers don't seem to concern themselves very much about the engineering principles of weight distribution, (as clearly evidenced by some of the MH's with enormous rear overhang), I'm very conscious of how much heavy stuff I cram into the rear garage.

Depending on the relationship between the lever-arm principles above, an extra 30kg hanging off the back wall, or tow bar, could result in much more than 30kg uplift on the front driving wheels and reduced traction.

Not nice on wet slippery roads, or ice, when you need all the weight one can possibly have over the front wheels!

I noticed the post about the bikes moving the back wall in a MH, and fitting a long bike rack rail across the back stopped the movement.

This is because the rotating force of the bikes is now transferred into the side walls of the MH, which can withstand the force, whereas the flat back wall was being pulled away from the sidewalls.

Hope the above sheds some light on adding extra weight behind the back wheels of an MH, which can have unintended consequences

Some elementary thoughts from a structural Engineer

I agree with the taking moments about the axles to determine the vertical forces, but the bit about the back wall doesn't sound quite right. Surely the bar has essentially transformed the back wall loading into a near UDL rather than a pair of point loads so the maximum moment in the wall has been reduced to wl2/8 but the force (or action) in the side wall supports is pretty much the same

 

[Palough]

I agree with the taking moments about the axles to determine the vertical forces, but the bit about the back wall doesn't sound quite right. Surely the bar has essentially transformed the back wall loading into a near UDL rather than a pair of point loads so the maximum moment in the wall has been reduced to wl2/8 but the force (or action) in the side wall supports is pretty much the same

Hi,

What you say is correct, but only partly so, with qualifications, that don't appear to be the situation from the photo.

Firstly, looking at the photo, there doesn't appear to be any restraints along the length of the rail fixing the rail to the back wall, except at the ends, which would then, being screwed into the side wall transfer the forces imposed by the bike rack into tension forces in the side wall.

For the loading to be a UDL, and the reactions to be WL²/8, (as you suggested), the strengthening rail MUST be continuously attached to the rear wall along its entire length.

I don't see any such fastening of the strengthening rail to the back wall along its entire length, only fastening at the ends.

Without fixing the rail into the side walls there is nothing to prevent the back wall from being pulled off the sidewalls, and in the extreme event, completely detatching itself.

The back wall is held in position by attaching it to the peripheral walls (sidewalls, floor and roof).

The strengthening rail, if we can call it that, serves no useful purpose whatsoever unless it is also secured to the periphal walls.

Peter
M.I.E. (Aust.), C.P. Eng.
(Structural Engineer,)

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[kevino]

Get lighter ebikes! Ribble do great ones at 15kg ALe or my FLX is available at a very reasonable cost

 

[dunnah01]

Hi,

What you say is correct, but only partly so, with qualifications, that don't appear to be the situation from the photo.

Firstly, looking at the photo, there doesn't appear to be any restraints along the length of the rail fixing the rail to the back wall, except at the ends, which would then, being screwed into the side wall transfer the forces imposed by the bike rack into tension forces in the side wall.

For the loading to be a UDL, and the reactions to be WL²/8, (as you suggested), the strengthening rail MUST be continuously attached to the rear wall along its entire length.

I don't see any such fastening of the strengthening rail to the back wall along its entire length, only fastening at the ends.

Without fixing the rail into the side walls there is nothing to prevent the back wall from being pulled off the sidewalls, and in the extreme event, completely detatching itself.

The back wall is held in position by attaching it to the peripheral walls (sidewalls, floor and roof).

The strengthening rail, if we can call it that, serves no useful purpose whatsoever unless it is also secured to the periphal walls.

Peter
M.I.E. (Aust.), C.P. Eng.
(Structural Engineer,)

Not sure about the rail above but the Fiamma rail has fixings through the back wall at about 600mm c/c.

 

[Lenny HB]

They are 35 kg with the battery removed.

I've just ordered the 1st one, and it should arrive today. I'll see if I can remove some other bits (saddle, rack).

Otherwise, a stronger rack, as suggested.

What are they made from cast iron?
Never seen an e bike that heavy, my latest one 23.5kg with a 70nm motor & 710 watt battery.

 

[Nanniemate]

I chose a light bike rather than heavey bike and a towbar.
Being 5'2" I am happy to lift my ebike chest height. It's 15kgs with battery

 

[Palough]

Not sure about the rail above but the Fiamma rail has fixings through the back wall at about 600mm c/c.

Hi,

Then without fastening the rail into the side walls, with 600mm spacing across an approximately 2,500 mm wide rear wall, (without fastening into the sidewalls), what we have is 4 concentrated point loads, not a UDL

So what the rail then does, is simply prevent "deflection", (bowing), of the rear wall.

The upside to this is, (if the rail is not fastened into the side walls), the transverse rail will ensure, that when the back wall lands on the bitumen road, the wall will be flat across the back, with no deflection, (bowing), of the wall due to the load that ripped the wall off the back of the MH

Without fastenings into the pheriphal walls, (vertical sidewalls, bottom flooring and roof timber), there is absolutely nothing holding the rear wall in position on the back of the van, and under acceleration it would simply fall onto the road

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[dunnah01]

Hi,

Then without fastening the rail into the side walls, with 600mm spacing across an approximately 2,500 mm wide rear wall, (without fastening into the sidewalls), what we have is 4 concentrated point loads, not a UDL

So what the rail then does, is simply prevent "deflection", (bowing), of the rear wall.

The upside to this is, (if the rail is not fastened into the side walls), the transverse rail will ensure, that when the back wall lands on the bitumen road, the wall will be flat across the back, with no deflection, (bowing), of the wall due to the load that ripped the wall off the back of the MH

Without fastenings into the pheriphal walls, (vertical sidewalls, bottom flooring and roof timber), there is absolutely nothing holding the rear wall in position on the back of the van, and under acceleration it would simply fall onto the road

The OPs problem was the back wall flexing, not coming away from the side walls.

 

[John Timberlake]

What are they made from cast iron?
Never seen an e bike that heavy, my latest one 23.5kg with a 70nm motor & 710 watt battery.

Fat tire electric bicycle | 48V 20Ah battery | Dual motor 2x1000W

Puluma PH003 equipped with two powerful 1000W engines, this off-road beast is ready to conquer any terrain at any time. 26 inch X4.0 fat wheels, dual suspension. The speed can reach 25KM/h and the range is 80KM

www.pulumabike.com

I've decided, for safety reasons, better weight distribution, and the avoidance of open air sleeping, to put them in the garage (just need to remove front wheels, easily done.

The one in the link above is 36kg without battery, 2 x 95 Nm motors, (960Wh battery). Other (Shengmilo S700 5kg lighter).

Very heavy indeed, but solid Might prevent some skinny oiks trying to do a runner with them.

Top speed is definitely not 25 km/h as stated, I can assure you. It's more like 50-60 km/h (haven't had the time, or been brave enough to find out. 50-60, uphill. Jesus.

 

[pandas]

They are 35 kg with the battery removed.

I've just ordered the 1st one, and it should arrive today. I'll see if I can remove some other bits (saddle, rack).

Otherwise, a stronger rack, as suggested.

Most e-bikes we have looked at, and our latest, are around 20kg with the battery removed which is within the 50kg max load recommended for a rear mounted bike rack. Not sure a seat post and rack would reduce the weight sufficiently to be of much help. A transverse trailer maybe?

 

[Ridgeway]

Fat tire electric bicycle | 48V 20Ah battery | Dual motor 2x1000W

Puluma PH003 equipped with two powerful 1000W engines, this off-road beast is ready to conquer any terrain at any time. 26 inch X4.0 fat wheels, dual suspension. The speed can reach 25KM/h and the range is 80KM

www.pulumabike.com

I've decided, for safety reasons, better weight distribution, and the avoidance of open air sleeping, to put them in the garage (just need to remove front wheels, easily done.

The one in the link above is 36kg without battery, 2 x 95 Nm motors, (960Wh battery). Other (Shengmilo S700 5kg lighter).

Very heavy indeed, but solid Might prevent some skinny oiks trying to do a runner with them.

Top speed is definitely not 25 km/h as stated, I can assure you. It's more like 50-60 km/h (haven't had the time, or been brave enough to find out. 50-60, uphill. Jesus.

Well that is a beast ! I can see why it weighs that much now. What does is weigh with batteries ?

 

[John Timberlake]

Well that is a beast ! I can see why it weighs that much now. What does is weigh with batteries ?

41 kg. Wheels with tyres must be about 7-8 kg each.

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